How many neutrons does element x have if its atomic number is 39 and its mass number is 84?

Which property is used to identify the origin of an igneous rock? color density hardness crystal size

Why do oceanic plates tend to subduction when colliding with a continental plate

The illustration shown is an ovum, a female sex cell. a mutation in this cell may be passed to the woman’s offspring during a) birth. b) mitosis. c) dna replication. d) sexual reproduction