Question

an atom that has 84 protons and 86 neutrons undergoes a reaction. at the end of the reaction, it has 82 protons and 84 neutrons. what happened to the atom?

it accepted radiation in a chemical reaction.

it donated neutrons to another atom in a chemical reaction.

it emitted an alpha particle in a nuclear reaction.

it released a beta particle in a nuclear reaction.

Explanation:

1. First, analyze the change in protons and neutrons: Initial protons = 84, neutrons = 86; Final protons = 82, neutrons = 84. The change in protons is \(84 - 82 = 2\), and the change in neutrons is \(86 - 84 = 2\).
2. An alpha particle (\(\alpha\)) has 2 protons and 2 neutrons. Chemical reactions do not change the number of protons (atomic number), so this is a nuclear reaction. Emitting an alpha particle reduces protons and neutrons by 2 each, matching the change here. Beta particle emission changes neutron to proton (or vice - versa) and doesn't reduce both by 2. Donating neutrons or accepting radiation in chemical reactions don't change atomic number (protons), so they are incorrect.

Answer:

It emitted an alpha particle in a nuclear reaction.