(I)Write the electronic configurations of the following ions:(a) $\mathrm{H}^{-}$ (b) $\mathrm{Na}^{+}$ (c) $\mathrm{O}^{2-}$ (d) $\mathbf{F}^{-}$

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(I)Write the electronic configurations of the following ions:(a) $\mathrm{H}^{-}$ (b) $\mathrm{Na}^{+}$ (c) $\mathrm{O}^{2-}$ (d) $\mathbf{F}^{-}$

CBSE | Chemistry | Class 11 | NCERT | Structure of Atom

(I)Write the electronic configurations of the following ions:(a) $\mathrm{H}^{-}$ (b) $\mathrm{Na}^{+}$ (c) $\mathrm{O}^{2-}$ (d) $\mathbf{F}^{-}$

The electronic configuration of the Hydrogen atom (in its ground state) $1 \mathrm{~s}^{1}$ . The single negative charge on this atom indicates that it has gained an electron. Hence, the electronic configuration of $\mathrm{H}^{-}=1 \mathrm{~s}^{2}$
(b) $\mathrm{Na}^{+}$ ion
Electron configuration of $\mathrm{Na}=1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{~s}^{1} .$ Here, the +ve charge indicates the loss of an electron. $\therefore$
Electronic configuration of $\mathrm{Na}^{+}=1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{6}$
(c) $\mathrm{O}^{2-}$ ion
Electronic configuration of 0 xygen $=1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{4}$ . The ‘- 2 ‘ charge suggests that it has gained 2 electrons. $\therefore$
Electronic configuration of $\mathrm{O}^{2-}$ ion $=1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{6}$
(d) $F^{-}$ ion
Electronic configuration of Fluorine $=1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{5}$ . The species has gained one electron (accounted for by the $-1$ charge). $\therefore$ Electron configuration of $F^{-}$ ion $=1 s^{2} 2 s^{2} 2 p^{6}$