Question

multiple-choice questions

1. which statement best describes the contribution of j.j. thomson to atomic theory?

a. he proposed that atoms are indivisible and indestructible.
b. he discovered the nucleus at the center of the atom.
c. he discovered the electron and proposed the \plum pudding\ model.
d. he developed the quantum mechanical model of the atom.

1. what holds protons and neutrons together in the nucleus?

a. electromagnetic force
b. strong nuclear force
c. gravitational force
d. ionic attraction

1. in the modern quantum model, electrons are best described as:

a. fixed particles orbiting the nucleus in set paths
b. tiny solid spheres that cannot move
c. waves that exist in orbitals with probable locations
d. positive particles located in the nucleus

1. which of the following statements about isotopes is true?

a. isotopes have the same number of neutrons but different numbers of protons.
b. isotopes are atoms of different elements with identical masses.
c. isotopes have the same number of protons but different numbers of neutrons.
d. isotopes are unstable versions of all atoms.

1. which scientific tool allows scientists to directly observe or manipulate individual atoms?

a. particle accelerator
b. spectroscope
c. scanning tunneling microscope
d. mass spectrometer

Explanation:

1. J.J. Thomson discovered electrons and proposed the plum - pudding model. Option A was Dalton's idea. Rutherford discovered the nucleus (Option B). The quantum mechanical model was developed by others (Option D).
2. The strong nuclear force holds protons and neutrons together in the nucleus. Electromagnetic force (Option A) would cause protons to repel. Gravitational force (Option C) is too weak. Ionic attraction (Option D) is between ions, not in the nucleus.
3. In the modern quantum model, electrons are waves in orbitals with probable locations. Option A is the Bohr model. Option B is an old - fashioned view. Option D is incorrect as electrons are not positive.
4. Isotopes have the same number of protons (so same element) but different neutrons. Option A is wrong (same protons, different neutrons). Option B is wrong (same element). Option D is wrong (not all isotopes are unstable).
5. A scanning tunneling microscope can observe and manipulate individual atoms. A particle accelerator (Option A) collides particles. A spectroscope (Option B) analyzes light. A mass spectrometer (Option D) measures mass - to - charge ratio.

Answer:

1. C. He discovered the electron and proposed the "plum pudding" model.
2. B. Strong nuclear force
3. C. Waves that exist in orbitals with probable locations
4. C. Isotopes have the same number of protons but different numbers of neutrons.
5. C. Scanning tunneling microscope