Atomic structure and bonding

Element

Element

Contains one type of atom. Cannot be separated into anything simpler

Compound

Contains two or more element chemically combined. It is in fixed proportions and can only be broken done chemically eg H₂0

Mixture

Can be separated physically. Can be in any proportion

Atom

Smallest part of an element

Nucleus

Where protons and neutrons are tightly packed together. Positively charged

Shells

Where electrons are found orbiting the nucleus

Mass number

The number of protons and neutrons in the nucleus of an atom

Atomic number

The number of protons inside the nucleus of an atom

Isotopes

Different atoms of the same elements with the same number of protons and electrons but different numbers of neutrons in their nuclei

Relative atomic mass (Ar)

Mass of each atom of an element on a scale where 1 atom of 12C is exactly 12

Relative molecular mass (Mr)

Mass of each molecule on a scale where 1 atom of 12C is exactly 12

Relative formula mass

Mass of each formula unit on a scale where 1 atom of 12C is exactly 12

Ion

An atom or group of atoms that has an electrical charge, either positive or negative

Cation

An atom that loses electrons has more protons than electrons and has a positive overall charge

Anion

An atom that gains electrons has more electrons than protons so it has a negative overall charge

Ionic compound

Formed when electrons are transferred from a metal atom to a non metal atom during a reaction

Ionic bond

The electrostatic attraction between oppsitively charged ions

Ionic structure

Regular arrangements of ions held together by electeostatic attraction between oppsitively charged ions

Covalent bond

Sharing a pair of electrons between two atoms

Molecules

Two or more atoms covalently bonded together. They have no charge because they have an equal number of protons and electrons