Atomic Structure Structure of the atom Elements Mixtures Compounds

What does an Atom Look Like? An atom consists of a nucleus surrounded by electrons.

The electrons orbit around the outside of the nucleus. 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. The protons and neutrons are found in the middle of the atom, this is called the nucleus. Neutron Proton Electron The electrons orbit around the outside of the nucleus. Lithium atom

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. Proton Neutron Electron Charge Relative mass +1 none -1 1 1 1/1840th

Exercise 1: Particles 1. Which three particles make up an atom? 2. Which two particles are found in the nucleus? 3. Which particle has no electrostatic charge? 4. Which particle has a negative charge? Neutron, proton and electron. Proton and neutron. The neutron. The electron.

Exercise 2: Atoms 1. Which letter represents the nucleus? 2. Which letter represents the electron? 3. Which particle has a positive charge? 4. How many protons has the atom shown? B A The proton Four A Beryllium atom B

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.

Exercise 3: Link the Definitions and Diagrams Mixture Compound Element

Exercise 4: Complete the Table 1. For the substances shown below, say which is a compound, which is a mixture and which is an element. Sand Rust Air Oxygen Sea water Salt Gold Steel Sulphur Helium Element Mixture Compound Oxygen Air Sand Gold Sea water Rust Sulphur Steel Salt Helium

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? Oxygen atom WRONG! Hydrogen atom 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. The chemical formula is H2O, this means that every molecule of water has two hydrogen atoms joined to one oxygen atom.

Exercise 5: What Elements? 1. For the compounds below, write down the names of the elements present. a) NH3 b) CH4 c) H2SO4 d) CaCl2 e) CO f) NaCl g) SiO2 h) Fe2O3 Nitrogen and hydrogen Carbon and hydrogen Hydrogen, sulphur and oxygen Calcium and chlorine Carbon and oxygen Sodium and chlorine Silicon and oxygen Iron and oxygen

Exercise 6: How Many? 1. For the compounds below, write down the names of the elements present and how many atoms of each there are. a) NH4OH b) C6H12O6 c) AlCl3 d) CO2 e) CuO f) HCl g) MgCl2 h) ZnCO3 Nitrogen(1), oxygen (1) and hydrogen(5) Carbon(6), hydrogen(12) and oxygen(6) Aluminium(1) and chlorine(3) Carbon(1) and oxygen(2) Copper(1) and oxygen(1) Hydrogen(1) and chlorine(1) Magnesium(1) and chlorine(2) Zinc(1), carbon(1) and oxygen(3)

Exercise 7: Draw the Structures 1. For the compounds below, draw the simple structures. a) NH3 b) CH4 c) CO2

So, when the halogens form compounds, the ending –ine changes to –ide. 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!) MgCl2 - 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.

Exercise 8: Naming Halides 1. For the compounds below, write down their names. a) ZnCl2 b) ZnBr2 c) MgBr2 d) CaCl2 e) NaI f) AgBr g) KCl Zinc chloride Zinc bromide Magnesium bromide Calcium chloride Sodium iodide Silver bromide Potassium chloride

More Common Names for Compounds MgSO4 …….. Magnesium sulphate NaNO3 …….. Sodium nitrate CaCO3 …….. Calcium carbonate KOH …….. Potassium Hydroxide …..(SO4)  Sulphates …..(NO3)  Nitrates …..(CO3)  Carbonates …..(OH)  Hydroxides

Exercise 9: Naming Compounds 1. For the compounds below, write down their names. a) Na2SO4 b) CaSO4 c) CuCO3 d) AgNO3 e) NaOH f) Ca(NO3)2 g) Mg(OH)2 Sodium sulphate Calcium sulphate Copper carbonate Silver nitrate Sodium hydroxide Calcium nitrate Magnesium hydroxide