Explanation:
Atomic size
in is defined as size of on atom or distance from nucleus to outermost shell of an atom.
ALONG GROUP --> it increases.
For example:- Consider 1st group
Li – 3 2,1 K,L
Na- 11 2,8,1 K, L, M
K- 19 2, 8, 8, 1 K,L, M, N
As we move down the group. , every time a new shell is being added due to which size of an atom increases.
Along period - it decreases.
For example:- consider 3rd period
Na Mg Ar Si
2,8,1 2,8,2 2,8,3 2,8,4
We see every time, a new electron is added to the same shell due to which nuclear charge increases and size decreases.
That is the reason ,In the above asked question : out of all K is bigger .
