Question

A single electron in an ion has an ionization energy equal to 217.6 eV. What is the total number of neutrons present in one such ion?

• A. 2
• B. 4
• C. 5
• D. 9

Answer 1

The correct option is C 5

It should be a hydrogen like species and we know that ionisation energy for a hydrogen like species:
$I.E=13.6\times \frac{Z^2}{n^2}$
$n=1$
$217.6=13.6\times Z^2$
$Z=4$
$Be$ atom for $Z=4$
Number of neutrons $\Rightarrow atomicmass-atomicnumber$
$5$