How many chlorine atoms are expected in the products of this chemical reaction? 2sb + 3cl2 ?

We expect 3 chlorine atoms per molecule of product produced.

Explanation:

Given the reactants 2 Sb + 3 Cl2. As you can see in periodic table, Cl always acts with an oxidation state of -1, while Sb can act with +3 or +5.  If reactants are balanced in the given part of the reaction, it means that the product must be 2SbCl3. In this reaction Sb has an oxidation state of +3.

Then 2 Sb + 3Cl2 ⇒ 2 SbCl3, so there are 3 atoms of chlorine per molecule of product produced.

If Sb was acting with +5, you need 5 atoms of chlorine per product and then

2Sb + 5Cl2 ⇒ 2SbCl5, this way you need more atoms than you have.