QQuestion
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
ICSEClass 10ChemistryPeriodic Table, Periodic Properties and Variations of Properties01 Mark2026 Easy
✓Answer
(c) 12
Explanation –
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).
\mathrm{Mg \rightarrow Mg^{2+} + 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.
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