Is the temperature at which a substance melts the same as the temperature changes from a liquid to a solid

No.

Explanation:

If the temperature changes a substance from it's original form, going from solid to liquid, then the temperature required to change it from a liquid to a solid are the opposite. For example, Ice is Water (H2O) in it's solid form. In order to freeze water into ice, the temperature must be very low. In order to melt the ice back into water, the temperature must be higher than the freezing point, but not too high or it will boil, making it a gaseous substance instead.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.