Beryllium, magnesium and calcium all are located in the alkaline earth group. which of these characteristics do these elements have in common? a) they each have similar densities. b) they each have a similar melting point. c) they each form similar compounds when combined with oxygen. d) they each have their valence electrons in the same energy level.

Its (C) I guessed it and got it wrong just so I can give the answer away.

The answer should be vaporization 

1. why does the same side of the moon always face earthc.the rotational period of the moon is equal to one revolution around earth2. which is greater the moons period of rotation or its period of revolution  b.the moons revolution period around earth3.what was the major accomplishment of the apollo missions  d.landing on and exploring the moon4. which of these space missions involved the deployment of lunar rovers d.apollo5. which scientists are going to explore next on kepler-186fd. evidence of existence of life6.which mission is not going to explore the outside of the solar systemb.safir7.which technology limit the future of space exploration b. scientist must first develop certain technologies before missions can be completed.