12. the number of protons and neutrons tells us:
| a. the principle quantum
number
b. the reactivity of the element e
c. the atomic mass
d. the atomic number
. both a and c

c. The atomic mass

Explanation:

The atomic mass is the total number of protons and neutrons which are present in the atomic nucleus of an element. All atomic nucleus have protons and neutrons except by exception of common form of hydrogen H+.

Mass number or atomic mass = proton number + neutrons number

so what is the problem with your lab report and whats the subject of the lab report? i will you

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.