An atom is the smallest unit of an element that keeps its chemical properties. The parts of an atom that give them their properties are called subatomic particles.
The most common types of subatomic particles are protons, neutrons, and electrons.
Protons are contained in the centermost part of the atom containing most of the mass of the atom called the nucleus. Protons have a relative charge of +1. The mass of a proton is 1 atomic mass unit (amu).
Neutrons are contained in the nucleus of the atom. Neutrons aid in stabilizing protons in the nucleus and preventing them from being attracted to the negative charge of electrons. Neutrons have a relative charge of 0. The mass of a neutron is 1 atomic mass unit (amu).
Electrons are arranged around the nucleus and have a relative charge of -1. The mass of a electron is 0.0005atomic mass units (amu). For most purposes the mass of an electron is estimated to be 0.