Question

1. who discovered the first subatomic particle?

a. democritus. the atom
b. thomson. the proton
c. thomson. the electron
d. bohr. the electron

1. what part of the atom takes up all the volume?

a. electron cloud
b. protons
c. neutrons
d. solar system

1. what is the role of the proton as presented in this chemistry class?

a. power
b. stability
c. identity
d. space filling

1. which part of the atom contributes all of the mass?

a. weight
b. cloud
c. moles
d. nucleus

1. what is the role of the neutron as presented in this chemistry class?

a. power
b. stability
c. identity
d. balances out positive charge of the atom

1. the number 40.078 indicates______.

Explanation:

• Question 6: J. J. Thomson discovered the electron, the first - subatomic particle. Democritus proposed the concept of the atom but did not discover a subatomic particle. Bohr made contributions to atomic models but not the discovery of the first sub - atomic particle.
• Question 7: The electron cloud takes up most of the volume of an atom. Protons and neutrons are in the nucleus which is very small compared to the overall volume of the atom. The solar system is not part of an atom.
• Question 8: The number of protons in an atom determines its atomic number and thus its identity as a particular element.
• Question 9: The nucleus, which contains protons and neutrons, contributes almost all of the mass of an atom. Weight is a force related to mass and gravity, the electron cloud has very little mass, and moles are a unit of amount of substance, not a part of the atom that contributes mass.
• Question 10: Neutrons help to provide stability to the nucleus by counteracting the repulsive forces between protons.

Answer:

1. c. Thomson. The electron
2. a. Electron cloud
3. c. Identity
4. d. Nucleus
5. b. Stability