Atomic Structure Basics
Every atom is made up of three fundamental particles that determine its identity and behaviour. The nucleus contains protons (charge +1, mass 1) and neutrons (charge 0, mass 1), whilst electrons (charge -1, mass 0) orbit around it.
Your atomic number tells you exactly how many protons and electrons an atom has - they're always equal in a neutral atom. The atomic mass is simply the total number of protons plus neutrons, which gives you the atom's weight.
Isotopes are atoms of the same element that have different numbers of neutrons but identical numbers of protons and electrons. For example, carbon can exist as ¹²C, ¹³C, and ¹⁴C - all with 6 protons but 6, 7, or 8 neutrons respectively. Since chemical properties depend on electrons, all isotopes of an element behave identically in reactions.
Quick Tip: Remember that atomic number = protons = electrons, whilst atomic mass = protons + neutrons.
