$(I I I)(a)[H e] 2 s^{1}$
Complete electronic configuration: $1 \mathrm{~s}^{2} 2 \mathrm{~s}{ }^{1}$.
$\therefore$ the element’s atomic number is 3 . The element is lithium (Li)
(b) $[\mathrm{Ne}] \mathrm{ss}^{2} 3 \mathrm{p}^{3}$
Complete electronic configuration: $1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{~s}^{2} 3 \mathrm{p}^{3} \ldots$ the element’s atomic number is $15 .$ The element
is phosphorus (P).
(c) $[\mathrm{Ar}] 4 \mathrm{~s}^{2} 3 \mathrm{~d}^{1}$
Complete electronic configuration: $1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{~s}^{2} 3 \mathrm{p}^{6} 4 \mathrm{~s}^{2} 3 \mathrm{~d}^{1} \ldots$ the element’s atomic number is 21 . The element is scandium (Sc).
(III) Which atoms are indicated by the following configurations? (a) $[\mathrm{He}]{2} \mathrm{~s}^{1}$ $(b)\left[\right.$ Ne] $3 s^{2} 3 p^{3}$ (c) $[\mathrm{Ar}] 4 \mathrm{~s}^{2} 3 \mathrm{~d}^{1}$
(III) Which atoms are indicated by the following configurations? (a) $[\mathrm{He}]{2} \mathrm{~s}^{1}$ $(b)\left[\right.$ Ne] $3 s^{2} 3 p^{3}$ (c) $[\mathrm{Ar}] 4 \mathrm{~s}^{2} 3 \mathrm{~d}^{1}$