Final answer:
The mass defect of fluorine-19 can be calculated by subtracting its actual atomic mass (18.9984 amu) from the sum of the masses of its individual protons, neutrons, and electrons, yielding a mass defect of 0.1593 amu.
Step-by-step explanation:
The mass defect of an isotope represents the difference between the sum of the masses of its protons, neutrons, and electrons and its actual atomic mass. To calculate the mass defect of fluorine-19 (19F), we must first determine the sum of the separate parts. A proton has an approximate mass of 1.0073 amu, a neutron has a mass of 1.0087 amu, and an electron has a negligible mass that can be approximated as 0.00055 amu.
Fluorine-19 has 9 protons, 10 neutrons, and 9 electrons. The combined mass will be:
(9 protons × 1.0073 amu) + (10 neutrons × 1.0087 amu) + (9 electrons × 0.00055 amu) = (9.0657 + 10.0870 + 0.00495) amu = 19.15765 amu.
Subtracting the actual mass of fluorine-19 given (18.9984 amu) from this sum provides the mass defect:
19.15765 amu - 18.9984 amu = 0.1593 amu.
Thus, the mass defect of fluorine-19 is 0.1593 amu to the fourth decimal place.