do this sound correct bot

the coefficent is the number in front of the element or compound

Yes, that sentence is grammatically correct.

no but is that the correct sentence

Yes, the sentence is correct. "The coefficient is the number in front of the element or compound" is a proper statement that accurately describes the coefficient in a chemical equation.

finish this sentence below

blank are the tarting blank that react with each other to form new substances

"Reactants are the starting materials that react with each other to form new substances."

another word for materials

Another word for "materials" in this context is "substances."