The energy required to remove a valence electron from a gaseous atom or ion is called energy

Ionization potential

The energy required to remove an electron from a neutral isolated gaseous atom and convert it into a positively charged gaseous ion is called ionisation potential. It is also called ionisation energy. The electron to be removed is valence electron. It is most loosely bound electron. The ionisation potential corresponds to the process X (g) → X + (g) + e −

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.

1.43 x 10^-11 j the guy commented the awnser just making sure u see it .