Chlorine atom? make up?

Question

what seems strange about the make up of the sub atomic particles in a chlorine atom Cl?

Answer 1

There are two common isotopes, 35Cl and 37Cl. It is not particularly strange or unusual but it might be described as such in a GCSE question.

Answer 2

Perhaps it is strange because it's mass number in most periodic tables is 35.5?

Which is derrived from averaging it's 2 isotopes :)

Answer 3

There are two Cl atoms which use up all their electrons in a double bond.  Don't know whats strange about that, but isn't all Chemistry strange?