# A certain atom has 26 protons, 26 electrons, and 30 neutrons. What is its mass number?

Its $\text{mass number}$ is $56$.
Mass number is simply the total number of massive particles in the atom, protons and neutrons. There are 26 protons, and 30 neutrons, and thus its $\text{mass number}$ $=$ $56 \cdot \text{amu}$.