Given the mass of an electron is (1/1836) amu, what percentage of the mass of a carbon-12 atom is contributed by its electrons?

The electrons contribute 0.027 23 % of the mass of a C-12 atom.

The percent by mass of a component is the percent of the total mass of the compound that is due to that component.

% by mass = (mass of component/total mass) × 100 %

Mass of 6 electrons = (6 electrons/1 atom) × ((1/1836 u)/1 electron) = 3.268 × 10⁻³ u.

Total mass of C-12 atom = 12 u

% by mass = mass of electrons/total mass × 100 % =

##(3.268 × 10⁻³ u)/(12 u) × 100 %## = 0.027 23 %