1(viii)
An atom of X forms an ion according to the equation X ⟶ X+2.
The atomic number of the atom X is:
- (a)16
- (b)10
- (c)12
- (d)14
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12
Reason — An element with atomic number 12 has the electronic configuration 2, 8, 2. It loses its 2 valence electrons easily to attain a stable octet configuration (2, 8) and forms a divalent positive ion X2+. This element is magnesium (Mg).
Mg ⟶ Mg2+ + 2e-
Whereas, atomic number 16 (Sulphur) gains 2 electrons to form S2-, atomic number 10 (Neon) is a noble gas which doesn't form ions, and atomic number 14 (Silicon) shares electrons.