1. The Chemical Earth (8.2.2)
Although most elements are found in combinations on Earth some elements are found uncombined.

2. Answers: 8.2.1 1.1 MgO, 1.2 AlCl3 1.3 K2SO4 2. Material Element/
Compound/
Mixture
Justification
Water
Compound
It is made up of two atoms of hydrogen and one of oxygen, chemically combined.
Sea water
Physically combination of salt and water, easy to separate.
Copper pipe
Element
It is a pure substance made up of one type of atom.
Oxygen
As in copper pipe above
Milk
Physical combination of water, fats, etc. Easily separated.
Smoke
Physical combination of air and unburned ash, hydrocarbons, etc. Easily separated
Petrol
Physical mixture of hydrocarbons easily separated by distillation.

3. Answers: 8.2.1
Chromatography has a stationery phase (paper, etc.) and a mobile phase (water, etc.). A mixture moves though the stationery phase by the liquid. Molecules “stick to” particles in the stationery phase, separating the mixture.
Compounds are harder to separate than mixtures because in a compound the atoms are linked by strong bonds between atoms. To separate the elements we must break the bond which normally requires large amounts of energy when compared to separating a mixture.

4. Chemical Reactivity
Chemical reactivity depends upon the electron structure of atoms.

5. The Periodic Table of Elements
Over many years the modern periodic table developed. It has a particular structure:
Groups – are the vertical columns. They indicate the number of electrons in the outermost shell of an atom.
Periods – are the horizontal rows. They indicate how many shells the element has.

6. The Periodic Table of Elements (contd.)
Boxes have a variety of information, but generally have: Name, Symbol, atomic number, and atomic weight.
Other information may include if the element is a solid, liquid, or gas at SLC (Standard Laboratory Condition), density, etc.

7. Classification of Elements
Elements are classified as:
Metal, Non-metals, or Semi-Metals
Metals – Are conductors of heat and electricity, malleable, ductile, have a metallic lustre.
Non-Metals – Are poor conductors of heat and electricity, are brittle and non-ductile normally do not have a lustre

8. Classification of Elements (contd.)
Semi-Metals (Metalloids) – exhibit some of the characteristics of both metals and non-metals. Silicon has a lustre, but is a poor conductor. Others are malleable or ductile and intermediate conductors.
Silicon Ingots
Tellurium
Germanium

9. Uses of Elements
Metals – many uses including: kitchen ware, building components, electrical components, jewellery, etc.
Non-metals – depending upon the non-metal: Sterilization (halogens), welding gases (argon, etc.).
Metalloids – many uses in semi-conductor industry (computer chips, etc.).

10. Questions
For the following elements, make a table to show how many electrons are in the outer most shell, and how many shells in total they have, their atomic symbol, atomic number, and atomic mass, and if they are metal, metalloid, or non metal:
Sulfur, Rhubidium, Selenium, Boron, Arsenic, Barium, Krypton, Germanium, Bromine
What are the uses of:
Chlorine, Sodium, Tungsten, Gold, Mercury, Zinc, Iron, Copper, Argon, Helium, Magnesium