Tritium, a radioactive isotope of hydrogen, emits which of the following particles ?

Tritium ($³H_{}$) is a radioactive isotope of hydrogen that contains one proton and two neutrons in its nucleus.

Because it has an excess of neutrons, tritium undergoes a transformation in which one of its neutrons is converted into a proton. This nuclear change can be expressed as:

$n\to p+e-+\nu$_̅

In this reaction, the neutron (n) changes into a proton (p) and releases an electron (e⁻) and an antineutrino (ν_̅). The emitted electron is the particle known as a beta‑minus (β⁻) particle.

Consequently, the decay of tritium can be written as:

${³}^{\mathrm{H}}\to {³}^{\mathrm{He}}+\beta -+\nu$_̅

Therefore, the particle emitted by tritium is a beta‑minus particle.