Elementary charge the difference between the particle "electron" and the unit of charge "electron" was still blurred. Later, the name "electron" was assigned to the particle and the unit of charge "e" lost its name. However, the unit of energy electronvolt reminds us that the elementary charge was once called "electron". The maximum capacity of each pixel in a charge-coupled device image sensor, known as the "well depth", is typically given in units of electrons, commonly around 10 per pixel. In high-energy physics (HEP) Lorentz–Heaviside units are used, and the charge unit is a dependent one, formula_1, so that = 0.30282212088 .
Charge radius customary when charge radius takes an imaginary numbered value to report the negative valued square of the charge radius, rather than the charge radius itself, for a particle. The best known particle with a negative squared charge radius is the neutron. The heuristic explanation for why the squared charge radius of a neutron is negative, despite its overall neutral electric charge, is that this is the case because its negatively charged down quarks are, on average, located in the outer part of the neutron, while its positively charged up quark is, on average, located towards the center of the neutron.