SAT Subject Physics Practice Question 238: Answer and Explanation
9. Which type of decay would cause the atomic number of the nucleus to increase?
A. Alpha decay
B. β– decay
C. β+ decay
D. Electron capture
E. Gamma decay
Correct Answer: B
When a nucleus undergoes β– decay, a neutron is converted into a proton and an electron, and the electron is ejected. Because of this, the number of protons in the nucleus—the atomic number—is increased by 1.