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Modern Periodic Law

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All matter in our environment is made up of basic units known as elements. Initially, only 31 chemical elements were discovered in 1800 and it was easier to study their chemical and other properties. However, as more and more elements were discovered due to technological advancements in science, it became harder to study all the elements simultaneously. Scientists began to think about a method to simplify the study of elements in order to make their work easier.

It was observed that elements’ properties have periodicity, and to study the properties of elements in a fixed pattern, many tables were created to arrange the elements in an ordered manner based on their characteristics. Some examples of these are Doberiener’s triads, Newland’s octaves, Mendeleev’s periodic table, etc.

Significance of the Periodic Classification of Elements

  • The classification of elements into groups provides us with a fixed pattern in which the elements’ properties change on a regular basis. The periodic table simplified and organized the study of elements’ physical and chemical properties. We can now simply go to the group and see the properties of the periodic table elements or predict the properties of an element if we know the properties of other elements in the same group.
  • Despite the fact that so many elements have already been discovered, there is still a chance that new elements will be discovered. Scientists can use a periodic table to learn about the trending characteristics of elements based on their properties, and thus distinguish new elements from existing ones. Furthermore, researchers are constantly striving to discover new elements and investigate their properties.

What is Modern Periodic Law?

Dmitri Mendeleev, a Russian chemist, observed a pattern among the elements: as their atomic masses increased, their chemical and physical properties repeated with prior elements. He named this property Mendeleev’s Periodic Law. However, this law was not accurate for all elements, as only 63 were known at the time.

In an effort to improve upon Mendeleev’s Periodic Law, Henry Moseley proposed the Modern Periodic Law, which states that 

“The physical and chemical properties of the elements are periodic functions of their atomic numbers.” 

The atomic number is considered the number of protons or electrons in a neutral element. Through extensive advancements and research in the field of science, we now have a wealth of knowledge about atoms, their behaviours, and their properties. With this knowledge, scientists can now classify and pair elements with similar properties with ease that Mendeleev could never have imagined. These advancements have resulted in the form of the Modern Periodic Table.

Moseley Law

Modern periodic law is sometimes also called Moseley Law as it was given by Henry Moseley hence the name Moseley law, which states that,

“Various properties of the chemical elements whether Physical or Chemical are periodic functions of its  atomic mass.”

Mendeleev Periodic Table

Dimitri Mendeleev arranged all the known elements to him in the order of increasing atomic mass and saw the periodic pattern in their properties. As there were only 63 elements known to Mendeleev and some of the smaller nucleus atoms are also not discovered yet, he left some gaps in the table so that the other elements can be collected with their similar property elements. Mendeleev’s version of the periodic table is as follows:

Mendeleev Periodic Table

 

Modern Periodic Table

The Modern Periodic Table, also known as the long form of the Periodic Table, is a continuation of Mendeleev’s work. However, in the Modern Periodic Table, Neil Bohr used the atomic number of elements as the basis for periodicity. Bohr divided all the elements into 18 groups, labelled 1 to 18, and 7 periods, named 1 to 7. The groups are made up of elements that have atoms with similar outer shell electronic configurations, while the periods are made up of elements with the same number of shells in total.

Modern Periodic Table

 

Classification of the Elements in the Modern Periodic Table

We classify elements in the periodic table in rows, columns, and blocks that are discussed below,

In Peiods and Groups

Elements are classified into 7 periods and 18 groups where elements in each group are placed using the electrons in their outermost shell and elements in each period are placed using the number of shells of each element.

The number of elements in each period:

  • First period has 2 elements.
  • Second period has 8 elements.
  • Third period has 8 elements.
  • Fourth period has 18 elements.
  • Ffifth period has 18 elements.
  • Sixth period has 32 elements.
  • Seventh period has the rest of the elements.

In Blocks

The Modern Periodic Table is divided into four blocks that are as follows:

  • s-Block
  • p-Block
  • d-Block
  • f-Block

Now let’s learn about each block in brief.

s-Block Elements

Groups 1 and 2 are included in the s-Block as elements these blocks have their valence electron in the s-orbital. Also, these groups are also called alkali and alkali-earth metals respectively and their electronic configuration is ns1 and ns2 for group 1 and group 2 elements, where n is the period of that element.

p-Block Elements

Group 13 to Group 18 are included in the p-Block as elements in these blocks have their electronic configuration like ns2np1-6. Some of the most useful elements to mankind are found in this block such as Carbon, Silicon, Aluminium, Phosphorus, Sulfur, etc.

Learn more about, p-block

d-Block Elements

All the elements from group 3 to group 12 are collectively called d-Block elements. These elements are also called transition elements or transition metals as these elements show unstable transitional behaviour between s and p block elements.

f-Block Elements

Only Lanthanide and Actinide series are part of the f-Block. These are called inner transition elements and mark their presence between the elements lanthanum and hafnium and between actinium and rutherfordium. 

Read More,

FAQs on Modern Periodic Law

Q1: State Modern Periodic Law.

Answer:

“The physical and chemical properties of the elements are periodic functions of their atomic numbers.”

Q2: What is the difference between Mendeleev’s Periodic Law and Modern Periodic Law?

Answer.

In Mendeleev’s  period law atomic mass is considered as base for periodicity property but in modern periodic law atomic number is considered as the base for the periodicity property.

Q3: Who Gave the Modern Periodic Law?

Answer:

Henry Moseley proposed the modern periodic law in 1913.

Q4: Who invented Modern Periodic Table?

Answer:

Neil Bohr invented the Modern Periodic Table using the Modern Periodic Law.

Q5: How many Periods and Groups are in Modern Periodic Table?

Answer:

There are 18 groups and 7 periods in the Modern Periodic Table.



Last Updated : 19 Dec, 2023
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