Respuesta :
Mass Defect: 0.5505 amu.
Explanation
A nickel-60 atom contains sixty nucleons (neutrons and protons).
- Nickel has atomic number 28 as seen on a periodic table. 28 out of the 60 nucleons are thus protons.
- The rest of the 60 - 28 = 32 nucleons are, therefore, neutrons.
According to the question,
- each proton has a mass of 1.00728 amu. 28 of them shall have a mass of [tex]28 \times 1.00728 = 28.20384\; \text{amu}[/tex];
- each neutron has a mass of 1.00867 amu. 32 of them shall have a mass of [tex]32 \times 1.00867 = 32.27744 \; \text{amu}[/tex].
Mass of the 60 nucleons shall add up to [tex]28.20384 + 32.27744 = 60.48128 \; \text{amu}[/tex].
The mass defect of a nucleus is "the difference between the sum of masses of [its] components and [its] measured [mass]." ("Map: A Molecular Approach (Tro)", Chemistry Libretexts)
According to the question, the measured mass of a nickel-60 nucleus is 59.9308 amu.
The difference between the sum of the masses of its nucleon components and the mass of its nucleus is, therefore, [tex]60.48128 - 59.9308 = 0.5505\;\text{amu}[/tex] (accurate to four decimal places.)