Question

Which one has the smaller size? 

K (19) or Na (1); B (5) or C (6)

Comments

Thank u so much for helping

Answer 1

(i) Na has the smaller size than K because number of shells increases down a group. So the size of atom increases down a group. Hence K is bigger and Na is smaller. 

(ii) C has smaller size than B because effective nuclear charge increases from left to right in a period. Due to this effective nuclear charge, the electronegativity increases and the attraction of nucleus on valence shell electrons also increases. So the size of atom reduces. Hence C has smaller size.