The mass number of an element represents the total number of protons and neutrons in the nucleus of an atom. Gallium (symbol: Ga) has an atomic number of 31, which means it has 31 protons. To determine the mass number, you would need to know the specific isotope of gallium.
The most common isotope of gallium is gallium-69, which has 31 protons and 38 neutrons. Therefore, the mass number of gallium-69 is 31 + 38 = 69.
It's important to note that gallium has other isotopes with different numbers of neutrons, such as gallium-67 and gallium-71, but gallium-69 is the most abundant isotope.