Question

The nucleus B (with 84 protons and 126 neutrons) emits a β particle and is transformed into a nucleus C. What is the composition of C?
A) 83 proton and 125 neutrons
B) 85 proton and 125 neutrons
C) 84 proton and 125 neutrons
D) 83 proton and 126 neutrons

Answer 1

Hint
As beta decays occur in two ways-
Beta minus decay: when the nucleus emits an electron and an antineutrino in a process that changes a neutron to a proton.
Beta –plus decay:. When the nucleus emits a positron and a neutrino in a process that changes a proton to a neutron this process is called positron emission.
Here in the given question Nucleus emits a β particle and is transformed into a nucleus C so it is the case of the beta minus decay. Here in this case a neutron changes into the proton.

Complete step by step answer
According to the given question, the nucleus changes to nucleus C by emitting a β particle hence it leads to the conversion of neutrons into protons.
So 1 proton increases in the nucleus and one neutron decreases to form the new nucleus C.
So now in the nucleus of C, the number of protons is 84+1 = 85 protons.
Or the number of neutrons gets, 126-1 = 125 neutrons.
So the correct answer is given by 85 protons and 125 neutrons.
So the correct option is (B).

Note
In gamma decay a radioactive nucleus first decays by the emission of an alpha particle or beta particle. The daughter nucleus that results is usually left in an excited state and it can decay to a lower energy state by emitting a gamma ray proton.