Which of these values is most responsible for changing the boiling and freezing points of a solvent? ?

Colligative properties just including a solute changes the properties of the dissolvable, this is the reason we add salt to the streets in the winter time so the water won't solidify. The appropriate response is a number of the solute particles. 

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.