Determine the mass defect of the nucleus of the oxygen atom 16 8O, which has a mass of 15.9949 amu. eat.

Neutron mass:
M (n) = 1.00866491560 a. eat.

Mass of hydrogen atom H1 (1 proton + 1 electron):
M (H1) = 1.00782503207 a. eat.

Mass of oxygen atom O16:
M (O16) = 15.99491461956 a. eat.

The oxygen atom consists of 8 protons, 8 neutrons and 8 electrons, that is, the mass of its constituent particles is equal to the mass of 8 neutrons and 8 hydrogen atoms H1:

M = 8 1.00866491560 + 8 1.00782503207 = 16.13191958 a. eat.

Subtracting the mass of the oxygen atom from this value, we obtain the mass defect:

D = 16.13191958 – 15.99491461956 = 0.137 a. eat.
Let’s calculate the error 0.137-0.004 = 0.133
answer: 0.133 amu

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