Question

Which of the following Element show variable valency?
(a) Na
(b) Mg
(c) Fe
(d) Zn
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Answer 1

Answer:

(c) Fe

IRON

Explanation:

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Answer 2

Iron (Fe) shows variable valency.

Explanation:

Iron is placed in group 8 on the periodic table. It is a transition metal. The electronic configuration of Iron is $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6}4s^{2} 3d^{6}$.

Iron shows variable valency $+2\ and +3$.

$For +2\\Iron\ loses\ the\ two\ electrons\ from\ the\ outermost\ shell\ 4s^{2}\\Electronic\ configuration\ for\ Fe^{+2} = 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6}$

$For +3\\Iron\ loses\ the\ two\ electrons\ from\ the\ outermost\ shell\ 4s^{2} \\ one\ electron\ from\ second\ last\ shell\ 3d^{6} to\ obtain\ stable\ half-filled\ configuration \\\\Electronic\ configuration\ for\ Fe^{+2} = 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{5}$

Half-filled and full-filled orbitals provide extra stability to the atom.