If someone ask to loan them money and gives you each time a promisenary note to pay you back is that legal and binding

If you loan someone money and he doesn't pay  you as agreed, he is in breach of contract, promissory note or not.  The note serves as evidence to prove the contract and its terms.  However, it cannot be determined whether it is legally enforceable without knowing whether the debtor has any defenses to the contract (e.g. he may claim it was entered into under duress, that he was defrauded into entering it, that it is usurious, that he was not of legal age or mentally competent when he agreed to it, that you forgave the debt at some point etc. etc. etc.)  The better drafted the  promissory notes were (for example did they include merger clauses stating that they represented the entire agreement between the parties, superceded any previous oral or written agreements or representations, and couldn't be changed except in writing signed by both parties?), the better your chances of defeating any defenses.