Electrons are capable of emitting energy in the form of light at very narrow ranges of wavelengths. these wavelengths can be measured to find the electron's
a. mass.
b. density.
c. energy level.
d. specific heat.

They can be used to determine the energy level.
This is because the energy of the light emitted will be the same as the difference between the energy level it was at before and after.

Ci think not

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