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Question
Give a reason for the following:
The mass number of an atom is slightly less than the actual atomic mass.
Solution
Atomic mass = number of protons + number of neutrons + number electrons, and mass number = protons + neutrons
∴ Atomic mass = mass number + mass of electrons
Though the mass of electrons is very small 1/1837 of the hydrogen atom, yet the mass of electrons is there.
∴ Mass number is slightly less than the atomic mass.
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