Question

An element X which is a yellow solid at room temperature shows catenation and allotropy. X forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are the major air pollutants.

(a) Identify the element X

(b) Write the electronic configuration of X

(c) Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals?

(d) What would be the nature (acidic/ basic) of oxides formed?

(e) Locate the position of the element in the Modern Periodic Table.

Answer 1

(a) Identification of the element X

• Element X is Sulphur (S)

(b) Electronic configuration of the identified element

• Atomic number of Sulphur= 16
• Electronic configuration= $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^4$

(c) Balanced chemical equation for the thermal decomposition of ferrous sulphate crystals

$\underset{(\mathrm{Ferrous}\mathrm{sulphate})}{2{\mathrm{FeSO}}_4\left(\mathrm{s}\right)}\stackrel{\mathrm{Heat}}{\to }\underset{(\mathrm{Ferric}\mathrm{oxide})}{{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)}+\underset{(\mathrm{Sulphur}\mathrm{dioxide})}{{\mathrm{SO}}_2\left(\mathrm{g}\right)}+\underset{(\mathrm{Sulphur}\mathrm{trioxide})}{{\mathrm{SO}}_3\left(\mathrm{g}\right)}$

(d) Nature (acidic/ basic) of oxides formed

Oxides formed are Sulphur dioxide (SO₂) and Sulphur trioxide (SO₃) which are acidic in nature as they furnish an acid on reaction with water.

(e) Position of the element in the Modern Periodic Table

• As last electron entered in the p-subshell, so Sulphur is a p-block element.
• Period is located by identifying the highest value of n (principal quantum number) which is 3 here. So period is 3.
• For the group of a p block element= 12+ number of electrons in p-subshell
• Therefore, group= 12+ 4= 16
• Hence, Sulphur belongs to Period= 4, p- block, group-16 in the modern periodic table.