1. Atomic Structure Structure of the atom Elements Mixtures Compounds

2. Structure of Atoms The atom was once thought to be the smallest particle you could get. We now know that atoms consist of three smaller particles. Neutron Proton Electron The protons and neutrons are found in the middle of the atom, this is called the nucleus. The electrons orbit around the outside of the nucleus. Lithium atom

3. The Differences between the Particles The protons and neutrons are roughly the same mass, but the electron has a mass that is negligible by comparison. The proton has a positive electrostatic charge. The electron has a negative electrostatic charge. The neutron has no charge, it is neutral. For a neutral atom there are always the same number of protons as electrons. Lithium has three protons, so it must have three electrons. ProtonNeutronElectron Charge Relative mass +1none 111/1840th

4. Elements, Mixtures and Compounds An ELEMENT is the simplest type of substance. A COMPOUND is when you have two or more different elements joined (bonded) together. A MOLECULE is when you have two or more atoms joined together (they may be the same element, they may not). A MIXTURE is when you have different elements or compounds together, but not chemically joined (bonded). You need to be able to interpret particle diagrams and deduce whether the diagram represents an element, a compound, a molecule or a mixture.

5. Compounds A compound is two or more elements joined together. Water is a compound made from the elements oxygen and hydrogen. What does a molecule of water look like? You know elements have symbols. In the same way we can represent compounds using a chemical formula which is a combination of the symbols of the elements from which it is made. This chemical formula tells you how many atoms of each element are present. WRONG! The chemical formula is H 2 O, this means that every molecule of water has two hydrogen atoms joined to one oxygen atom. Oxygen atom Hydrogen atom

6. Naming Compounds You can often use the chemical formula for a compound to deduce the name of the compound. (This does not always work though!) MgCl 2 - Magnesium chloride NaBr- Sodium bromide KI- Potassium Iodide Chlorine  chloride Bromine  bromide Iodine  iodide So, when the halogens form compounds, the ending –ine changes to –ide.

7. More Common Names for Compounds MgSO 4 …….. Magnesium sulphate NaNO 3 …….. Sodium nitrate CaCO 3 …….. Calcium carbonate KOH…….. Potassium Hydroxide …..(SO 4 )  Sulphates …..(NO 3 )  Nitrates …..(CO 3 )  Carbonates …..(OH)  Hydroxides