4.1.1.1 Atoms, elements and compounds

What makes up all substances?

All substances are made of atoms. An atom is the smallest part of an element that can exist

What are compounds?

Compounds are formed from elements by chemical reactions. Chemical reactions always involve the formation of one or more new substances, and often involve a detectable energy change. Compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed. Compounds can only be separated into elements by chemical reactions.

How do you write chemical equations?

Chemical reactions can be represented by word equations or equations using symbols and formulae.

H

Hydrogen

He

Helium

Li

Lithium

Be

Beryllium

B

Boron

C

Carbon

N

Nitrogen

O

Oxygen

F

Fluorine

Ne

Neon

Na

Sodium

Mg

Magnesium

Al

Aluminium

Si

Silicon

P

Phosphorus

S

Sulfur

Cl

Chlorine

Ar

Argon

K

Potassium

Ca

Calcium