Atoms, Elements and Compounds

Atoms, Elements and Compounds

1. Atoms

   • Have a small central nucleus made up of protons and neutrons around the electrons.
   • The electrons are involved in chemical reactions
   • All substances are made up of atoms
   • About 100 different types
   • Form chemical bonds by losing, gaining or sharing a small number of electrons
   • Represented by a chemical symbol
   • When 2 or more atoms join together a molecule is formed
   • Atoms in elements and compounds are held together by taking or sharing electrons
   • Proton
     • Positive charge
     • Found in nucleus
   • Electron
     • No mass
     • Negatively charged
     • Found orbiting the nucleus in electron shells
   • Neutron
     • Neutral charge
     • Found in nucleus
   • Nucleus
     • Found in the middle of the atom
     • Contains protons and neutrons

2. Elements

   • A substance which contains one type of atom
   • Are listed in the periodic table
   • Atoms can have different numbers of protons, neutrons and electrons. It is the number of protons that decide which kind of atom it is

3. Compounds

   • Contain 2 or more elements bonded together
     • e.g hydrogen and oxygen = water