Why are electron volts used instead of Joules in Quantum Phenomena and how do you convert between the two?

In quantum and particle physics, quantities such as energy and momentum are extremely small and so it is logical to have a standard unit of energies at this scale. It saves time to write 1eV, as opposed to 1.6*(10^-19)J in every sum as well as making quantities easier to compare. An electron volt is described as the energy gained by an electron when passed through a charge of 1 volt and holds the quantity of 1.6*(10^-19)J. Note that this is numerically equivalent to the charge of an electron as E = qV. Therefore, to convert eV to Joules, you simply multiply by this number. To convert Joules to eV, you divide the energy by this constant.