An atom has atomic number 5 and mass number 11. how many neutrons does the atom have?
5
6
10
11

6

Simple hack to remember: Subtract the atomic number from the mass number to find the number of neutrons.

120,630,890

step-by-step explanation:

110+10=120,620+10=630,880+10=890

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.