Find the mass number of both the ions

cbse
structureofatom

#1

Two ions having 3 negative and 3 positive charges are found to have 7 and 14 neutrons respectively. If electronic configuration of these ions are similar to that of neon (Ne), then find the mass number of both the ions.


#2

The electronic configuration of Ne= 2, 8
Atom, which forms ion with 3 positive charges, will have electronic configuration as = 2, 5(K,L)
Hence, the given atom is nitrogen.
Mass number = Number of protons + number of neutrons = 7 + 7 = 14
Similarly, atom which forms ion with 3 negative charges, will have electronic configuration as = 2, 8, 3 (K,L,M)
Hence, the given atom is aluminium.
Mass number = Number of protons + number of neutrons
= 13 + 14 = 27