Atoms, elements and Compounds

Atoms, elements and Compounds

1. Elements

   • A substance that is made up from only one type of atom
     • Eg. Fe, O2, Cl2
   • Physical and chemical properties of Metals
     • High melting point
     • Malleable and ductile
     • Good conductors of heat
     • Good conductors of electricity
     • Shiny
     • High Density
   • Physical and chemical properties of non-metals
     • Low melting point
     • Brittle
     • Poor conductors of heat
     • Poor conductors of electricity
     • Dull
     • low density

2. Atoms and molecules

   • An atom is the smallest particle of an element
     • For example Ar, Fe
   • Some atoms cannot exist by themselves- they have to exist in a pair by forming a chemical bond, this is a molecule
     • Eg Cl2, O2, H2, N2, F2, Br2, I2
     • joined by covalent bonds

3. Compounds and mixtures

   • A compound is a pure substance made of different types of atom that have been chemically joined together in fixed proportion
   • A mixture is made of at least two substances that have not been chemically combined