Use the periodic table to determine which of the following could be an isotope of bromine (Br). Check all that apply.

They are all decomposition reactions.

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf   

D=m/v =57.9/3 = 19.3 g/cm^3

The correct answer to this question is 28