An increase in temperature causes an increase in the pressure of a gas because there is an increase in the?

The forces holding naphthalene crystals together can be overcome when naphthalene is heated to a temperature of 354K resulting in the crystal to melting. These forces are known as?

A metallic ion X²⁺ with an inert gas structure contains 18 electrons. How many protons are there in this ion?

Which of the following physical properties decreases across the Periodic Table?

What are the possible oxidation numbers of an element if its atomic number is 17?