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

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.

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.

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

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.

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.

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

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

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.).

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