How the purity of a substance can be shown:
| Pure | Impure | |
| Melting Point | Sharp Melting Point; usually high | Range of temperatures |
| Boiling Point | Sharp Boiling Point; usually low | Range of temperatures |
| Chromatography | One well-defined Spot on chromatogram | Several spots on chromatogram |
Element – the simplest building blocks of the physical world. There are 92 naturally occurring elements. The periodic table is a list of elements in order of atomic number.
Atom – the defining structure of an atom which typically includes a nucleus of protons and neutrons with electrons orbiting the nucleus
Molecule – Two or more atoms joined together discreetly. (Usually non-metals; can be elements or compounds)
Compound – two or more elements (different types) chemically bonded. With compounds you can always give formula.
Mixture – two or more substances not chemically bonded
| Charge | Mass | |
| Proton | + | 1 |
| Electron | – | 0 |
| Neutron | NO CHARGE | 1 |
Ion – Charged particles that are formed when an atom loses or gains an electron Cat-ion – A positive ion
An-ion – A Negative ion
Valence Electrons – Electrons on the outer shell of an element
The Atomic Number is the number of Protons and Electrons unless it is an ion. (Protons = Electrons)
The Mass Number is the number of Protons + Number of Neutrons. To work out the number of neutrons you must calculate: Mass Number – Atomic Number = Number of Neutrons
Isotope – An element that occupies the same place in periodic table but has a different number of neutrons. The number of protons and electrons are the same.
Alloy – a mixture of a metal and another element (usually a metal)