Year 8 Science · Unit 2 · Lesson 09

History of the Atomic Model

Foundation Worksheet

Name

Date

Class

Learning Goals

Name the four main scientists who developed atomic models and match them to their contributions.
Sequence the key events in the history of the atomic model in the correct order.
Explain that models change because new evidence requires better explanations.

Warm Up

Match each term to its definition

Draw a line connecting each term on the left to its correct definition on the right. Or write the matching letter next to each term.

Term	Your answer	Definition
Dalton		A. A model where electrons orbit the nucleus in fixed energy levels, like planets around the Sun.
Thomson		B. The experiment that fired alpha particles at gold foil, revealing a dense central nucleus.
Rutherford		C. The model proposing that atoms are solid, indivisible spheres, like a billiard ball.
Bohr		D. A model with negative electrons spread throughout a ball of positive charge, like fruit in a pudding.
Gold foil experiment		E. The scientist who discovered electrons using a cathode ray tube in 1897.
Plum pudding model		F. The scientist who proposed the nuclear model after discovering the nucleus in 1911.

Order the steps

Number the events from 1 to 6 to show the correct order. Event 1 = what happened first.

Order	Event
	Rutherford fires alpha particles at a very thin sheet of gold foil (1911).
	Niels Bohr proposes that electrons orbit the nucleus in fixed energy shells (1913).
	J.J. Thomson discovers electrons using cathode ray tubes (1897).
	Rutherford discovers the nucleus and proposes the nuclear model of the atom.
	John Dalton proposes that atoms are solid, indivisible spheres (1803).
	Thomson proposes the plum pudding model, electrons embedded in a ball of positive charge.

1. Name the model proposed by J.J. Thomson and describe what it says about the structure of an atom.

Recall 2 marks

2. Why did scientists need to keep changing the atomic model? Use the word evidence in your answer.

Recall 2 marks

Wrap Up

In one sentence, what was the main idea of this lesson?