THANK YO If an individual proton has mass 1.007825 amu and an individual neutron has mass 1.008665 amu, and the observed atomic mass of gadolinium-157 is 156.92396 amu, what's its mass defect? Question 19 options: A) 1.38269 amu B) 1.35833 amu C) –1.35833 amu D) –1.38269 amu

1.38269 amu

Explanation:

Gadolinium-157 has 64 protons and 93 neutrons. Recall that mass defect his the difference between the calculated mass and the actual mass of the atom. This difference in calculated mass and actual mass exists because some mass is converted to the binding energy of the nucleus.

Mass of 64 protons= 64 × 1.007825 = 64.5008 amu

Mass of 93 neutrons= 93 × 1.008665 = 93.805845 amu

Mass of neutrons and protons= 64.5008 + 93.805845 = 158.306645 amu

Mass defect= 158.306645 - 156.92396 = 1.38269 amu

Therefore, mass's defect of gadolinium-157 is 1.38269 amu