Question

The spectrum of helium is expected to be similar to that of:

• A. ${\mathrm{He}}^{+}$
• B. $\mathrm{H}$
• C. ${\mathrm{Li}}^{+}$
• D. $\mathrm{Na}$

Answer 1

The correct option is C

${\mathrm{Li}}^{+}$

Explanation for the correct option:

(c ) ${\mathrm{Li}}^{+}$

• The number of electrons in ${\mathrm{Li}}^{+}$ and $\mathrm{He}$ =$2$.
• As a result, the spectrum will be the same for each of them with the same number of electrons.
• Hence this option is correct

Explanation for the incorrect options:

(a) ${\mathrm{He}}^{+}$

• The number of electrons in ${\mathrm{He}}^{+}$is $1$ which is not same as that of $\mathrm{He}$.
• Hence this option is incorrect

(b) $\mathrm{H}$

• The number of electrons in $\mathrm{H}$is $1$ which is not same as that of $\mathrm{He}$.
• Hence this option is incorrect

(d) $\mathrm{Na}$

• The number of electrons in $\mathrm{Na}$ is $11$ which is not same as that of $\mathrm{He}$.
• Hence this option is incorrect

Hence the correct option is (c ) ${\mathrm{Li}}^{+}$