The astronomical object known as crab nebula is thhe remnant of an exploded star. the explosion was seen by the chinese in 1054 c. e. however, the crab nebula is about 3500 ly distance from the earth in what year did the star actually explode.

What do the atoms of elements in the same group have in common? a. they have the same atomic numbers. b. they have the same average atomic masses. c. they have the same number of electron shells. d. they have the same number of electrons in their outermost shells.