Mon February 28, 2011 By: Mohit Gehlot

Explain, with the help of a nuclear reaction in each of the following cases, how the neutron to proton ratio changes during (i) alpha- decay (ii) beta-decay?

Expert Reply
Mon February 28, 2011
Dear student,
During alpha decay, the number of protons and neutrons of the daughter nucleus decreases by two. But during beta decay, a neutron is converted into a proton and thus the atomic number increases. That is, the number of protons increases.
Alpha decay occurs when the nucleus of an atom spontaneously ejects an alpha particle. The alpha particle is the same as a helium nucleus with 2 protons and 2 neutrons. This means the number of protons in the nucleus is reduced by 2 and the total number of nucleons is reduced by 4.

241Am95 â ZXA + 4He2

A = number of protons = 95 - 2 = 93

X = the element with atomic number = 93

According to the periodic table, X = neptunium or Np.
Î²- decay occurs when a neutron converts into a proton and ejects an energetic electron called the beta particle. This means the the number of neutrons, N, is reduced by 1 and the number of protons, A, is increased by 1 on the daughter atom.

138I53 â ZXA + 0e-1

A = number of protons = 53 + 1 = 54

X = the element with atomic number = 54

According to the periodic table , X = xenon or Xe

The mass number, A, remains unchanged because the loss of one neutron is offset by the gain of a proton.
Hope this helps.
thanking you
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