* Beta radiation involves the emission of either an electron (beta-minus decay) or a positron (beta-plus decay).

* In beta-minus decay, a neutron within the nucleus transforms into a proton, an electron, and an antineutrino. The electron is emitted as beta radiation. Since a neutron becomes a proton, the atomic number of the atom increases by one.

* In beta-plus decay, a proton within the nucleus transforms into a neutron, a positron, and a neutrino. The positron is emitted as beta radiation. Since a proton becomes a neutron, the atomic number of the atom decreases by one.

* Alpha radiation involves the emission of an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. This results in a decrease of the atomic number by two.

* Gamma radiation is electromagnetic radiation with very high energy. It does not involve changes in the nucleus and therefore does not affect the atomic number.

* Neutron radiation involves the emission of neutrons, which are neutral particles. While these can be absorbed by nuclei and cause changes in atomic number, this is not a direct process of radiation emission like the other options.

In summary: Only beta radiation directly increases the atomic number of an atom by one, specifically through beta-minus decay.