Question

Oxygen (at. no. 8) and sulphur (at. no. 16) belong to same group of the periodic table.

(a) State the electronic configuration of:

1. Oxygen
2. Sulphur

(b) Name the group in which these elements belong.

Answer 1

(a) Electronic configuration: It is the distribution of electrons in the various shells around the nucleus of an atom.
(i) Atomic number of Oxygen $\left(\mathrm{O}\right)$= 8

• As atomic number= Number of protons and
• Number of protons= Number of electrons for a neutral atom
• Electronic configuration of Silicon= 2, 6 (K, L)

(ii) Atomic number of Sulphur $\left(\mathrm{S}\right)$= 16

• Electronic configuration of Sulphur= 2, 8, 6 (K, L, M)

(b) These elements occur in the group VI A or 16^th group of the modern periodic table.

Group: A group is a vertical column in the periodic table. There are 18 groups in the periodic table.

• The number of valence electrons present in the atom of an element indicate the group number.
• Example: Oxygen and Sulphur both have same number of valence electrons i.e.; 6 valence electrons in their outermost shell i.e. L for Oxygen and M for Sulphur.
• Therefore their group number is VI A. This group is numbered as 16 in the modern periodic table.
• This can also be confirmed from the periodic table given below.