Write out the electron configurations of the ions below and determine which one is listed with an incorrect charge. (the numbers and charges written after the elemental symbol should be understood as superscripts) A. I-
B. O2+
C. Al3+
D. Mg2+
E. none of the above

B

it must be O2- not O2+, because it's an anion not a cation.

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.