Question

The pair of atomic numbers which belong to the same group :

• A. 9, 14
• B. 17, 51
• C. 6, 53
• D. 12, 56

Answer 1

The correct option is D 12, 56

The elements in option D with atomic number 12 and 56 are magnesium and barium. Both are in Group 2 of the periodic table as each has 2 elements in the valence shell

Electronic Configuration of Barium:

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{6}4d^{10}5s^{2}5p^{6}6s^2$

Electronic Configuration of magnesium:

$1s^{2}2s^{2}2p^{6}3s^2$