Atomic Models

Question 1

What did the ancient Greeks believe particles were made of?

Answer 1

Invisible particles

Question 2

Why did the accepted models of the atom change over time?

Answer 2

Scientists conducted many experiments and had to take into account new experimental evidence into their models

Question 3

Explain how Rutherford showed that the ‘plum pudding model’ as wrong? (include methodology) [8]

Answer 3

Experiment:

• Alpha particles (AP) fired at thin sheet of gold
• Alpha particles are positively charged

What should have happened:

• most AP should be deflected very slightly due to positive pudding

What did happen:

• Most AP passed straight through
• small number deflected backwards strongly

Conclusions:

• tiny positively charged nucleus where mass is concentrated
• nucleus surrounded by cloud of freely orbitic negative electrons
• Atom mostly empty space