Which of the following describes radioactive decay by beta particle emission?

• A. A neutron in the nucleus is converted into a proton, and an electron (beta particle) is emitted.
• B. The nucleus emits an alpha particle consisting of two protons and two neutrons.
• C. A proton in the nucleus is converted into a neutron, and a positron is emitted.
• D. The nucleus emits a gamma ray without changing its number of protons or neutrons.

Answer: (A)

Verified step by step guidance

1. Understand that beta decay involves the transformation of a neutron into a proton or vice versa within the nucleus, accompanied by the emission of a beta particle (an electron or positron).
2. Recall that in beta minus (β⁻) decay, a neutron is converted into a proton, and an electron (beta particle) along with an antineutrino is emitted.
3. Recognize that the emitted beta particle is essentially an electron ejected from the nucleus, which increases the atomic number by 1 but leaves the mass number unchanged.
4. Differentiate beta decay from alpha decay, where an alpha particle (2 protons and 2 neutrons) is emitted, and from gamma decay, where only energy in the form of gamma rays is emitted without changing the number of protons or neutrons.
5. Note that positron emission (beta plus decay) involves a proton converting into a neutron and emitting a positron, which is different from beta minus decay.