John Dalton publicized his atomic theory in the early 1800’s. Which part of his theory is NO longer valid?

A. All elements consist of tiny particles called atoms.
Incorrect. This is still true.

B. All atoms of a given element are identical.
Correct! Isotopes are atoms of the same element that have different masses.

C. All atoms of a given element are different than those of another element.
Incorrect. This is still true.

D. Atoms bond with other atoms to form compounds.
Incorrect. This is still true.

Which conclusion about the structure of the atom was a result of the “gold foil” experiment?

A. Atoms are composed of at least three types of subatomic particles.
Incorrect. The proton and the neutron were not discovered yet.

B. Atoms have negative particles called electrons.
Incorrect. This happened a few years before the gold foil experiment.

C. Atoms have negatively charged nucleus surrounded by mostly empty space.
Incorrect. The nucleus is positive, not negative.

D. Atoms are mostly empty space with a nucleus that is dense and positively charged.
Correct! Good job.

Which of the following shows the correct order of the development of the atomic theory?

A. 1. The atom is a solid sphere.
    2. The atom has electrons.
    3. The atom has a nucleus.
Correct! This shows correct historical development.

B. 1. The atom has electrons.
     2. The atom is a solid sphere.
     3. The atom has a nucleus.
Incorrect. If an atom has electrons it is not a solid.

C. 1. The atom has a nucleus.
     2. The atom has electrons.
     3. The atom is a solid sphere.
Incorrect. Electrons were discovered before the nucleus.

D. 1. The atom has a nucleus.
     2 . The atom is a solid sphere.
     3. The atom has electrons.
Incorrect. Electrons were discovered before the nucleus.

Which scientist below concluded, through experimentation with cathode rays, that atoms contain smaller particles called electrons?

A. Ernest Rutherford
Incorrect. Rutherford's experiment used gold foil.

B. Democritus
Incorrect. Democritus first proposed the idea of an atom.

C. John Dalton
Incorrect. John Dalton experimented with gases and chemical reactions.

D. J.J. Thomas
Correct! Thomson discovered the electron.

Which pair below correctly matches the scientist with their visual model of the atom?

1. Ernest Rutherford
   
2. Democritus
   
3. J.J. Thomas
   
4. John Dalton
   

A.
Correct!

B.
Incorrect. This is Thomas’s model.

C.
Incorrect. This is Democritus model.

D.
Incorrect. This is Rutherford model.