Question

what determines the color of light that is emitted when an excited electron returns to ground state?
the amount of protons in the atom.
the amount of electrons in the atom.
the mass of the atom.
the energy of the excited electron

Explanation:

The color of light emitted when an excited electron returns to the ground - state is determined by the energy difference between the excited state and the ground state of the electron. Different energy differences correspond to different wavelengths (and thus colors) of light according to the formula $E = h
u=\frac{hc}{\lambda}$, where $E$ is energy, $h$ is Planck's constant, $
u$ is frequency, $c$ is the speed of light, and $\lambda$ is wavelength.

Answer:

The energy of the excited electron.