Which one has the bigger size?

Na (11) or Cl (17); Cl (17) or F (9)

(i) Na has bigger size than Cl 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.

(ii) Cl has bigger size than F because number of shells increases down a group. So the size of atom also increases down a group.


11