[a student]

hi my friend
I don't know how should I determine the number of spins for example I know that dotrium has I=1 or the spin number of 35Cl is 3/2 but I don't know how I should measure that.
I would be grateful if you help me

[sjb]

I assume you mean Deuterium? I don't think there is a way of determining spin numbers by rote, rather than just observing them - otherwise places like Wiki would not be littered with estimated spin numbers for the transuranics etc.

As to how you actually measure them, I guess things like ESR would help.