Matter Revision set 2

In 1803 John Dalton suggested that all matter is made from atoms.

The electron was the first subatomic particle to be discovered by J.J. Thomson in 1897.

J.J. Thomson developed Dalton’s model to show the presence of electrons.

What was J.J. Thomson’s model called?

• Bohr model

• Particle model

• Planetary model

• Plum-pudding model

What did Rutherford suggest about the model of the atom?

• Atoms contain a nucleus.

• Atoms contain electrons.

• The atom is a solid sphere like a billiard ball.

• The nucleus is made up of protons and neutrons.

Around 1800, Dalton stated that atoms are the smallest particles that exist (diagram on far left).

The models show how the atomic model has developed further over time:
How and why was Dalton's model changed?

• HOW

  Solid positive sphere with small negative particles embedded in it.

  WHY

  Most of mass and positive charge must be in a small volume.

• HOW

  Small, heavy, positive nucleus with electrons orbiting in space around it.

  WHY

  Electrons must be in fixed orbits.

• HOW

  Positive nucleus with electrons in shells in space around it.

  WHY

  Atom must contain smaller particles.

• HOW

  Solid positive sphere with small negative particles embedded in it.

  WHY

  Atom must contain smaller particles.

Answer explanation

J.J. Thomson discovered electron (sub atomic particle_

The models show how the atomic model has developed further over time:
How and why was Thomson's model (2nd from left) changed?

• HOW

  Solid positive sphere with small negative particles embedded in it.

  WHY

  Most of mass and positive charge must be in a small volume.

• HOW

  Small, heavy, positive nucleus with electrons orbiting in space around it.

  WHY

  Electrons must be in fixed orbits.

• HOW

  Positive nucleus with electrons in shells in space around it.

  WHY

  Atom must contain smaller particles.

• HOW

  Small, heavy, positive nucleus with electrons orbiting in space around it.

  WHY

  Most of mass and positive charge must be in a small volume.

Answer explanation

Rutherford's alpha particle scattering experiment

The models show how the atomic model has developed further over time:
How and why was Rutherford's model (3rd from left) changed?

• HOW

  Solid positive sphere with small negative particles embedded in it.

  WHY

  Most of mass and positive charge must be in a small volume.

• HOW

  Small, heavy, positive nucleus with electrons orbiting in space around it.

  WHY

  Atoms must contain smaller particles

• HOW

  Positive nucleus with electrons in shells in space around it.

  WHY

  Electrons must be in fixed orbits.

• HOW

  Solid positive sphere with small negative particles embedded in it.

  WHY

  Most of mass and positive charge must be in a small volume.

Answer explanation

Bohr said that electrons had to be in fixed orbits to avoid spiralling into nucleus