The increasing order of e/m values for electron, proton, neutron and alpha particle is

Let us see below for the mass of different fundamental particles and alpha particle.

$\mathrm{Mass} \mathrm{of} \mathrm{electron}, {\mathrm{m}}_{\mathrm{e}}=9.109\times {10}^{-31} \mathrm{kg}$

$\mathrm{Mass} \mathrm{of} \mathrm{proton}, {\mathrm{m}}_p=1.673\times {10}^{-27} \mathrm{kg}$

$\mathrm{Mass} \mathrm{of} \mathrm{neutron}, {\mathrm{m}}_{\mathrm{e}}=1.675\times {10}^{-27} \mathrm{kg}$

Mass of alpha particle, ${\mathrm{m}}_{\mathrm{\alpha }}=4\mathrm{g}$

$\mathrm{Case}-1:\frac{\mathrm{e}}{\mathrm{m}} \mathrm{of} \mathrm{electron}=\frac{1.602\times {10}^{-19}\mathrm{C}}{9.109\times {10}^{-31}\mathrm{kg}}=1.75\times {10}^{11}\mathrm{C}.{\mathrm{kg}}^{-1}$

$\mathrm{Case}-2:\frac{\mathrm{e}}{\mathrm{m}} \mathrm{of} \mathrm{proton}=\frac{1.602\times {10}^{-19}\mathrm{C}}{1.673\times {10}^{-27}\mathrm{kg}}=9.5\times {10}^7\mathrm{C}.{\mathrm{kg}}^{-1}$$\mathrm{Case}-3:\frac{\mathrm{e}}{\mathrm{m}} \mathrm{of} \mathrm{\alpha } \mathrm{particle}=\frac{2\times 1.602\times {10}^{-19}\mathrm{C}}{4\times {10}^{-3}\mathrm{kg}}=8.01\times {10}^{17}\mathrm{C}.{\mathrm{kg}}^{-1}$$\mathrm{Case}-4:\frac{\mathrm{e}}{\mathrm{m}} \mathrm{of} \mathrm{neutron}=\frac{0}{1.675\times {10}^{-27}\mathrm{kg}}=0$

Note: Since neutron is charge less particle.

Therefore, increasing order of e/m ratio for electron , proton, neutron & alpha particle is $\mathrm{n}<\mathrm{\alpha }<\mathrm{p}<{\mathrm{e}}^{-}.$