Which of the following decays result in a decrease in the atomic number?

Step-by-step solution

In -decay, the nucleus emits an -particle ( ⁴₂ He ). The atomic number Z decreases by 2 . In ⁺ -decay, a proton is converted into a neutron with the emission of a positron ( ⁰_ +1 e ). The atomic number Z decreases by 1 . In ⁻ -decay, a neutron is converted into a proton with the emission of an electron ( ⁰_ -1 e ). The atomic number Z increases by 1 . In -decay, only the energy state of the nucleus changes. The atomic number Z remains unchanged. Thus, -decay and ⁺ -decay result in a decrease in the atomic number.