MCQ
The first ionization energy (in $\mathrm{kJ} / \mathrm{mol}$ ) of $Na, \;\mathrm{Mg}, \mathrm{Al}$ and $Si$ respectively, are
- ✓$496,737,577,786$
- B$786,737,577,496$
- C$496,577,737,786$
- D$496,577,786,737$
${\mathrm{Mg}=[\mathrm{Ne}] 3 \mathrm{s}^{2}}$
${\mathrm{Al}=[\mathrm{Ne}] 3 \mathrm{s}^{2} 3 \mathrm{p}^{1}}$
So order of first ionisation energy is
$\mathrm{Na}(496)<\mathrm{Mg}(737)>\mathrm{Al}(577)<\text { Si }{(786)}$
$\mathrm{Na}<\mathrm{Al}<\mathrm{Mg}<\mathrm{Si}\left(\mathrm{IE}_{1} \text { order }\right)$
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[Atomic mass $: \mathrm{Na}=23.0, \mathrm{O}=16.0, \mathrm{H}=1.0]$