2. The Periodic Table The periodic table is a list of all the known elements arranged in Groups and Periods All the elements on the LHS are metals – RHS are non – metals. A Group is a vertical column. A Period is a row.

3. Groups The elements in the same group have similar chemical properties. Group Names Group 1 - Alkali metals – very reactive metals – stored in Oil. Group 7 – Halogens – very reactive non – metals. Group 8 – The Noble Gases – very unreactive non-metal gases. Transition metals – lie between groups 2 and 3.

4. Elements Elements are made up of only one type of atom. Atoms are made up of tiny sub-atomic particles: Protons, Electrons and Neutrons. The atom is in two parts a Core in the middle – The Nucleus, and the Electron Clouds which orbit the Nucleus.

5. The Structure of the Atom The Nucleus contains Protons and Neutrons. Electrons are found in the Electron clouds. Protons: Mass =1 a.m.u, charge + Electrons: Mass=1/1850 a.m.u, charge- Neutrons:Mass 1 a.m.u, charge 0.

6. Properties of Elements Every element has a unique number called Atomic Number. The Atomic Number is the number of Protons ( this is equal to the number of electrons in a neutral atom) The Mass Number is a total of the particles with mass i.e. protons and neutrons.

7. Calculations! Number of Protons = Atomic Number. Number of Electrons= Number of protons. Number of neutrons = Mass number – Atomic Number Example Chlorine – Mass No. = 35, Atomic No. = 17 Number protons= 17, Number of electrons = 17, Number of Neutrons = 35-17 = 18.

8. Electrons Electrons are arranged inside the electron clouds. These are inside “Energy Levels” The first energy level holds a maximum of 2 electrons within 1 cloud. The second energy level can hold up to 8 electrons – in pairs in 4 clouds The third energy level also hols 8 electrons in 4 clouds.

9. Electron Arrangement This is the name given to how the electrons are organised. Example Sodium has 11 electrons. 2 will be in the first energy level, 8 in the second energy level and the one remaining electron will be in the third energy level. The electron arrangement for Sodium is written as 2,8,1.

10. Isotopes These are atoms of the same elements that have different mass numbers i.e. different numbers of neutrons. Example Chlorine – has 2 isotopes – one has a mass of 35 a.m.u. the other has a mass of 37 a.m.u.

11. Relative Atomic Mass( R.A.M. ) This is the average mass of the isotopes – taking into consideration their abundance. It is usually not a whole number. Example Chlorine has a R.A.M. of 35.5 It has 2 isotopes one with a mass of 35 the other has a mass of 37. Therefore there must be more of the 35 isotope.