How would you expect the number of vacancies per unit volume to change in a metal as the temperature increases? explain

 It will decrease

Explanation: The number of vacancies per unit volume in a metal when the temperature is increased will decrease because when temperature increases, it will increase the volume thereby decreasing the number of vacancies.

Vacancies are the holes which are created in the metal due to the absence of the metal ions from the crystal lattice. These are also known as holes or voids.

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.