The History of the Atom

19th century John Dalton

At the start of the ________ described atoms as solid spheres and said that different sphere made up the different elements.

Bohr

________ proposed that electrons orbit the nucleus in fixed shells and arent anywhere in between.

Ernest Rutherford

In 1909 ________ and his student Ernest Marden conducted the famous alpha particle scattering experiments.

Bohrs theory of atomic structure

________ was supported by many experiments and it helped to explain lots of other scientists observations at the time.

shell

Each ________ is a fixed distance from the nucleus.

Rutherford came up with an idea to explain his new evidence

the nuclear model of the atom

Plum pudding model

the atom is a ball of positive charge with electrons embedded in it

John Dalton model

atoms as solid spheres

who did plum pudding model

J J Thompson

Niel Bohr nuclear model

electrons orbit the nucleus in fixed shells and distances, and aren't anywhere in between

How did they discover the nuclear model

They fired positively charged alpha particles at an extremely thin sheet of gold

Nuclear model experiment finding

When alpha particles cam near the concentrated, positive charge of the nucleus, they were deflected. If they were fired directly at the nucleus,they were deflected backwards. Otherwise, they passed through the empty space

Nuclear model

a cloud of negative electrons surround the nucleus, and most of the atom is empty space. Electrons are randomly placed

Nuclear model inventors

Ernest Rutherford and Ernest Marsden

J J Thompson tests

his measurements of charge and mass showed an atom must contain even smaller, negatively charged particles, electrons

James Chadwick experiment

Provided evidence for neutral particles in the nucleus, called neutrons

Rutherford further discovery

Showed that the nucleus can be divided into smaller particles, which each have the same charge as a hydrogen nucleus, called protons

Order of discoveries

John Dalton - plum pudding model - nuclear model - bohr nuclear model - modern nuclear model

Order of discoveries names

John Dalton - J J Thompson - Ernest Rutherford - Niels Bohr - James Chadwick

Nucleus, shells and electrons relationship

Nucleus is in the centre of the atom and electrons orbit the nucleus in shells