Radioactive decay is a natural process by which unstable atomic nuclei transform into more stable configurations by emitting particles or energy. Each type of decay affects the atomic number and/or mass number differently.

Alpha Decay (α decay)

In alpha decay, the nucleus emits an alpha particle, which consists of 2 protons and 2 neutrons. This reduces the atomic number by 2 and the mass number by 4.

Example: \(\ce{^{238}_{92}U -> ^{234}_{90}Th + ^{4}_{2}He}\)

Beta-minus Decay (β⁻ decay)

In beta-minus decay, a neutron in the nucleus converts into a proton and emits a beta-minus particle (an electron) and an antineutrino. The atomic number increases by 1.

Example: \(\ce{^{14}_{6}C -> ^{14}_{7}N + \beta^- + \bar{\nu}_e}\)

Beta-plus Decay (β⁺ decay / Positron Emission)

In beta-plus decay, a proton transforms into a neutron, emitting a positron (β⁺) and a neutrino. The atomic number decreases by 1.

Example: \(\ce{^{11}_{6}C -> ^{11}_{5}B + \beta^+ + \nu_e}\)

Electron Capture (EC)

In electron capture, an inner orbital electron is captured by the nucleus and combines with a proton to form a neutron. This process emits a neutrino and decreases the atomic number by 1.

Example: \(\ce{^{7}_{4}Be + e^- -> ^{7}_{3}Li + \nu_e}\)

Gamma Emission (γ decay)

Gamma decay often follows beta minus decay when the resulting nucleus is left in an excited state, leading to the emission of a gamma ray (high-energy photon). Gamma emission does not change the atomic number or mass number, whereas beta minus decay does. The example below will help you understand this more clearly.

Example: \(\ce{^{60}_{27}Co -> ^{60}_{28}Ni + \beta^- + \gamma}\)

Summary Table

Decay Type	Emission	Change in Atomic Number	Change in Mass Number
Alpha (α)	He nucleus (2p, 2n)	-2	-4
Beta-minus (β⁻)	Electron + antineutrino	+1	0
Beta-plus (β⁺)	Positron + neutrino	-1	0
Electron Capture	Neutrino	-1	0
Gamma (γ)	Gamma photon	0	0