Atoms and isotopes

• At the centre of every atom there is a tiny nucleus made up of protons and neutrons.
• This nucleus is orbited by negative electrons
• What are the charges and mass of each subatomic particle?

  Proton: +1 charge, 1 atomic mass unit (amu) Neutron: 0 charge, 1 amu Electron: -1 charge, negligible mass
• The total number of protons and neutrons in an atom is called its mass number.
• The number of protons determines what element an atom is. This is called its atomic number.
• Isotopes have different numbers of neutrons but the same number of protons so they all have the same atomic number.
• Isotopes are different versions of the same element
• Isotopes have the same chemical formula and are named by the relative mass of their nuclei