Question
Which is correct about ionisation potential
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| Energy level | $K$ | $L$ | $M$ | $N$ |
| $n=1$ | $n=2$ | $n=3$ | $n=4.....n=\infty$ | |
| Energy | $- 864 \,a.u.$ | Zero |
the excitation energy needed to raise the electron from $M$ level to $n = \infty$ would be :
$A$. $\mathrm{Be} \rightarrow \mathrm{Be}^{-}$
$B$. $\mathrm{N} \rightarrow \mathrm{N}^{-}$
$C$. $\mathrm{O} \rightarrow \mathrm{O}^{2-}$
$D$. $\mathrm{Na} \rightarrow \mathrm{Na}^{-}$
$E$. $\mathrm{Al} \rightarrow \mathrm{Al}^{-}$
Choose the most appropriate answer from the options given below :