key concepts in chemistry

chemical formula

chemical formula

A combination of chemical symbols and numbers to represent a substance

chemical equation

A short, easy way to show a chemical reaction, using symbols.

reactants

A starting material in a chemical reaction

product

A substance produced in a chemical reaction

state symbols

solid (s), liquid (l), gas (g), and aqueous (aq)

aqueous

dissolved in water

ionic equations

shows only the particles that react and the products they form

hazard symbols

warnings printed on containers to indicate that either the container or the product is dangerous

oxidising

corrosive

toxic

highly flammable

harmful

enviromental hazard

John dalton

described atoms as a solid sphere

Plum pudding model

J.J Thomsons model of an atom, in which he thought electrons were randomly distributed within a positively charged cloud

nuclear model

Model of the atom with a nucleus containing protons and neutrons and with electrons in the space outside the nucleus

Bohr model

model of the atom in which electrons move rapidly around the nucleus in paths called cells

relative masses

Proton - 1

Neutron - 1

Electron - 0.0005

Relative charges of subatomic particles

Proton: +1

Neutron: 0

Electron: -1

mass number

the sum of the number of neutrons and protons in an atomic nucleus

atomic number

the number of protons in the nucleus of an atom

elements

A molecule composed of one kind of atom; cannot be broken into simpler units by chemical reactions.

isotopes

Atoms of the same element that have different numbers of neutrons and same number of protons

relative atomic mass

The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Mendeleev's periodic table

arranged by atomic mass and left gaps for undiscovered elements

modern periodic table

elements are arranged in order of increasing atomic number

group number

The number of electrons in the outer shell

period number

number of shells