Answer:
2e⁻ are transferred in the formation of one formula unit of product
Explanation:
The reaction is:
2Rb + Br₂ → 2RbBr
In ground state, both elements have 0 as oxidation state.
In the RbBr, Rb acts with+1 and Br with -1.
Rb increased the oxidation state → Oxidation
Br decreased the oxidation state → Reduction
Rb → Rb⁺ + 1e⁻
Br₂ + 2e⁻ → 2Br⁻
Bromine had to gained 2 electrons, to decreased the oxidation state, so
(Rb → Rb⁺ + 1e⁻ ) ₓ2 = 2Rb → 2Rb⁺ + 2e⁻
(Br₂ + 2e⁻ → 2Br⁻) ₓ1 = Br₂ + 2e⁻ → 2Br⁻
2Rb + Br₂ + 2e⁻ → 2Br⁻ + 2Rb⁺ + 2e⁻
If we cancel the electrons, we reach the balanced reaction. In conclussion, 2 e⁻
