Fundamental Ideas

Fundamental Ideas

1. Atoms have no charge

   • Number of protons = number of electrons
     • +ve = -ve

2. Charge on electrons is the same size as the charge on protons, just the opposite charge

3. When electrons are gained or lost from an atom, it becomes a charged ion

   • Gain = positive Lose = negative

4. Group number in the periodic table = number of outer electrons

5. Energy shell closest to the nucleus has the lowest energy

   • it's harder to lose because its less reactive - the attraction between it and the nucleus is stronger because it's closer. energy shell on the outside has more energy so it is more reactive and therefore easier to lose

6. A compound is when two or more atoms join together in a bond

   • Ionic bond = transferring atoms
   • Covalent bonding = sharing atoms
     • atoms make enough covalent bonds to have full outer shells
   • Compounds with metals AND non-metals contain ions
     • when non-metals lose electrons it becomes negative. when metals lose electrons, it becomes positive
   • Compounds with just non-metals contain molcules
   • Compounds have completely different properties to the elements they contain

7. mass number = protons + neutrons

   • atomic number = number of protons (which is the same as the number of electrons
   • mass - atomic = number of neutrons