Modern Periodic Table And Its Significance

History of the Periodic Table

Earlier scientists assumed that the properties of elements are periodic functions of their atomic masses. On the basis of this assumption, Mendeleev placed 63 elements in a vertical column called groups and in horizontal rows called periods. This method was rejected as it could not explain the position of certain elements, rare earth metals, and isotopes. A scientist named Henry Moseley removed these defects and put forward the modern periodic table with the modern periodic law.

Moseleys Periodic law:

He stated that the properties of elements are periodic functions of their atomic number.

Modern Periodic Table:

A tabular arrangement of elements in groups and periods which highlights the regular trends in properties of elements is defined as the periodic table.

modern periodic table

Features of Modern Periodic Table

There are eighteen vertical columns known as groups in the modern periodic table which are arranged from left to right and seven horizontal rows which are known as periods.

Group number

Group name

Property

Group 1 or IA

Alkali metals

They form strong alkalis with water

Group 2 or IIA

Alkaline earth metals

They also form alkalis but weaker than group 1 elements

Group 13 or IIIA

Boron family

Boron is the first member of this family

Group 14 or IVA

Carbon family

Carbon is the first member of this property

Group 15 or VA

Nitrogen family

This group has non-metals and metalloids

Group 16 or VIA

Oxygen family

They are also known as chalcogens

Group 17 or VIIA

Halogen family

The elements of this group form salts.

Group 18

Zero group

They are noble gases and under normal conditions they are inert.

Classifications Of Elements in the periodic table

The elements of group 1, 2, 13, 14, 15, 16, and 17 are known as the main group elements or normal elements. The elements of groups 3, 4, 5, 6, 7, 8, 9, 11 and 12 are known as the transition elements. The group 18 is called the noble gases or inert gases. Their outermost shell is completely filled. Due to this stable electronic configuration, they generally don’t react with the other elements.

When we talk about the periods of a modern periodic table, one should keep in mind that the number of shells present in an atom determines its period number. The elements of period one will have only one shell, elements of period two will have two shells and so on. The first period of the modern periodic table is the shortest period as it contains only two elements. The period number two and three consists of eight elements each and is known as short groups. The period four and five have eighteen elements and are known as the long group. In the modern periodic table, the group number 3 of period six contains the lanthanide series which are the rare earth elements. We have radioactive elements (actinides) present in group 3 of period seven.

So we have seen the properties of the modern periodic table. To learn more about the periodic table and other concepts of chemistry, register with BYJU’S.

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Practise This Question

Identify the gases that are chemically inert.