Definitions

Element - is the simplest kind of substance that can exist on its own

Compound - is a substance made from 2 or more elements chemically combined

Atom - is the smallest particle that can exist on its own 

Molecule - is 2 or more atoms combined by covalent bonds

Ion - is a charged atom by losing or gaining electrons

Chemical symbol - is a letter of pair of leters used to represent an element

Empirical formula - is the smallest whole number ratio of atoms of each element in a compound

Chemical equation - is an equation showing the reactants and what they produce

Stoicheometry - is the ratio of moles

Isotope - is an element with the same atomic number but different mass numbers

relative isotopic mass - the mass of an isotope compared to 1twelth of carbon-12

relative atomic mass - the weighted mean mass of an atom compared to 1 twelth of carbon-12

metallic bonding - is the attraction between positive ions and delocalised electrons

covalent bond - is a shared pair of electrons between atoms

dative bond - is a shared pair of electrons between two atoms where one atom provides both of the electrons

electron pair repulsion theory - is when pairs of electrons repell each other to get as far a part around the central atom as possible but lone pairs repel more than bonding pairs and this is what makes up the shape of the molecule