Elements and compounds

Atom

Smallest part of an element

Element

A pure substance made of only one kind of atom

Compound

A substance made up of atoms of two or more different elements joined by chemical bonds

Mixture

A combination of two or more different substances that are not joined by chemical bonds

Chemical symbol

A one or two letter representation of an element

Number of elements

118

Chemical reaction

the formation of a new chemical substance

Periodic table

A chart of the elements showing the repeating pattern of their properties

Property

a description of a substance (e.g. soft/dense/shiny/reactive

Molecule

A group of atoms bonded together (can be the same type of atom, or different types of atom).

Separation of compounds

requires a chemical reaction to break the bonds between atoms.

Formula of an element

Has a single capital letter (e.g. O or Na)

Formula of a compound

Has more than one capital letter, and tells you the ratio of the elements in a compound. (e.g. CaO has a 1:1 ratio of calcium to oxygen)

Word equation

A way of writing out what happens in a chemical reaction using the names of the substances involved.

Symbol equation

A way of writing out what happens in a chemical reaction using the symbols that represent the substances involved.

Reactants

The substance(s) changed in a chemical reaction

Products

The new substance(s) formed in a chemical reaction