The number of electrons equals the number of protons resulting in an elements neutral atom. This is due to electrons having a really small mass therefore not significantly contributing to the atomic mass. Pin On Useful Things For example boron B has an atomic number of 5 therefore it has 5 protons and 5. . Moreover since these two subatomic particles electrons and protons have opposite charges they cancel out and. To find the number of electrons an atom has start by looking up the element youre working with on the periodic table and locating its atomic number which will be in the upper left-hand corner of the square. For example hydrogen has just 1 electron in the s orbital of the first shell so its electron configuration notation is recorded as 1s1. With a mass of 0000549 amu electrons are negatively charged particles. Rules to Finding Number of Protons Neutrons and Electrons of protons atomic number of neutrons mass numb