Atomic Structure: The Nuclear Model

Particulate nature of matter

Refers to the idea that all substances are made up of tiny, invisible particles.

Atom

The smallest particle of an element that still has the properties of that element.

Cathode ray

A stream of negatively charged particles called electrons.

James Chadwick

Discovered the neutron

Dalton's Atomic Theory

All matter is made up of very small particles called atoms. All atoms are indivisible and cannot be broken down into simpler particles.

William Crookes

Carried out experiments that involved passing an electric current through gases. Crookes showed that rays were coming from the cathode and cast a shadow of a Maltese cross. Called them cathode rays.

J.J Thompson discovery of electron

Passed cathode rays between uncharged plates and the rays passed straight down. Passed cathode rays between charged plates and the cathode rays deflected towards positive plate.

Robert Millikan

Oil drop experiment to measure exact charge of the electron.

Plum pudding model

An atom is a positively charged sphere which electrons are randomly embedded.

Rutherford Gold Foil Experiment

He fired positive alpha particles at thin gold foil. Most passed straight through meaning atom is mostly empty space. Some deflected at large angles meaning nucleus is small + positively charged. A few bounced back meaning nucleus is dense.

Electron cloud

Electrons are scattered around in space surrounding the nucleus.

Electron

A negatively charged sub-atomic particle found outside the nucleus.

Proton

A positively charged sub-atomic particle found in the nucleus.

Neutron

A neutral sub-atomic particle found in the nucleus.