C1 Atomic structure (Combined)

element

A substance that is made up of only one type of atom and cannot be broken down chemically.

compound

A substance that is made of at least two different elements chemically bonded together.

molecule

Two or more atoms bonded together by covalent bonds.

formula

The chemical description of a substance using symbols from the periodic table showing the name and number of atoms of each element present.

plum pudding model

An early model of the atom

nuclear model

A refined model of the atom

nucleus

The small

electron

A negatively charged sub-atomic particle that orbits the nucleus of atoms. Charge -1

proton

A positively charged sub-atomic particle found in the nucleus of atoms. Charge +1

neutron

A neutral sub-atomic particle found in the nucleus of atoms. Charge 0

atomic number

The number of protons in an atom.

mass number

The number of protons + the number of neutrons in an atom.

isotopes

Atoms of the same element that have the same number of protons (atomic number) but different numbers of neutrons (mass number).

relative atomic mass

The average mass of all the different isotopes of an element in their relative proportions.

electron shell

A region of space around an atomic nucleus in which electrons are found. Also called energy levels.

electronic structure

A description of the way the electrons are arranged in a particular atom.

ion

An atom that has either lost electrons to become positively charged or gained electrons to become negatively charged.