atomic structure & periodic table

Proton

Subatomic particle with a charge of +1 and a relative mass of 1.

Neutron

Subatomic particle with a charge of 0 and a relative mass of 1.

Electron

Subatomic particle with a charge of -1 and a relative mass of 1

Atomic Number

The number of protons in the nucleus of an atom.

Mass Number

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

Isotope

Atoms of the same element with the same number of protons but a different number of neutrons.

Relative Atomic Mass (Ar)

The average mass of an atom of an element compared to 1

Plum Pudding Model

An early model of the atom describing it as a ball of positive charge with negative electrons embedded in it.

Alpha Particle Scattering Experiment

An experiment by Rutherford that proved the mass of an atom is concentrated in a central, positively charged nucleus.

Bohr Model

The atomic model suggesting that electrons orbit the nucleus at specific distances in shells.

Chadwick

The scientist who discovered the neutron in the nucleus.

Group

A vertical column in the periodic table; elements in the same group have the same number of outer shell electrons.

Period

A horizontal row in the periodic table; elements in the same period have the same number of electron shells.

Mendeleev

The scientist who arranged the periodic table by atomic weight but left gaps for undiscovered elements.

Noble Gases (Group 0)

Unreactive non-metals with a full outer shell of electrons.

Alkali Metals (Group 1)

Highly reactive metals that get more reactive as you go down the group.

Halogens (Group 7)

Reactive non-metals that get less reactive as you go down the group and have higher melting points.