Chemistry Revision

Chemistry Revision

1. Structure of the atom

   • Has a nucleus
   • Nucleus has Protons in it
     • These are positively charged
   • Nucleus has neutrons in it
     • These are neutrally charged
   • Atom has a shell around the outside
   • Shell contains electrons
     • Electrons are negatively charged

2. Isotopes

   • An isotope is when the number of neutrons is less than the number of protons, it becomes an atomic number
   • E.g. if the mass number= 35, we do the mass number minus the atomic number. This will give you the number of neutrons. If the atomic number is 17 then 35-17= 18. This is an isotope.

3. Ions

   • An atom can lose/ gain electrons. When this happens, it becomes an ion.
   • When an atom loses an electron it becomes positively charged, as the atom has lost a negative charge
   • When an atom gains an electron, it becomes negatively charged because it has gained a negative charge.

4. Calculating Protons, Neutrons and Electrons

   • The amount of protons and electrons is the mass number
   • To find the number of neutrons, do the atomic number minus the mass number.