# What gives an elemental atom its weight?

In an isolated atom, or indeed in a collection of atoms, most of the mass is concentrated in the nucleus, which is itself composed of massive fundamental particles: $\text{protons}$, massive particles that are positively charged; and $\text{neutrons}$, massive particles that are neutrally charged. The mass of protons and neutrons are roughly equivalent, and their short range interaction overcomes electrostatic repulsion, and binds the nucleus together.