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# The increasing order for the values of e/m (charge/mass) for the electron (e), proton (p), neutron (n) and alpha particle (${{\alpha }}$) is:A.e, p, n, ${{\alpha }}$B.n, p, e, ${{\alpha }}$C.n, p, ${{\alpha }}$, eD.n, ${{\alpha }}$, p, e

Last updated date: 09th Aug 2024
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Hint:Charge to mass ratio (e/m) is a physical quantity that is most widely used in the electrodynamics of the charged particles.
Knowing the value of charge to mass ratio helps us to calculate the mass of that charged particle by measuring charge effects.
Each charged particle has its charge to mass ratio.
Let us now calculate the charge to mass ratio of each one of the given charged particle:
Electron (e):
The charge on electron is taken as 1 (negative) and the mass of electron is ${{{1}}}{{{{1837}}}}$ u
And thus, e/m for electrons is: ${1}{{ {1}{{1837}}}}$ = 111837.
Neutron (n):
The charge on the neutron is zero and thus its charge to mass ratio is also zero.
Proton (p):
The charge on a proton is 1 (positive). And its mass is also 1 u.
Thus, e/m for proton is 1.
Alpha particle (${{\alpha }}$):
The charge on an alpha particle is 2 and its mass is 4. Which gives us the charge to mass ratio of alpha particle as ${{{2}}}{{{4}}}{{ = 0}}{{.5}}$
Arranging all the calculated values of charge-to-mass ratio of all the given particles in increasing order we have: n, p, ${{\alpha }}$, e.

Hence, the correct option is D.

Note: Please note that electrons, protons, and neutrons are the constituents of an atom. While alpha particles or alpha rays consist of two protons and two neutrons bound together into a particle which is identical to the Helium-4 nucleus. Alpha-rays are emitted during a nuclear reaction. There are charged rays similar to alpha rays such as beta rays but these are negatively charged, unlike alpha rays which are positively charged.