Question

Write electron configuration for the following ions: (i) Fe3+ (ii) Cr3+ (iii) Pb2+ (iv) Pb4+ (v) O2

Answer 1

1. 1s2 2s2 2p6 3s2 3p6 4s2 3d3
2. 1s2 2s2 2p6 3s2 3p6 4s2 3d1
3. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 5s1 4d7
4. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 5s1 4d5
5. (I am sorry, but O2 is not an ion it is a molecule)

Answer 2

STEP 1 write down the electron configuration of the atom, Fe. STEP 2 The ion has a 3+ charge so three electrons are removed. Two are taken from the 4s sub-shell, the other from the 3d sub-shell. So the electron configuration of Fe3+ is: 1s2 2s2 2p6 3s2 3p6 3d5.Cr3+:1s22s2: o2 [He] 2s2 2p4