We want to find how much charge is on the electrons in a nickel coin. follow this method. a nickel coin has a mass of about 5.7 g.
a. find the number of atoms in a nickel coin. each mole (6.02 × 10^23 atoms) has a mass of about 57.9 g. answer in units of atoms.
b. find the number of electrons in the coin. each nickel atom has 28 electrons/atom. answer in units of electrons.
c. find the magnitude of the charge of all these electrons. answer in units of c.

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =

answerdmitry mendeleyev made a workable classification of the elements