2.1 Atomic structure and isotopes

• Atoms are made from subatomic particles called protons, neutrons and electrons
• Protons and neutrons are located in the nucleus of the atom while electrons are located in the outer shell of the atom
• Relative mass of protons and neutrons are 1, and 1/2000 for electrons
• Relative charge of a proton is +1
• Relative charge of a neutron is 0
• Relative charge of an electron is -1
• Isotopes are atoms of the same element with different number of neutrons
• Chemical properties of an element are determined by the number of electrons in the outer shell