Elements

Common elements

List of common elements Elements, compounds and mixtures Metallic and non-metallic elements
Elements in the Earth's crust Obtaining metals from their ores

There are about 100 elements in total, although only about 20 are in everyday use.

An element is the simplest of all chemical substances.

It is made up of only one kind of atom and cannot be decomposed.

A MOLECULE is formed when two or more atoms join together.

Two (or more) elements can combine together to form a compound.

A compound must be made of at least two elements chemically joined together.

magnesium + oxygen ----> magnesium oxide
(element) (element) (compound)

Table showing the common elements

Metallic Elements	Symbol
Aluminium	Al
Calcium	Ca
Copper	Cu
Iron	Fe
Gold	Au
Lead	Pb
Magnesium	Mg
Mercury	Hg
Potassium	K
Silver	Ag
Sodium	Na
Tin	Sn
Zinc	Zn

Non-metallic elements	Symbol
Bromine	Br
Carbon	C
Chlorine	Cl
Helium	He
Hydrogen	H
Iodine	I
Nitrogen	N
Oxygen	O
Phosphorus	P
Silicon	Si
Sulphur	S

Some common compounds
Carbon dioxide          C0₂
Copper oxide             CuO
Copper Sulphate        CuSO₄
Copper carbonate      CuCO₃
Magnesium oxide       MgO
Salt (sodium chloride) NaCl
Sulphur dioxide           SO₂
Water                         H₂O
Zinc oxide                   ZnO

Some differences between a metallic and non-metallic element:

Metal	Non-metal
Malleable	Brittle
Conducts electricity	Does not conduct electricity (except carbon, which does conduct)
High melting point (usually solid)	Low melting point (usually gas or liquid)
The oxides of a metal, when soluble, form an alkaline solution.	The oxides of a non-metalusually form an acidic solution.

Elements, Mixtures and Compounds: Summary

A substance is an element if it contains only a single kind of atom and can NEVER be decomposed.
eg copper, oxygen, carbon, iron, sulphur, zinc, gold

A substance is a compound if it contains more then one element chemically joined together.

eg water, magnesium oxide, copper sulphate, calcium carbonate, cobalt chloride, petrol

A mixture exists when there are at least two substances present (either elements, compounds or a combination of the two).

These two substances are not chemically joined and can often be easily separated.

eg air, ink, orange juice, wood, salty water

The main differences between a compound and mixture are summarized in the table below:

Mixture	Compound
A mixture contains two or more substances NOT chemically joined.	Contains at least two elements chemically joined together
The different substances may be visible and the appearance may not be uniform	Will look uniform in appearance (ie the same all the way through).
The substances can often be easily separated eg by filtration, evaporation, distillation, chromatography, using a magnet or a separating funnel.	The elements in a compound cannot be separated without a chemical change. ie a new substance will always be formed.
The substances can be mixed in any proportion.	The elements in a compound are always present in a fixed proportion.

Useful Links

Periodic Table of the Elements

This page is part of a site that uses frames.
If you cannot see navigation links to the left or top then click here to return to the start.