When an atom emits an alpha particle, what happens to its mass number?*1 pointincreases by 2decreases by 2increases by 4decreases by 4

Break Down the Problem

1. Identify the type of particle emitted by the atom, which is an alpha particle.
2. Understand how the emission of an alpha particle affects the atom's mass number.

Relevant Concepts

1. An alpha particle consists of 2 protons and 2 neutrons, which is essentially the nucleus of a helium atom.
2. The mass number of an atom is defined as the total number of protons and neutrons in its nucleus.

Analysis and Detail

1. When an atom emits an alpha particle:
   • It loses 2 protons and 2 neutrons.
   • Therefore, the decrease in mass number is given by the equation: $\text{New Mass Number} = \text{Original Mass Number} - 4$
   • Hence, the mass number decreases by 4.

Verify and Summarize

After analyzing the emission of an alpha particle and the corresponding changes to the atom's mass number, we confirm that the mass number decreases by 4.

Final Answer

The mass number decreases by 4.