Modern Periodic Classification

Law of Modern Periodic Table states that properties of elements are the periodic function of their atomic numbers. In the modern periodic table, elements are arranged in order of their increasing atomic numbers.

Explanation of Modern Periodic Table:

• Elements are arranged in order of their increasing atomic numbers.
• The vertical columns are known as groups and horizontal columns are known as periods; in the modern periodic table.
• There are 18 groups and 7 periods in the modern periodic table.

Elements having same number of valence electrons are placed in the same group. For example; elements having valence electrons equal to 1 are placed in the 1st group, elements having valence electrons equal to 3 are placed in the 13th group, elements having valence electrons equal to 2 are placed in 2nd group except helium which is placed in 18th group, since it is an inert gas.

Elements having same number of shells are placed in the same period.

Groups in Modern Periodic Table:

1st group: Alkali metals are placed in the 1st group in the modern periodic table. Hydrogen is also placed in the 1st group although hydrogen is not an alkali metal.

2nd group: Alkaline earth metals are placed in the 2nd group in the modern periodic table.

Elements placed in 1st and 2nd groups in the modern periodic table are collectively known as light metals.

3rd to 12th group: Transition elements are placed from 3rd to 12th group in the modern periodic table.

13th group: Metals are placed in the 13th group; except boron which is a metalloid.

14th group: Carbon, silicon, germanium, tin and lead are placed in this group. Among them, carbon is a non-metal, silicon and germanium are metalloids and tin and lead are metals.

15th group: Nitrogen, phosphorous, arsenic, antimony and bismuth are place in the 15th group; among which nitrogen and phosphorous are non-metals, arsenic and antimony are metalloids and bismuth is a metal.

16th group: Oxygen, sulphur, selenium, tellurium and polonium are placed in this group, among which oxygen, sulphur and selenium are non-metals, tellurium is metalloid and polonium is a metal.

17th group: Non-metals are placed in the 17th group. Since, halogens are placed in this group hence this group is also known as group of halogen.

18th group: Noble gases are placed in the 18th group. This group is also known as zero group.

Periods in Modern Periodic Table:

At present there are seven periods in the Modern Periodic Table.

1st period: This is known as very short period as there are only two elements, i.e. hydrogen and helium.

2nd and 3rd period: There are total 8 elements in each of the 2nd and 3rd periods. These periods are known as short periods.

4th and 5th period: There are total 18 elements in each of the 4th and 5th periods. These periods are known as long periods.

6th period: There are total 32 elements in 6th period. This period is known as very long period.

7th period This period is known as incomplete period. Blank spaces in this period are supposed to be filled by the elements discovered in future.