Atomic Model

John Dalton

proposed atomic theory based on evidence, observation and experimentation

atomic theory

a theory that states that all matter is composed of tiny particles called atoms., all atoms of a given element are identical; atoms combine, separate and rearrange in chemical reactions; atoms combine is simple whole number ratiosw

Joseph John Thomson

discovered the electron

Ernest Rutherford

discovered the nucleus; gold foil experiment

Niels Bohr

discovered that electrons move around the nucleus in orbits called electron shells.

James Chadwick

Discovered the neutron

proton

positively charged particle

electron

negatively charged particle

neutron

no charge

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

neutral atom

same number of protons and electrons

ion

A charged atom

anion

An atom that has gained extra electrons; an atom with more electrons than protons

cation

An atom that has lost some of its electrons; an atom with more protons than electrons

isotope

Atoms of the same element that have different numbers of neutrons