With two questions about radium
1. what is radium position on the periodic table including a list of other elements that have similiar properties
2. five compounds that radium can form (and identify if each compound is naturally occuring, human made, or both)

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.

i'm assuming that it's c.) red bank..