definitions

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Atomic number, Atomic structure and isotopes:

Atoms are what all elements are made of. All atoms consists of a nucleus, containing protons and neutrons, then they are surrounded by electrons that orbit the nucleus on shells.

Elements are a substance made up of one type of atom only.

Radioactive are when unstable atoms give off particles that can be harmful to humans.

Compounds are a substance formed by the chemical union of two or more elements.

Isotopes are atoms of an element with the same number of protons and electrons but a different amount of neutrons.

Mass is the amount of matter an object contains, in this case mass is measured in kilograms (kg).

Properties are the characteristic of something. Chemical properties include the reactions a sunstance can take part in. Physical properties include colour and boiling point.

Proton is a subatomic particle with a positive charge and a relative mass of 1.

Radioactive is when unstable atoms give of particles that can be harmful to humans.

Reactive is the tendency of a substance to undergo a chemical reaction.

Stable is when atoms are stable because their full outer shell contains the maximum amount of electrons.