Question

which has highest e/m ratio

a) he 2+

b)h

C)H+

d) he+

Answer 1

The highest e/m ratio is H+

Answer 2

The highest value of e/m ratio is $\bold{\mathrm{C} )\ \mathrm{H}^{+}}$.

We know that e/m is the charge to mass ratio for the given atom of the nucleus. Here ‘e’ stands for charge whereas ‘m’ stands for mass.  

In $\mathrm{He}^{+2}$ ion, the charge is 2 (e) and mass is 4(m) hence $\frac{e}{m}=\frac{2}{4}=0.5$.

For H atom the charge is 0 so e/m ratio will be 0 whereas for $\mathrm{H}^{+}$; the value of e is 1 and mass is also 1. Hence the e/m ratio for $\mathrm{H}^{+}$ ion must be $\frac{1}{1}=1$ whereas for $\mathrm{He}^{1+}$ ion, it is $\frac{1}{4}=0.25$.

Overall the highest value of e/m ratio is for $\bold{\mathrm{H}^{+}}$ ion.