Give reasons for the following:
(a) Lithium atom is smaller than Sodium atom.
(b) Chlorine (Atomic Number 17) is more electronegative than Sulphur (Atomic Number 16).
(a) Electronic configuration of Li is 2,1 and that of Na is 2,8,1. Since sodium has more number of shells, thus a larger size.
(b) E.C. of Cl = 2,8,7
E.C. of S = 2,8,6.
As sulphur is placed before chlorine in the periodic table, so it has a bigger size and its tendency to gain electrons is lesser than Cl.