What Theory Explains The Underlying Reasons For The Periodic Law?

What theory explains the underlying reasons for the periodic law? The periodic law was based on the observation that the properties of elements recur and certain elements have similar properties. The theory that explains the existence of the periodic law is quantum mechanical theory.

What is the periodic law based on?

Problems – 1 ) The periodic law states that

similar properties recur periodically when elements are arranged according to increasing atomic number
similar properties recur periodically when elements are arranged according to increasing atomic weight
similar properties are everywhere on the periodic table
elements in the same period have same characteristics

2 ) Which element is most similar to Sodium

Potassium
Aluminum
Oxygen
Calcium

3) According to the periodic law, would argon be in front of potassium or after? Explain why.4) Which element is most similar to Calcium?

Carbon
Oxygen
Strontium
Iodine

5) Who were the two chemists that came up with the periodic law?

John Dalton and Michael Faraday
Dmitri Mendeleev and Lothar Meyer
Michael Faraday and Lothar Meyer
John Dalton and Dmitri Mendeleev

What is the periodic theory?

More on the Mendeleev’s Periodic Table – The similarities among macroscopic properties within each of the chemical families lead one to expect microscopic similarities as well. Atoms of sodium ought to be similar in some way to atoms of lithium, potassium, and the other alkali metals.

This could account for the related chemical reactivities and analogous compounds of these elements.
According to Dalton’s atomic theory, different kinds of atoms may be distinguished by their relative masses (atomic weights).
Therefore it seems reasonable to expect some correlation between this microscopic property and macroscopic chemical behavior.

You can see that such a relationship exist by listing symbols for the first dozen elements in order of increasing relative mass. Obtaining atomic weights, we have Elements which belong to families we have already discussed are indicated by shading around their symbols. The second, third, and forth elements on the list (He, Li, and Be) are a noble gas, an alkali metal, and an alkaline-earth metal, respectively. Exactly the same sequence is repeated eight elements later (Ne, Na, and Mg), but this time a halogen (F) precedes the noble gas.

If a list were made of all elements, we would find the sequence halogen, noble gas, alkali metal, and alkaline-earth metal several more times.
Dmitri Ivanovich Mendeleev proposed the periodic law behind his periodic table compiling.
This law states that when the elements are listed in order of increasing atomic weights, their properties vary periodically,

That is, similar elements do not have similar atomic weights. Rather, as we go down a list of elements in order of atomic weights, corresponding properties are observed at regular intervals. To emphasize this periodic repetition of similar properties, Mendeleev arranged the symbols and atomic weights of the elements in the table shown below.

Each vertical column of this periodic table contains a group or family of related elements.
The alkali metals are in group I ( Gruppe I), alkaline earths in group II, chalcogens in group VI, and halogens in group VII.
Mendeleev was not quite sure where to put the coinage metals, and so they appear twice.

Each time, however, copper, silver, and gold are arranged in a vertical column. The noble gases were discovered nearly a quarter century after Mendeleev’s first periodic table was published, but they, too, fit the periodic arrangement. In constructing his table, Mendeleev found that sometimes there were not enough elements to fill all the available spaces in each horizontal row or period, What Theory Explains The Underlying Reasons For The Periodic Law Figure \(\PageIndex \): Mendeleev’s periodic table, redrawn from Annalen der Chemie, supplemental volume 8, 1872. The German words Gruppe and Reihen indicate, respectively, the groups and rows (or periods) in the table. Mendeleev also used the European convention of a comma instead of a period for the decimal and J instead I for iodine.

The noble gases had not yet been discovered when Mendeleev devised the periodic table, and are thus not displayed.
As an example of this predictive process, look at the fourth numbered row ( Reihen ).
Scandium (Sc) was unknown in 1872; so titanium (Ti) followed calcium (Ca) in order of atomic weights.

This would have placed titanium below boron (B) in group III, but Mendeleev knew that the most common oxide of titanium, TiO 2, had a formula similar to an oxide of carbon CO 2, rather than of boron, B 2 O 3, Therefore he placed titanium below carbon in group IV.

He proposed that an undiscovered element, ekaboron, would eventually be found to fit below boron.
The prefix eka means “below.”) Properties predicted for ekaboron are shown in the following table.
They agreed remarkably with those measured experimentally for scandium when it was discovered 7 years later.

This agreement was convincing evidence that a periodic table is a good way to summarize a great many macroscopic, experimental facts.

Table \(\PageIndex \): Comparison of Mendeleev’s Predictions with the Observed Properties of the Element Scandium.


Property	Properties Predicted for Ekaboron (Eb)* by Mendeleev 1872	Properties Found for Scandium after its Discovery in 1879
Atomic weight	44	44†
Formula of oxide	Eb 2 O 3	Sc 2 O 3
Density of oxide	3.5	3.86
Acidity of oxide	Greater than MgO	Greater than MgO
Formula of chloride	EbCl 3	ScCl 3
Boiling point of chloride	Higher than for	Higher than for
Color of compounds	Colorless	Colorless

Mendeleev used the name ”eka”boron because the blank space into which the element should fit was ”below” boron in his periodic table. † The modern value of the atomic weight of scandium is 44.96. The modern periodic table differs in some ways from Mendeleev’s original version.

It contains more than 40 additional elements, and its rows are longer instead of being squeezed under one another in staggered columns.
For example, Mendeleev’s fourth and fifth rows are both contained in the fourth period of the modern table.
This ends up placing gallium, not scandium underneath boron in the periodic table.

This rearrangement is due to theory on the electronic structure of atoms, in particular ideas about orbitals and the relation of electronic configuration to the periodic table. The extremely important idea of vertical groups of related elements is still retained, as are Mendeleev’s group numbers.

The latter appear as roman numerals at the top of each column in the modern table. Mendeleev was an extraordinary chemist that was able to compile the greatest chemical instrument of all time. He was not alone in compiling the elements, and many other great chemists contributed too. The idea of elements began over 5,000 years ago and started to finally take shape a mere 200 years ago with Mendeleev’s periodic table.

Yet, it was not the end of the formation of the periodic table. It has changed over time, and with continue to transform as more and more elements are discovered.

Who proposed the law of periodicity?

Classification of the Elements in the Periodic Table: – Classification of the elements in the periodic table can be done in four ways on the basis of their electronic configurations: Elements of group 18 of the modern periodic table are considered a,

The electronic configuration of the first element (helium) of this group is 1s 2, Rest all the elements (neon, argon, krypton, xenon, and radon) have their outer shell electronic configuration is ns2np6. As the octet of these elements is complete, hence they are highly stable elements. S-lock and come under the category of representative elements.

Elements in groups 1 and 2 are known as the s – block elements (elements with 1s 2 and 2s 2 outermost configuration). Group 13-17 are known as the p-block elements (outermost configuration varies from ns2np1 to ns 2 np 5 ). Elements which belong to group 3 to 12 and have their outer shell electronic configuration as (n-1)d 1-10 ns 1-2 are referred to as transition elements.

These elements are also known as the d-block elements.
Lanthanides and actinides series which fall at the bottom of the comes under the category of inner transition elements.
In these elements the 4f and 5f orbitals are partially filled, rendering them special properties.
In 1869, Dmitri Mendeleev and Lothar Meyer established the periodic law independently.

The first periodic table was developed by Mendeleev and soon followed by Meyer. Each grouped the elements by their mass and proposed regularly reoccurring those properties. Periodic law is recognized as one of chemistry’s most important concepts. While dealing with the chemical elements, their properties, and their chemical reactions, each chemist makes use of Periodic Law, whether consciously or not.

The development of the modern periodic table was driven by periodic law.
Periodic trends are common patterns in the periodic table showing us the various aspects of an element such as electronegativity, atomic radius, or ionizing power.
The periodic law tells us that when grouped by atomic number, certain properties of elements occur periodically.

Generally, nuclear mass decreases from left to right and always increases from top to bottom. As the atomic number has been developed as the basis for organizing the elements on the periodic table, the atomic number will always increase from left to right and top to bottom.

In a given period, the valence shell electronic configuration of any two elements is not the same. Because of this, elements throughout time have different chemical properties with a periodic gradation from left to right for their physical properties. This is referred to as periodic property. This is just a brief description of the periodic table and the classification of elements.

To know more about it, register with BYJU’S & download BYJU’S – the learning app. If you still have doubts regarding the periodic law and would like to learn about periodic table class 10, check out our for detailed clarification. Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin! Select the correct answer and click on the “Finish” buttonCheck your score and answers at the end of the quiz Visit BYJU’S for all Chemistry related queries and study materials

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View Quiz Answers and Analysis : Modern Periodic Law with Detailed Periodic Classification Of Elements

What is the main idea in the periodic law?

The Periodic Law states that the physical and chemical properties of the elements recur in a systematic and predictable way when the elements are arranged in order of increasing atomic number, Many of the properties recur at intervals. When the elements are arranged correctly, the trends in element properties become apparent and can be used to make predictions about unknown or unfamiliar elements, simply based on their placement on the table.

How was the periodic law discovered?

The periodic table of elements is a common sight in classrooms, campus hallways and libraries, but it is more than a tabular organization of pure substances. Scientists can use the table to analyze reactivity among elements, predict chemical reactions, understand trends in periodic properties among different elements and speculate on the properties of those yet to be discovered. Wikimedia Among the scientists who worked to created a table of the elements were, from left, Antoine Lavoisier, Johann Wolfang Döbereiner, John Newlands and Henry Moseley. In 1789, French chemist Antoine Lavoisier tried grouping the elements as metals and nonmetals.

Forty years later, German physicist Johann Wolfang Döbereiner observed similarities in physical and chemical properties of certain elements. He arranged them in groups of three in increasing order of atomic weight and called them triads, observing that some properties of the middle element, such as atomic weight and density, approximated the average value of these properties in the other two in each triad.

A breakthrough came with the publication of a revised list of elements and their atomic masses at the first international conference of chemistry in Karlsruhe, Germany, in 1860. They concluded that hydrogen would be assigned the atomic weight of 1 and the atomic weight of other elements would be decided by comparison with hydrogen. Dmitri Mendeleev Lothar Meyer British chemist John Newlands was the first to arrange the elements into a periodic table with increasing order of atomic masses. He found that every eight elements had similar properties and called this the law of octaves. He arranged the elements in eight groups but left no gaps for undiscovered elements.

In 1869, Russian chemist Dmitri Mendeleev created the framework that became the modern periodic table, leaving gaps for elements that were yet to be discovered. While arranging the elements according to their atomic weight, if he found that they did not fit into the group he would rearrange them. Mendeleev predicted the properties of some undiscovered elements and gave them names such as “eka-aluminium” for an element with properties similar to aluminium.

Later eka-aluminium was discovered as gallium. Some discrepancies remained; the position of certain elements, such as iodine and tellurium, could not be explained. German chemist Lothar Meyer produced a version of the periodic table similar to Mendeleev’s in 1870.

He left gaps for undiscovered elements but never predicted their properties.
The Royal Society of London awarded the Davy Medal in 1882 to both Mendeleev and Meyer.
The later discovery of elements predicted by Mendeleev, including gallium (1875), scandium (1879) and germanium (1886), verified his predictions and his periodic table won universal recognition.

In 1955 the 101st element was named mendelevium in his honor. Wikimedia The 1869 periodic table by Mendeleev in Russian, with a title that translates “An experiment on a system of elements, based on their atomic weights and chemical similarities.”, The concept of sub-atomic particles did not exist in the 19 th century.

In 1913, English physicist Henry Moseley used X-rays to measure the wavelengths of elements and correlated these measurements to their atomic numbers.
He then rearranged the elements in the periodic table on the basis of atomic numbers.
This helped explain disparities in earlier versions that had used atomic masses.

In the periodic table, the horizontal rows are called periods, with metals in the extreme left and nonmetals on the right. The vertical columns, called groups, consist of elements with similar chemical properties. The periodic table provides information about the atomic structure of the elements and the chemical similarities or dissimilarities between them.

Scientists use the table to study chemicals and design experiments. It is used to develop chemicals used in the pharmaceutical and cosmetics industries and batteries used in technological devices. UNESCO named 2019 the International Year of the Periodic Table to mark the 150 th anniversary of Mendeleev’s publication.

Researchers and teachers worldwide took this opportunity to reflect on the importance of the periodic table and spread awareness about it in classrooms and beyond. Workshops and conferences encouraged people to use the knowledge of the periodic table to solve problems in health, technology, agriculture, environment and education.

Is the periodic table a law or theory?

Electron configuration – The periodic table is a graphic description of the periodic law, which states that the properties and atomic structures of the chemical elements are a periodic function of their atomic number, Elements are placed in the periodic table by their electron configurations, which exhibit periodic recurrences that explain the trends of properties across the periodic table.

An electron can be thought of as inhabiting an atomic orbital, which characterises the probability it can be found in any particular region of the atom. Their energies are quantised, which is to say that they can only take discrete values. Furthermore, electrons obey the Pauli exclusion principle : different electrons must always be in different states.

This allows classification of the possible states an electron can take in various energy levels known as shells, divided into individual subshells, which each contain one or more orbitals. Each orbital can contain up to two electrons: they are distinguished by a quantity known as spin, conventionally labeled “up” or “down”.

In a cold atom (one in its ground state), electrons arrange themselves in such a way that the total energy they have is minimised by occupying the lowest-energy orbitals available.
Only the outermost electrons (so-called valence electrons ) have enough energy to break free of the nucleus and participate in chemical reactions with other atoms.

The others are called core electrons,

ℓ → n ↓	0	1	2	3	4	5	6
Orbital	s	p	d	f	g	h	i	Capacity of shell (2 n 2 )
1	1s							2
2	2s	2p						8
3	3s	3p	3d					18
4	4s	4p	4d	4f				32
5	5s	5p	5d	5f	5g			50
6	6s	6p	6d	6f	6g	6h		72
7	7s	7p	7d	7f	7g	7h	7i	98
Capacity of subshell	2	6	10	14	18	22	26

Elements are known with up to the first seven shells occupied. The first shell contains only one orbital, a spherical s orbital. As it is in the first shell, this is called the 1s orbital. This can hold up to two electrons. The second shell similarly contains a 2s orbital, and it also contains three dumbbell-shaped 2p orbitals, and can thus fill up to eight electrons (2×1 + 2×3 = 8).

The third shell contains one 3s orbital, three 3p orbitals, and five 3d orbitals, and thus has a capacity of 2×1 + 2×3 + 2×5 = 18. The fourth shell contains one 4s orbital, three 4p orbitals, five 4d orbitals, and seven 4f orbitals, thus leading to a capacity of 2×1 + 2×3 + 2×5 + 2×7 = 32. Higher shells contain more types of orbitals that continue the pattern, but such types of orbitals are not filled in the ground states of known elements.

The subshell types are characterised by the quantum numbers, Four numbers describe an orbital in an atom completely: the principal quantum number n, the azimuthal quantum number ℓ (the orbital type), the magnetic quantum number m ℓ, and the spin quantum number s,

What is the theory of Mendeleev periodic table?

Read a brief summary of this topic – Dmitri Mendeleev, Russian in full Dmitry Ivanovich Mendeleyev, (born January 27 (February 8, New Style), 1834, Tobolsk, Siberia, Russian Empire—died January 20 (February 2), 1907, St. Petersburg, Russia), Russian chemist who developed the periodic classification of the elements.

Mendeleev found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements. In his version of the periodic table of 1871, he left gaps in places where he believed unknown elements would find their place.

He even predicted the likely properties of three of the potential elements. The subsequent proof of many of his predictions within his lifetime brought fame to Mendeleev as the founder of the periodic law,

Why was Mendeleev’s periodic law modified?

Demerits of Mendeleev Periodic Table –

He was unable to locate hydrogen in the periodic table. Increase in atomic mass was not regular while moving from one element to another. Hence, the number of elements yet to be discovered was not predictable. Later on, were found which violated Mendeleev’s periodic law.

Also, Read ⇒ Mendeleev claimed the famous periodic law that “Element properties are a periodic function of their atomic weight.” Mendeleev placed elements in the order of their atomic weights in the form of a table known as the Periodic Table of Mendeleev.

The main differences are: the periodic table of Mendeleev is based on atomic mass.
The current periodic table is based on the number of atoms.
Noble gasses (as they are not found at that time) were not included in Mendeleev’s periodic table.
In Modern periodic table noble gases are in a separate group called group-18.

Mendeleev was not himself estimating the atomic mass. He had the information he was working on to see the repeated properties to find a pattern that turned out to be a chart. He predicted their atomic mass on the basis of the pattern he observed for the atoms that were not detected.

Mendeleyev is best known for his discovery of the periodic law he adopted in 1869 and the periodic table of elements he developed. He died on February 2, 1907, in St. Petersburg, Russia. A series of simple rules will determine the number of protons, neutrons and electrons in an atom. The hydrogen nucleus number of protons is equal to the atomic number (Z).

In a neutral atom, the number of electrons is equal to the number of protons. To know more about Mendeleev’s work and Mendeleev periodic table, demerits and merits of Mendeleev’s periodic table in detail, you can read the Mendeleev periodic table PDF. Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin! Select the correct answer and click on the “Finish” buttonCheck your score and answers at the end of the quiz Visit BYJU’S for all Chemistry related queries and study materials

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View Quiz Answers and Analysis : Mendeleev Periodic Table PDF consists of Introduction, Properties, Merits & Demerits

What is the cause of periodicity?

The cause of periodicity of properties of elements is due to the repetition of similar electronic configuration of their atoms in the outermost energy shell after certain regular interval.

What is the law of periodicity?

: a law in chemistry: the elements when arranged in the order of their atomic numbers show a periodic variation of atomic structure and of most of their properties

What was the original form of the periodic law?

The United Nations declared 2019 to be the International Year of the Periodic Table, celebrating the 150th anniversary of the discovery of the periodic law. Early in 1869, Russian chemist Dmitri Mendeleev was in a predicament many people are familiar with—he was facing a deadline.

He had delivered the first volume of his inorganic chemistry textbook to his publisher but was struggling with how to organize the second volume.
This struggle would culminate in a remarkable discovery, a system that classified all of the chemical elements.
In March 1869, Mendeleev delivered a full paper to the Russian Chemical Society spelling out the most significant aspect of his system, that characteristics of the elements recur at a periodic interval as a function of their atomic weight.

This was the first iteration of the periodic law. Russian chemist and educator Dmitrii Mendeleev is best known today for his creation of the periodic table of elements. Mendeleev was far from the first chemist to attempt to organize the elements by atomic weight or to recognize that characteristics recurred on some sort of regular basis.

Through much of the nineteenth century, chemists had worked to find an organizing principle that encompassed all of the known elements and that could be considered a law of nature.
Mendeleev’s system was not perfect but it had the hallmarks of a scientific law, one that would hold true through new discoveries and against all challenges.

One of the unique aspects of Mendeleev’s table was the gaps he left. In these places he not only predicted there were as-yet-undiscovered elements, but he predicted their atomic weights and their characteristics. The discovery of new elements in the 1870s that fulfilled several of his predictions brought increased interest to the periodic system and it became not only an object of study but a tool for research. Sir William Ramsay, who, in the 1890s, discovered the existence of the noble gases, a previously unpredicted set of elements. In the 1890s, William Ramsay discovered an entirely new and unpredicted set of elements, the noble gases. After uncovering the first two, argon and helium, he quickly discovered three more elements after using the periodic system to predict their atomic weights.

The noble gases had unusual characteristics—they were largely inert and resistant to combining with other substances—but the entire set fit easily into the system.
The discovery of radioactivity in 1896 seemed poised to destroy the periodic system.
Chemists had always considered elements to be substances that could not break down into smaller parts.

How could radioactive elements, which decayed into other substances, be considered elements? And if they were, how could so many fit into the very few gaps left in the table? Chemists and physicists working together began to understand the structure of the atom and were soon able to explain how the periodic system worked on an atomic level. The 1896 discovery of radioactivity created significant problems for the periodic system. Rather than atomic weight, atomic number—the number of protons in the nucleus of an atom—determined the characteristics of an element. Rather miraculously, organizing the elements by their atomic number rather than their atomic weight did not change the arrangement of the periodic table.

In fact, understanding how electrons fill the shells orbiting a nucleus explained some of the anomalies that had plagued the periodic system from the start.
The periodic table—the visual representation of the periodic law—is recognized as one of the great achievements of chemistry and as a uniting scientific concept, relevant to the physical and life sciences alike.

But the periodic table is also an important aspect of science education. It took time for the periodic table of elements to develop into its current form, and many of its early iterations – such as this one, called ” Mendeleev’s Flower ” – would be unrecognizable today. Mendeleev and many of the others who developed systems to organize the elements did so in their roles as chemical educators rather than as chemical researchers.

He was writing a textbook for his students at St.
Petersburg University (the only available chemistry textbooks in Russian were translations) when he developed his periodic law.
Perhaps most important, he continued to draw revised versions of the periodic table throughout his life.
Neither Mendeleev’s first attempt at the periodic system nor his most popular table from 1870 look much like the periodic table that hangs today on the wall of most chemistry classrooms or appears inside the cover of most chemistry textbooks.

Now, there are probably 1,000 different periodic tables of the elements. Mendeleev’s early periodic system – shown here in its 1871 form – looked much different from the modern periodic table known to today’s chemistry students. The majority of these tables look fantastical in comparison with the castle-like table that is found in classrooms.

Curved forms such as spirals, helices, and three-dimensional figures-of-eight were wildly popular amongst educators well into the twentieth century. These were generally deemed to be easier for students to use to learn about the elements and the relationships between them than a flat, two-dimensional table.

The thing about a flat, two-dimensional table, however, is that if fits easily onto one page or as a poster hanging on the wall. It doesn’t require special fold-outs or printing techniques. It can easily be shrunk or expanded to fit as needed within a text. A photograph of the Wilson College chemistry club in Chambersburg, PA circa 1937 shows an example of the Van Nostrand Company periodic table visible in the background (photo courtesy of ScienceHistory.org.) So why this one table? Where did it come from? There were so many similar tables that in some ways it just evolved over time. A 1923 Deming Periodic Table ; chemists frequently credit Horace Deming, a professor at the University of Nebraska, with being the progenitor of the modern periodic table. Chemical educators lauded Deming’s table, but scientific supply companies made it famous.

Merck handed it out as part of a promotional campaign in the 1920s.
The Welch Scientific Company sold it in the form of wall charts, and in standard page size and vest pocket editions.
Eventually it was included in standard reference handbooks such as the CRC Handbook of Chemistry and Physics and Lange’s Handbook of Chemistry,

By the 1950s, versions of Deming’s table could be found in a majority of chemistry textbooks. Today, renderings of the table can be found on almost any type of consumer good—shower curtains, coffee mugs, key chains, phone covers, and the list goes on, The modern periodic table of elements : known, loved, and feared by chemistry students today. The story of the periodic table is in many ways one about textbooks, things that are usually given short shrift. But consider that Mendeleev made his name in the Russian chemical community by writing a textbook (his organic chemistry textbook won a prize), and then became famous by discovering a law while in the process of writing another textbook.

What observation led to the development of the modern periodic law?

Chapter: 11th 12th std standard Class Organic Inorganic Physical Chemistry Higher secondary school College Notes – What Theory Explains The Underlying Reasons For The Periodic Law In 1913, a British Physicist Henry Moseley showed that the atomic number is a more fundamental property of an element than its atomic weight. This observation led to the development of modern periodic law. Modern Periodic Law In 1913, a British Physicist Henry Moseley showed that the atomic number is a more fundamental property of an element than its atomic weight.

This observation led to the development of modern periodic law.
The modern periodic law states that ‘ the physical and chemical properties of the elements are periodic function of their atomic numbers.’ This means that when the elements are arranged in order of increasing atomic numbers, the elements with similar properties recur after regular intervals.

The periodic repetition is called periodicity. The physical and chemical properties of the elements are related to the arrangement of electrons in the outermost shell. Thus, if the arrangement of electrons in the outermost shell (valence shell) of the atoms is the same, their properties will also be similar.

For example, the valence shell configurations of alkali metals show the presence of one electron in the s-orbital of their valence shells. Similar behaviour of alkali metals is attributed to the similar valence shell configuration of their atoms. Similarly, if we examine the electronic configurations of other elements, we will find that there is repetition of the similar valence shell configuration after certain regular intervals with the gradual increase of atomic number.

Thus we find that the periodic repetition of properties is due to the recurrence of similar valence shell configuration after certain intervals. It is observed that similarity in properties is repeated after the intervals of 2, 8, 18, or 32 in their atomic numbers.

Long form of the Periodic Table: The periodic table is constructed on the basis of repeating electronic configurations of the atoms when they are arranged in the order of increasing atomic numbers.
The long form of the Periodic table is given in a modified form in page number 70.
Readers are advised to follow the periodic table closely while studying the structural features of the long form of the Periodic Table.

Structural Features of the Long form of the periodic Table: The long form of the periodic table consists of horizontal rows called periods and vertical columns called groups. Periods: In terms of electronic structure of the atom, a period constitutes a series of elements whose atoms have the same number of electron shell i.e., principal quantum number (n).

There are seven periods and each period starts with a different principal quantum number. The first period corresponds to the filling of electrons in the first energy shell (n = 1). Now this energy level has only one orbital (1s) and, therefore, it can accommodate two electrons. This means that there can be only two elements (hydrogen, 1s 1 and helium, 1s 2 ) in the first period.

The second period starts with the electron beginning to enter the second energy shell (n = 2). Since there are only four orbitals (one 2s-and three 2p- orbitals) to be filled, it can accommodate eight electrons. Thus, second period has eight elements in it.

It starts with lithium (Z = 3) in which one electron enters the 2s-orbital. The period ends with neon (Z = 10) in which the second shell is complete (2s 2 2p 6 ). The third period begins with the electrons entering the third energy shell (n = 3). It should be noted that out of nine orbitals of this energy level (one s, three p and five d) the five 3d-orbitals have higher energy than 4s-orbitals.

As such only four orbitals (one 3s and three 3p) corresponding to n = 3 are filled before fourth energy level begins to be filled. Hence, third period contains only eight elements from sodium (Z = 11) to argon (Z = 18). The fourth period corresponding to n = 4 involves the filling of one 4s and three 4p-orbitals (4d and 4f orbitals have higher energy than 5s-orbital and are filled later).

In between 4s and 4p-orbitals, five 3d-orbitals are also filled which have energies in between these orbitals. Thus, altogether nine orbitals (one 4s, five 3d and three 4p ) are to be filled and therefore, there are eighteen elements in fourth period from potassium (Z = 19) to krypton (Z = 36). The elements from scandium (Z = 21) to zinc (Z = 30) are called 3d- transition series.

The fifth period beginning with 5s-orbital (n=5) is similar to fourth period. There are nine orbitals (one 5s, five 4d and three 5p) to be filled and, therefore, there are eighteen elements in fifth period from rubidium (Z = 37) to xenon (Z = 54). The sixth period starts with the filling of 6s-orbitals (n= 6).

There are sixteen orbitals (one 6s, seven 4f, five 5d, and three 6p) in which filling of electrons takes place before the next energy level starts.
As such there are thirty two elements in sixth period starting from cesium (Z = 55) and ending with radon (Z = 86).
The filling up of 4f orbitals begins with cerium (Z = 58) and ends at lutetium (Z = 71).

It constitutes the first f-inner transition series which is called lanthanide series. The seventh period begins with 7s-orbital (n = 7). It would also have contained 32 elements corresponding to the filling of sixteen orbitals (one 7s, seven 5f, five 6d and three 7p), but it is still incomplete.

At present there are 23 elements in it. The filling up of 5f- orbitals begins with thorium (Z = 90) and ends up at lawrencium (Z = 103). It constitutes second f-inner transition series which is called actinide series. It mostly includes man made radioactive elements. In order to avoid undue extension of the periodic table the 4f and 5f- inner transition elements are placed separately.

The number of elements and the corresponding orbitals being filled are given below. Principal Orbitals Electrons to Number of Period Valence being filled be accommo- shell (=n) up dated electrons First N = 1 1s 2 2 Second N = 2 2s, 2p 2+6 8 Third n = 3 3s, 3p 2+6 8 Fourth n = 4 4s, 3d, 4p 2 +10+6 18 Fifth n = 5 5s, 4d, 5p 2+10+6 18 Sixth n = 6 6s, 4f, 5d, 6p 2+14+10+6 32 Seventh n = 7 7s, 5f, 6d, 7p 2+14+10+6 32 What Theory Explains The Underlying Reasons For The Periodic Law The first three periods containing 2, 8 and 8 elements respectively are called short periods, the next three periods containing 18, 18 and 32 elements respectively are called long periods. Groups A vertical column in the periodic table is known as group.

A group consists of a series of elements having similar configuration of the outer energy shell.
There are eighteen vertical columns in long from of the periodic table.
According to the recommendations of the International Union of Pure and Applied Chemistry (IUPAC), these groups are numbered from 1 to 18.

Previously, these were numbered from I to VII as A and B, VIII and zero groups elements. The elements belonging to the same group are said to constitute a family. For example, elements of group 17 (VII A) constitute halogen family. Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail 11th 12th std standard Class Organic Inorganic Physical Chemistry Higher secondary school College Notes : Modern Periodic Law |

Who discovered periodic law and when was it discovered?

Comprehensive formalizations – Properties of the elements, and thus properties of light and heavy bodies formed by them, are in a periodic dependence on their atomic weight. — Russian chemist Dmitri Mendeleev, formulating the periodic law for the first time in his 1871 article “Periodic regularity of the chemical elements” French geologist Alexandre-Émile Béguyer de Chancourtois noticed that the elements, when ordered by their atomic weights, displayed similar properties at regular intervals.

In 1862, he devised a three-dimensional chart, named the “telluric helix”, after the element tellurium, which fell near the center of his diagram. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois saw that elements with similar properties lined up vertically.

The original paper from Chancourtois in Comptes rendus de l’Académie des Sciences did not include a chart and used geological rather than chemical terms. In 1863, he extended his work by including a chart and adding ions and compounds, The next attempt was made in 1864.

British chemist John Newlands presented a classification of the 62 known elements. Newlands noticed recurring trends in physical properties of the elements at recurring intervals of multiples of eight in order of mass number; based on this observation, he produced a classification of these elements into eight groups.

Each group displayed a similar progression; Newlands likened these progressions to the progression of notes within a musical scale. Newlands’s table left no gaps for possible future elements, and in some cases had two elements at the same position in the same octave.

Newlands’s table was ridiculed by some of his contemporaries.
The Chemical Society refused to publish his work.
The president of the Society, William Odling, defended the Society’s decision by saying that such ‘theoretical’ topics might be controversial; there was even harsher opposition from within the Society, suggesting the elements could have been just as well listed alphabetically.

Later that year, Odling suggested a table of his own but failed to get recognition following his role in opposing Newlands’s table. German chemist Lothar Meyer also noted the sequences of similar chemical and physical properties repeated at periodic intervals.

According to him, if the atomic weights were plotted as ordinates (i.e.
Vertically) and the atomic volumes as abscissas (i.e.
Horizontally)—the curve obtained is a series of maximums and minimums—the most electropositive elements would appear at the peaks of the curve in the order of their atomic weights.

In 1864, a book of his was published; it contained an early version of the periodic table containing 28 elements, and classified elements into six families by their valence —for the first time, elements had been grouped according to their valence. Works on organizing the elements by atomic weight had until then been stymied by inaccurate measurements of the atomic weights.

In 1868, he revised his table, but this revision was published as a draft only after his death.
In a paper dated December 1869 which appeared early in 1870, Meyer published a new periodic table of 55 elements, in which the series of periods are ended by an element of the alkaline earth metal group.
The paper also included a line chart of relative atomic volumes, which illustrated periodic relationships of physical characteristics of the elements, and which assisted Meyer in deciding where elements should appear in his periodic table.

By this time he had already seen the publication of Mendeleev’s first periodic table, but his work appears to have been largely independent. In 1869, Russian chemist Dmitri Mendeleev arranged 63 elements by increasing atomic weight in several columns, noting recurring chemical properties across them.

It is sometimes said that he played “chemical solitaire” on long train journeys, using cards with the symbols and the atomic weights of the known elements.
Another possibility is that he was inspired in part by the periodicity of the Sanskrit alphabet, which was pointed out to him by his friend and linguist Otto von Böhtlingk,

Mendeleev used the trends he saw to suggest that atomic weights of some elements were incorrect, and accordingly changed their placements: for instance, he figured there was no place for a trivalent beryllium with the atomic weight of 14 in his work, and he cut both the atomic weight and valency of beryllium by a third, suggesting it was a divalent element with the atomic weight of 9.4.

Mendeleev widely distributed printed broadsheets of the table to various chemists in Russia and abroad. Mendeleev argued in 1869 there were seven types of highest oxides. Mendeleev continued to improve his ordering; in 1870, it gained a tabular shape, and each column was given its own highest oxide, and in 1871, he further developed it and formulated what he termed the “law of periodicity”.

Some changes also occurred with new revisions, with some elements changing positions.

Various attempts to construct a comprehensive formalization
Meyer’s periodic table, published in “Die modernen Theorien der Chemie”, 1864
Newlands’s law of octaves, 1866
Mendeleev’s first Attempt at a system of elements, 1869
Mendeleev’s Natural system of the elements, 1870
Mendeleev’s periodic table, 1871

Is Mendeleev’s periodic law?

Mendeleev’s periodic law states that ‘ The properties are a periodic function of their atomic mass.’ This means that the chemical and physical properties of the elements recur periodically when the elements are arranged in the order of their atomic weights.

Did Charles Darwin create the periodic table?

The periodic table of elements – Mendeleev’s great discovery of the periodic table was presented to the world in 1869 at a meeting of the recently formed Russian Chemical Society. Like Darwin, Mendeleev also wrote a very influential book, The Principles of Chemistry, which helped to propagate his ideas further afield.

As in the case of most scientific discoveries, many other scientists—such as De Chancourtois, Newlands, and Lothar Meyer—had arrived at earlier precursors to the periodic table of the elements but none of them achieved the kind of lasting success that Mendeleev did.
This fact is generally believed to be due to a number of successful predictions that Mendeleev made about the existence of new elements that were eventually discovered and that had almost exactly the properties that Mendeleev had foreseen.

Even in his first published table of 1869, Mendeleev clearly predicted the existence of three new elements, which he stated would have atomic weights of 44, 68, and 72, respectively. Within a period of 15 years all three of these elements—subsequently named gallium, germanium, and scandium—were indeed discovered and found to have atomic weights of 44, 69.2, and 72.3.

What was the original form of the periodic law?

He had delivered the first volume of his inorganic chemistry textbook to his publisher but was struggling with how to organize the second volume.
This struggle would culminate in a remarkable discovery, a system that classified all of the chemical elements.
In March 1869, Mendeleev delivered a full paper to the Russian Chemical Society spelling out the most significant aspect of his system, that characteristics of the elements recur at a periodic interval as a function of their atomic weight.

Through much of the nineteenth century, chemists had worked to find an organizing principle that encompassed all of the known elements and that could be considered a law of nature. Mendeleev’s system was not perfect but it had the hallmarks of a scientific law, one that would hold true through new discoveries and against all challenges.

The noble gases had unusual characteristics—they were largely inert and resistant to combining with other substances—but the entire set fit easily into the system. The discovery of radioactivity in 1896 seemed poised to destroy the periodic system. Chemists had always considered elements to be substances that could not break down into smaller parts.

In fact, understanding how electrons fill the shells orbiting a nucleus explained some of the anomalies that had plagued the periodic system from the start. The periodic table—the visual representation of the periodic law—is recognized as one of the great achievements of chemistry and as a uniting scientific concept, relevant to the physical and life sciences alike.

He was writing a textbook for his students at St. Petersburg University (the only available chemistry textbooks in Russian were translations) when he developed his periodic law. Perhaps most important, he continued to draw revised versions of the periodic table throughout his life. Neither Mendeleev’s first attempt at the periodic system nor his most popular table from 1870 look much like the periodic table that hangs today on the wall of most chemistry classrooms or appears inside the cover of most chemistry textbooks.

Curved forms such as spirals, helices, and three-dimensional figures-of-eight were wildly popular amongst educators well into the twentieth century. These were generally deemed to be easier for students to use to learn about the elements and the relationships between them than a flat, two-dimensional table.

Merck handed it out as part of a promotional campaign in the 1920s. The Welch Scientific Company sold it in the form of wall charts, and in standard page size and vest pocket editions. Eventually it was included in standard reference handbooks such as the CRC Handbook of Chemistry and Physics and Lange’s Handbook of Chemistry,

On which law the modern periodic table is based?

Free 10 Questions 10 Marks 6 Mins The correct answer is Moseley, Concept:

The modern periodic law is the basis and principle on which the periodic table is set up. A periodic table is an arrangement of elements based on their atomic numbers and chemical properties,

Explanation: In 1913, Henry Moseley showed that the atomic number (symbolised as Z) of an element is a more fundamental property than its atomic mass. Accordingly, Mendeléev’s Periodic Law was modified and the atomic number was adopted as the basis of Modern Periodic Table and the Modern Periodic Law can be stated as follows: ‘Properties of elements are a periodic function of their atomic number.’ The periodic law was developed independently by Dmitri Mendeleev and Lothar Meyer in 1869.

Mendeleev created the first periodic table and was shortly followed by Meyer. They both arranged the elements by their mass and proposed that certain properties periodically reoccur. In 1869, Dmitri Mendeleev and Lothar Meyer individually came up with their own periodic law “when the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically.” Meyer based his laws on the atomic volume (the atomic mass of an element divided by the density of its solid form), this property is called Molar volume.

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What is Mendeleev’s periodic law?

Mendeleev’s periodic law states that the physical and chemical properties of elements are a periodic function of their atomic weights.

How are elements arranged based on periodic law?

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The periodic table, also called the periodic table of elements, is an organized arrangement of the 118 known chemical elements. The chemical elements are arranged from left to right and top to bottom in order of increasing atomic number, or the number of protons in an atom ‘s nucleus, which generally coincides with increasing atomic mass.

The horizontal rows on the periodic table are called periods, where each period number indicates the number of orbitals for the elements in that row, according to Los Alamos National Laboratory (opens in new tab),
Atoms have protons and neutrons in their nucleus, and surrounding that, they have their electrons arranged in orbitals, where an atomic orbital is a math term that describes the location of an electron as well as its wave-like behavior.) For instance, period 1 includes elements that have one atomic orbital where electrons spin; period 2 has two atomic orbitals, period 3 has three and so on up to period 7.

The columns, or groups, on the periodic table represent the atomic elements that have the same number of valence electrons, or those electrons in the outermost orbital shell. As an example, elements in Group 8A (or VIIIA) all have a full set of eight electrons in the highest-energy orbital, according to chemist William Reusch, on his webpage at Michigan State University (opens in new tab),