In each of the following pairs, which species has a larger size? Explain. (i) Kor K+
K is larger in size than K+. The electronic configurations of K and K+ are: K: 1s2, 2s2 2p6, 3s2 3p6, 4s1 K+: 1s2, 2s2 2p6, 3s2 3p6.K+ is formed from K when the latter loses its 4s electrons. K → K+ + e– As seen from the electronic configurations of K and K+, the K+ ion has 18 electrons and the K atom has 19 electrons but the nuclear charge in both these species is the same (+ 19). Since the K+ ion has 1 electron less than the K atom, the forces of attraction between the nucleus and the electrons are more strong in the K+ ion than in the K atom. This results in more inward pulling of electrons towards the nucleus in K+ ion and hence its size decreases.
