electron mass = 9.10938188 × 10-31 kilograms = 0.000548579867 Atomic Mass units
The mass of an electron is atomic mass units is 5,485 799 090 70(16); the mass of the electron is not an atomic mass.
The electron has no atomic mass number. The mass of an electron is roughly 1/1800 of the mass of a proton or neutron.
If an atom looses an electron, neither the atomic mass nor atomic weight change appreciatively. If it looses a proton or neutron, both atomic mass and atomic weight decrease by one and it becomes an atom of a different element (on loss of a proton), or a different isotope of the same element (upon loss of a neutron).
Either a proton or neutron has an atomic mass of 1. An electron's mass is actually extremely small in comparison. The majority of the weight of an atom is in the nucleus.
Unified atomic mass unit
The electron configuration of beryllium is: 1s22s2. The atomic weight (not mass) of beryllium is 9,012 183(3).
The atomic weight of chlorine is 35,45.The atomic weight of chlorine is approximately 35.5 g/mol. An addition of electron is a negligible weight difference. Therefore, the mass is considered to remain the same at 35.5 grams per mole.
We are not using electron mass. We measure atomic mass by Mass of neutrons and protons.
Since the actual weight of an atom is extremely small, a more convenient way of designating the relative mass of the various atoms is the atomic weight. The atomic weight of an atom was originally defined as the sum of the number of its protons and its neutrons. Unfortunately, this idea proved not valid as exact measurements of the actual weights of the various elements and sub-atomic particles were made. The new definition of an atomic mass unit is that it is 1/12 of the atomic weight of Carbon-12. Most listing of elements include isotopes to display an average atomic weight.
1 over 1,836 AMUAnother answerIt's negligible. It has such a low amu that it is not a factor of the overall atomic mass of an atom
an electron is about 1/1836 amu.
When calculating the atomic mass of an atom, the mass of an electron is typically considered negligible. This is because the mass of an electron is almost 2000 times smaller than the mass of a proton or neutron, which are the primary components used in determining the atomic mass of an atom.