Question 30.CA.1: A change in charge An element of atomic number 84 decays rad...
A change in charge
An element of atomic number 84 decays radioactively to an element of atomic number 83. Which of the following emissions achieves this result?
A. Alpha particle only
B. Beta particle only
C. Alpha particle plus beta particle
A change in atomic number from 84 to 83 means that the number of protons in the nucleus has decreased by 1. The emission of an alpha particle removes two protons from the nucleus. The emission of a beta particle (an electron) means that a neutron has changed to a proton plus the emitted electron, so the atomic number increases by 1.
The emission of an alpha particle and a beta particle gives the desired result, so the correct answer is C. (So would the emission of a positron; during positron emission, a proton changes to a neutron plus the emitted positron.)