For the reaction,

2 Cl(g) → Cl₂(g), what are the signs of and ?

In the reaction, chlorine molecule is being formed from chlorine atoms. Hence, bond formation takes place, leading to release of energy. As it is exothermic reaction, ∆H is negative (-ve).

In the reaction, 2 moles of atoms having higher randomness combine to form 1 mole of molecules, having lesser randomness.

Therefore, ∆S is negative (-ve ), which is represented as S_products – S_reactants.