Question

Two elements ‘A’ and ‘B’ have same number of electrons in their valence shells. The number of electrons present in the second last shell of atom ‘A’ is two times the number of electrons present in the second shell of atom ‘B’. A and B respectively are
(1) Aluminium and phosphorus
(2) Magnesium and calcium
(3) Silicon and carbon
(4) Oxygen and sulphu

Answer 1

Thanks for asking the question.
The correct answer is 3 that is silicon and carbon. According to the first condition given both have the same number of electrons in their valence shells that is four. According to the second condition silicon has twice the electrons in its second last shell than that of carbon.
Hope it helps.