Atoms form ions in order to become this ? metals nonmetal isotopes stable

When they lose electrons, they become positive and cations are positively charged ions. Nonmetals form anions bc they are closer to a full valence shell and they want to gain electrons. gain electrons-> become negative which makes them a negatively charged ion (a anion). A molecule is two or more atoms bonded together.

Why are positive and negative ions formed?

Remember that ions are formed only when electrons move from one atom to another; a proton never moves from one atom to another. Compounds formed from positive and negative ions are called ionic compounds. Individual atoms can gain or lose electrons. When they do, they become monatomic ions.

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.