At what temperature is the substance a heated gas ?

Option (c) is the correct answer.

Explanation:

Temperature at below zero degrees represent that the substance is in solid state.

Temperature at zero degree celsius represents that substance starts to melt.

Whereas temperature at 100 degree celsius represents that the substance is changing from liquid to gas.

On the other hand, temperature above 100 degree celsius represents that the  liquid has completely converted into gas.

Thus, we can conclude that above temperature is the substance a heated gas.

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.