Reactivity of a depends on how easily an electron(e-) can be removed. (This is lonization energy)

1. How is ionization energy related to how easily an electron can be lost from an atom? The easier it is to lose an electron the smaller the amount of energy needed to remove it (smaller ionization energy). ... The amount of positive charge increases as the number of protons increase from left to right across a period.

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.

the answer would be a