steph01 the first thing you need to think about is what is going on in your baby's head.
When you say he is being naughty what do you mean?
Do you mean he's touching something you don't want him to touch?
Do you mean he's throwing his food on the floor?
Do you mean hitting others?
Does he understand the effect of him doing these things?
These are all examples of behaviour which could be described as naughty when it is an older child doing it. We would assume that they knew these things were not acceptable and were choosing to ignore those rules.
At 10 months old your baby is not capable of understanding rules. He is exploring the world as he gets more mobile. He's experimenting with dropping things and seeing whether they reappear. He's working out how hard to hit or touch things by trial and error.
It is quite right to stop him doing something you don't want him to do by saying no and moving him away. This is the beginning of him learning right from wrong. He won't know why you are doing it for a while but you have to start somewhere.
Now if he is simply exploring the world around him why would you smack him? He doesn't know he is doing wrong so he won't know not to do wrong again. He will simply know that sometimes Mummy is kind to me but sometimes Mummy hurts me. He won't make links between his behaviour and your disapproval. He may however learn that, if he starts exploring, people hurt him and start choosing not to explore. That would be really sad.
As he gets older he will start to understand that the smacks have meaning but they will also make him frightened of you and teach him that smacking is a way to show your feelings. Are those things you want him to learn?
It is much better to use praise, distraction and consistent warnings of more appropriate consequences when he is old enough.
In the meantime just redirect his attention. Please don't smack.