Question

Which of the following concerning nuclear chemistry is/are incorrect?

	1.	Beta particle emission produces a nucleus with one additional neutron and one additional proton.
	2.	No stable nuclides are known above atomic number 83.
	3.	In electron capture a proton is converted to a neutron through the capture of an inner orbital electron.

a. 1 only

b. 2 only

c. 3 only

d. 2 and 3

e. 1, 2, and 3

Answer 1

Correct answer is d. 2 and 3 are correct.

1. This is incorrect. A beta particle is formed when a neutron is converted into a proton and a high energy electron. The proton remains in the nucleus and the electron the atom as a beta particle. Thus during beta decay:- mass number remains the same, nuclear charge increases by +1 due to the additional proton, and the atomic number remains the same.

So the nucleus has only an additional proton and no additional neutron. Hence this statement is incorrect.

2. This is correct. No stable nuclides are known above atomic number 83. With increase in atomic number the number of neutron exceeds the number of protons, which results in an unstable N:Z ratio i.e., neutron to proton ratio. The ratio increases significantly after atomic number 83 which leads to formation of unstable radioactive nuclides.

3. This is correct. Electron capture is also known as K capture. During electron capture, an electron present in the innermost shell (K-shell) of atom, is drawn into the nucleus where it combines with a proton to form a neutron and a neutrino. The neutrino is ejected from the nucleus of the atom. Hence this statement is correct.