What is the subatomic particle used to define an element

Iron (3) oxide will decompose in the presence of hydrogen gas and heater to produced iron and digydrogen monoxide white a balanced chemical equation

Uranium can supply energy for the worlds electricity without admitting harmful greenhouse gases which of these statements best describes an outcome of uranium mining

Energy defines the different "states" of matter. in no more than 3 sentences, describe the amount of kinetic energy that each of the 3 states of matter possesses and relate that to the atom/molecular motion of each "state".