Julius learns that adding protons to the nucleus of an atom changes its atomic number. Which of the following always occurs when the atomic number of an atom changes? A.
The color of the atom changes.
B.
The element represented by the atom changes.
C.
The properties of the atom stay the same.
D.
The atomic mass of the atom stays the same.

yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes

explanation:

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.