(i) Write the electronic configurations of the following ions:
(a) `H^- (b) Na^+ (c) O^(2-) (d) F^-`
(ii) What are the atomic numbers of elements whose outermost electrons are represented by
`(a) 3s^1 (b) 2p^3 and (c) 3p^5 ?`
(iii) Which atoms are indicated by the following configurations?
`(a) [He]2s^(1) (b) [Ne] 3s^2 3p^3 (c) [Ar] 4s^2 3d^1`.

Explanation

(i) `(a) H^(-) , 1s^(2) (b) Na^(+) : 1s^(2) 2s^(2) 2p^(6)`
(c) `O^(2-), 1s^(2) 2s^(2) 2p^(6) (d) F^(-), 1s^(2) 2s^(2) 2p^(6)`
(ii) `(a) 1s^(2) 2s^(2) 2p^(6) 3s^(1) (Z=11)`
(b) `1s^(2) 2s^(2) 2p^(3) (Z=7)`
(c) `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(5) (Z=17)`
(iii) (a) `1s^(2) 2s^(1)`, then atom is Li
(b) `1s^(2) 2s^(2) 2p^6 3s^(2) 3p^3`, the atom is P.
(c) `1s^2 2s^2 2p^6 3s^2 3p^6 3d^1 4s^2`, the atom is Sc.