Question: estimate how many electrons there are in the human's body. assume the mass is 70 kg?
Answer: In summary, for a typical human of 70 kg, there are almost 7*10^27 atoms (that's a 7 followed by 27 zeros!) Another way of saying this is "seven billion billion billion." Of this, almost 2/3 is hydrogen , 1/4 is oxygen , and about 1/10 is carbon .