A+2is isoelectronic with 'CO2' & has ( z+2 ) neutrons.
(A) Mass no. of A+2is 50
(B) Last electron enters in 's' orbital in element A
(C) No. of Unpaired electron in A is 4
(D) During formation of A+2, electrons are removed from both s & d subshell.
The total number of electrons in carbon dioxide molecule is 22. As the A2+ ion is isoelectronic with CO2, therefore the number of electrons (and hence protons) in A are 22 + 2 = 24. The number of neutrons (as given) are z + 2 = 24 + 2 = 26. So the mass number is (24 + 26) = 50. Therefore mass number of A2+ ion will be 48. Also, as the atomic number of teh element is 24, therefore the electronic configuration is 4s13d5. Thus the last electron enters the d orbital and number of unpaired electrons in d-orbitals are 5. So the correct answer is (d) -during formation of A+2, electrons are removed from both s and d subshell.