Which lists the elements in order from most conductive to least conductive? potassium (K), selenium (Se), germanium (Ge)
germanium (Ge), potassium (K), selenium (Se)
selenium (Se), germanium (Ge), potassium (K)
potassium (K), germanium (Ge), selenium (Se)

All the elements are arranged by melting points on the periodic table. in row they go from metals to gasses. in the row from sodium to argon, sodium is more reactive than the one on its right, magnesium.

The velocity would be 2 

In reversible reaction chemistry equilibrium is attained when the forward and reverse reactions are taking place at the same rate, thus, the concentrations of reactants and products remain the same. a reversible reaction is a chemical reaction where the reactants form products that, in turn, react together to give the reactants back. in irreversible reactions on the other hand, the reactants react to form the products, which cannot revert back into reactants.