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Q.
Which one of the following pair of elements has similar properties?
Rajasthan PMTRajasthan PMT 2003Classification of Elements and Periodicity in Properties
Solution:
The elements $13$ (Aluminium) and $31$ (Galium) both belong to same group i.e., III A. Therefore, both elements have similar electronic configuration of the outermost shell and hence have similar properties.
$Al \left(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{1}\right)$
$Ga \left(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{10} 4 s^{2} 4 p^{1}\right)$