Plz help! :D

What element is as hard as magnesium?

Acontrol during an experiment. might change remains constant does not exist does change

Calculate the energy required to ionize a hydrogen atom to an excited state where the electron is initially in the n = 5 energy level. report your answer in kilojoules

Which statement correctly describes the phosphate ion, ? it is composed of one phosphorus atom and four oxygen atoms covalently bonded together, and there is a –3 charge distributed over the entire ion. it is composed of one phosphorus atom and four oxygen atoms covalently bonded together, and there is a –3 charge on the phosphorus atom. it is composed of one phosphorus atom and four oxygen atoms ionically bonded together, and there is a –3 charge distributed over the entire ion. it is composed of one phosphorus atom and four oxygen atoms ionically bonded together, and there is a –3 charge on the phosphorus atom.