chemical reactions

2. the species formed from chemical reactions.
3. a character, usually a letter or number, that's printed slightly below and to the side of another character
6. the composition or combination of parts or elements so as to form a whole.
9. reaction in which one element is substituted for another element in a compound, generating a new element and a new compound as products.
11. the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction.
12. occurs when pairs of electrons are shared by atoms.

1. a reaction in which a compound breaks down into two or more simpler substances.
4. a number placed in front of a chemical symbol or formula.
5. reaction occurs when parts of two ionic compounds are exchanged, making two new compounds.
7. is equal to 6.02214179×1023 atoms, or other elementary units such as molecules.
8. a substance that takes part in and undergoes change during a reaction.
10. the complete transfer of valence electron(s) between atoms.