Question

The increasing order for the value of charge/mass for electron (e), proton (p), neutron (n) and alpha particle $(\alpha )$ is:

• A. $e<p<n<a$
• B. $n<p<e<\alpha$
• C. $n<p<\alpha <e$
• D. $n<\alpha <p<e$

Answer 1

Answer: (D)

Find e/m (charge/mass) of all the given particles and then arrange them in given order.
(i) e/m of electron $=\frac{1.6\times {10}^{-19}}{9.1\times {10}^{-28}}=0.175\times {10}^9$
(ii) e/m of proton $=\frac{1.6\times {10}^{-19}}{1.673\times {10}^{-24}}={10}^5$
(iii) e/m of neutron $=\frac{0}{1.673\times {10}^{-24}}=0$
(iv) e/m of $\alpha -$ particle $=\frac{2\times 1.6\times {10}^{-19}}{4\times 1.67\times {10}^{-24}}=0.5\times {10}^5$
$\therefore$ The correct order is $n<\alpha <p<e$