Question

Discuss the beta decay process with examples.

Answer 1

In beta decay, a radioactive nucleus emits either electron or positron. If electron (e^–) is emitted, it is called β^– decay and if positron (e⁺) is emitted, it is called p+ decay. The positron is an anti-particle of an electron whose mass is the same as that of an electron and the charge is opposite to that of an electron – that is, +e. Both positron and electron are referred to as beta particles.

1. β^– decay:
   In β^– decay, the atomic number of the nucleus increases by one but the mass number remains the same. This decay is represented by
   \[\ce{^A_ZX -> ^A_{Z + 12}Y + e- + \bar{v}}\]   .....(1)
   It implies that the element X becomes Y by giving out an electron and antineutrino `(bar"v")`. In otherwords, in each β^– decay, one neutron in the nucleus of X is converted into a proton by emitting an electron (e^–) and antineutrino. It is given by n → p + e^– + `bar"v"`
   Where p -proton, `bar"v"`-antineutrino. Example: Carbon \[\ce{^14_6C}\] is converted into nitrogen \[\ce{^14_7N}\] through β- decay.
   \[\ce{^14_6C -> ^14_7N + e- + \bar{v}}\]
2. β⁺ decay:
   In p+ decay, the atomic number is decreased by one and the mass number remains the same. This decay is represented by
   \[\ce{^A_ZX ->^A_{Z-12}Y + e+ + \text{v}}\]
   It implies that the element X becomes Y by giving out a positron and neutrino (v). In otherwords, for each β⁺ decay, a proton in the nucleus of X is converted into a neutron by emitting a positron (e⁺) and a neutrino. It is given by
   p → n + e⁺ + v
   However a single proton (not inside any nucleus) cannot have β⁺ decay due to energy conservation, because neutron mass is larger than proton mass. But a single neutron (not inside any nucleus) can have β^– decay.
   Example: Sodium \[\ce{^23_11Na}\] is converted into neon \[\ce{^22_10Ne}\] 
   decay.
   \[\ce{^23_11Na -> ^22_10Ne + e+ + \text{v}}\]