1. Atomic Structure
Structure of the atom
Elements
Mixtures
Compounds

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

3. 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

4. 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

5. 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.

6. 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

7. 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.

8. Exercise 3: Link the Definitions and Diagrams
Mixture
Compound
Element

9. 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

10. 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.

11. 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

12. 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)

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

14. 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.

15. 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

16. 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

17. 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