Question

Is K or k+ larger? explain why?

Answer 1

K is larger than K+. Because when one electron is removed from K atom , it has only 18 electrons. But nucleus contains 19 protons. So the protons will attract the electrons with greater affinity. Hence K+ ion shrinks. K is larger than K+

Answer 2

K is larger than K+

SOLUTION:

Size of the neutral K atom is larger than the cation K+ atom. This is because size of atom depends on the distance of the outermost electrons from the nucleus. These are electrons with “highest energy level”. When at neutral, the potassium ion in the form of K has an electronic configuration of:

$\mathrm{K} : 1 \mathrm{s}^{2} 2 \mathrm{s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{s}^{2} 3 \mathrm{p}^{6} 4 \mathrm{s}^{1}$

The size of the potassium ion depends on the location of the single electron, present on fourth energy level which is the highest, from the nucleus.

The cation of K+ is formed when K loses this outermost single electron to attain “electronic configuration” of:

$\mathrm{K}+: 1 \mathrm{s}^{2} 2 \mathrm{s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{s}^{2} 3 \mathrm{p}^{6}$

The K+ ion has its outermost electrons on the third energy level now and is size is smaller than that of K ion.

Hence, K is larger than K+.