periodictable

An element is a pure substance that cannot be broken down into simpler substances by chemical or physical methods. An element is a substance that is composed of only atoms of the same type of atom i.e. atoms with the same number of protons in their nuclei.

Only 92 elements occur naturally– number 1 is hydrogen, number 92 is uranium. About 24 ‘artificial’ elements have been produced in laboratories. The Elements are arranged in the Periodic Table, on page 44 of the Mathematics Tables. The elements are represented by symbols. The 1st 2 elements Hydrogen & Helium make up the most of the atoms in the universe. There are over 10 million different known pure substances.

Only 116 are elements; all the others are compounds. Like 26 letters in the Alphabet but millions of words!!!

Non-metallic Elements: Names, Symbols Note location of the non-metals in the Periodic Table (metal steps).

* Can show metallic properties

Property

State

Melting pt

Boiling pt

Colour

Density

Chrctrstc Test

Hydrogen (H)

Gas

-259°C

-253°C

Colourless

0.00089 g/cc

Burns with a ‘pop’

Oxygen (O)

Gas

-218°C

-183°C

Colourless

0.0014 g/cc

Relights a glowing splint

Water (H2O)

Liquid

0°C

100°C

Colourless

1 g/cc

blue cobalt chloride pink

The elements of a compound always occur in fixed ratio of mass. In water hydrogen is always one ninth of the total mass and oxygen is always eight ninths. The mass ratio of hydrogen to oxygen is always 1:8 in water.

About 80% of the elements are Metals. In the Periodic Table the metals are to the left of a zig-zag line formed by B, Si, As, Te and At.

Some Metallic Elements: Names, Symbols, Uses

Non-metals General Properties

1. Solid non-metals tend to be brittle – they are not malleable or ductile.

2. The solid non-metals tend to be dull – they are not lustrous.

3. Non-metals tend to be bad conductors of heat – good heat insulators.

4. Non-metals tend to be bad conductors of electricity – good electrical insulators.

5. Non-metals tend to gain electrons in chemical reactions becoming negative ions.

Almost half of the non-metals are gases: Helium, Neon, Argon , Krypton, Radon, Fluorine, Chlorine, Oxygen and Nitrogen. One non-metal is a liquid: Bromine. The other non-metals are solids: (At room Temperature)

Carbon – an Exceptional Non-metal

1. Graphite Carbon: it is a good conductor of electricity. Very soft.

2. Diamond Carbon: it is extremely hard.