Which of these elements is an alkaline earth metals? a. hafnium (hf) b. radon (rn) c. silicon (si) d. sulfur (s)

When light strikes a plane mirror, images form in locations where light does not actually reach. it only appears to the observer as though the light were coming from this position. what type of image is formed?

What determines the average kinetic energy of the particles in a gas? a. the number of collisions b. the number of particles c. the size of the particles d. the temperature

Me soon im confused much mass would a mole of hydrogen molecules contain? recall that hydrogen is diatomic. g/mol