Atoms of the same element that have the same number of protons but different numbers of neutrons, i.e. they have the same atomic number but a different mass number
Ions
Atoms that have gained or lost electrons, giving them a positive or negative charge
Chlorine isotopes
35Cl
37Cl
Chlorine isotopes
17 protons
17 electrons
35 neutrons
37 neutrons
Sodium atom
11 protons
11 electrons
12 neutrons
Sodium ion
11 protons
10 electrons
12 neutrons
Metal atoms lose electrons to form positive ions
Non-metal atoms gain electrons to form negative ions
