Who first suggested that matter is made of tiny, uncuttable particles?

• Leucippus and Democritus

• John Dalton

• J.J. Thomson

• Ernest Rutherford

How did early thinkers explain why iron was hard and clay was soft?

• Iron atoms were squishy, clay atoms were hard

• Iron atoms were soft and flexible, while clay atoms were hard and hooked

• Iron atoms were hard and hooked, while clay atoms were soft and flexible

• Both iron and clay atoms were squishy

Which scientist proposed the Law of Conservation of Mass?

• John Dalton

• J.J. Thomson

• Antoine Lavoisier

• Ernest Rutherford

Which scientist discovered negatively charged particles, later called electrons?

• Eugen Goldstein

• J.J. Thomson

• Ernest Rutherford

• John Dalton

What did Rutherford discover about the positive charge in an atom?

• It is spread out evenly throughout the atom.

• It is concentrated in a very small, central area.

• It is found in the electrons orbiting the atom.

• It does not exist in an atom.

What are the tiny positively charged particles that Rutherford discovered when he bombarded nitrogen with alpha particles?

• Electrons

• Neutrons

• Protons

• Alpha particles

How does the Bohr model represent electrons in an atom?

• As a cloud of probability around the nucleus.

• As particles spread throughout a positive pudding.

• In specific orbits around a central nucleus.

• As waves that can't be precisely located.

What does Heisenberg's theory say about knowing an electron's exact position and momentum at the same time?

• It is always possible to know both with certainty.

• It is impossible to know both with certainty.

• You can only know its position, not its momentum.

• You can only know its momentum, not its position.