Atoms, Elements and Compounds!

Atoms, Elements and Compounds!

1. Atoms-

   • Atoms contain protons, neutrons and electrons
     • All substances are made up of atoms. They are really tiny (too small to see.)
     • The number of protons equals the number of electrons.
       • Atomic number and Mass number describe an atom.
   • The middle of an atom is called the nucleus, it contains protons and neutrons.
     • The electrons in an atom move around the nucleus in electron shells. They are negatively charged and tiny.

2. Elements-

   • An element is a substance made up of atoms that all have the same number of protons in their nucleus.
     • Elements consist of atoms with the same atomic number.
       • There are around 100 different elements all together.
         • All atoms of each element have a set number of protons ( so that each nucleus has a given positive charge.)

3. Compounds-

   • Atoms join together to make compounds.
     • When elements react, atoms combine with other atoms to form compounds.
       • Compounds are substances formed from two or more elements.
         • The atoms of each are in fixed proportions throughout the compound and they are held together by chemical bonds.
           • A formula shows what atoms are in a compound.
             • For example- CO2 is carbon dioxide.
               • H2O is water.