Question

A sudden jump between the values of second and third ionization energies of an atom would be associated with the electronic configuration :

• A. ${1s}^2,{2s}^2,{2p}^6{}^{}{}^{}$
• B. ${1s}^2,{2s}^2{2p}^6,{3s}^2,{3p}^1$
• C. ${1s}^2,{2s}^2,{2p}^6,{3s}^2,{3p}^2$
• D. ${1s}^2,{2s}^2{2p}^6,{3s}^2$

Answer 1

The correct option is D ${1s}^2,{2s}^2{2p}^6,{3s}^2$

Magnesium ${1s}^2{2s}^2{2p}^6{3s}^2$ is in group 2 of the Periodic Table and has first ionisation energy 737.7kJ/mol, second ionisation energy 1450.7 kJ/mol and third ionisation energy 7732.7 kJ/mol. Here the big jump occurs after the second ionisation energy. It means that there are 2 electrons which are relatively easy to remove the ${3s}^2$ electrons, while the third one is much more difficult because it comes from an inner level - closer to the nucleus and with less screening.