2. oxygen can combine with carbon to form two compounds, carbon monoxide, and carbon dioxide. the ratio of the masses of oxygen that combine with a given mass of carbon is 1: 2. this is an example of
a. law of mass conservation
b. law of definite proportion.
c. law of multiple proportions
d. none of the above

3. the smallest unit of an element that can exist either alone or in combination with other such particles of the same or different elements is the
.a. proton
c. electron
b. neutron
d. atom

7. an atom is electrically neutral because
a. thenumberof protons and neutrons are equal.
b. the number of protons and electrons is equal.
c. neutrons balance the protons and electrons.
d. it has the same number of protons, neutrons, and electrons.

8. what happens when an ion is formed?
a. the number of protons is changed.
b. the number of neutrons is changed.
c. the number of electrons is changed.
d. the number of proton, neutron, and electron is changed

bohr’s contribution to the development of atomic structures
a. referred to as the “plum pudding model.”
b. the discovery that electrons surround a dense nucleus.
c. proposed that electrons travel in circular orbits around the nucleus.
d. none of the above.