The element antimony exists in nature as two isotopes: 121Sb has a mass of 120.9038 u and 123Sb has a mass of 122.9042 u. The average atomic mass of antimony is 121.76 u. Calculate the relative abundance of the two antimony isotopes.

Gallium is a metal which forms compounds with a wide variety of uses. Some of the applications of gallium compounds include computer memory chips, light emitting diodes and lasers. Radioactive isotopes of gallium are used to image the human body and locate tumors. Naturally occurring gallium consists of two isotopes. One of those isotopes is 71Ga with an isotopic mass of 70.9247050 amu and an abundance of 39.892%. What is the mass number of the other isotope?

A 8.63 g sample of calcium sulfide was decomposed into its constituent elements, producing 4.80 g of calcium and 3.83 g of sulfur. Which of the statements are consistent with the law of constant composition (definite proportions)? The mass percentage of calcium plus the mass percentage of sulfur in every sample of calcium sulfide equals 100%. The mass ratio of Ca to S in every sample of calcium sulfide is 1.25. Every sample of calcium sulfide will be 55.6% by mass calcium. The mass ratio of S to Ca will vary based on how the sample was prepared. A different 8.63 g sample of calcium sulfide will contain a different amount of calcium.

Calculate the number of protons, neutrons, and electrons in 15 g of Si-28. The isotope Si-28 has a mass of 27.977 amu. 0.54 mol in 15 g 3.2×1023 atoms in 15 g protons = neutrons = electrons =

A hypothetical element, M, has four stable isotopes with the masses shown below. 109M = 108.9842 amu 107M = 106.9085 amu 105M = 104.9904 amu 103M = 102.9991 amu If the percentage abundance of 109M is 10.5%,  105M is 6.6% and the average atomic mass of M is 106.6785 amu, then what is the percentage abundance for 103M? Enter your answer as a percentage but without the % symbol. Use one decimal place.

A certain element has five stable isotopes with the following masses and percent abundance: Isotope 1:   63.929147 amu,   48.63% Isotope 2:   65.926037 amu,   27.90% Isotope 3:   66.927131 amu,    4.100% Isotope 4:   67.924848 amu,   18.75% Isotope 5:   69.925325 amu,     0.6200%      What is the atomic mass of this element? (Do not round intermediate calculations.)

A 8.95 g sample of calcium sulfide was decomposed into its constituent elements, producing 4.98 g of calcium and 3.97 g of sulfur. Which of the statements are consistent with the law of constant composition (definite proportions)? A. Every sample of calcium sulfide will have 55.6% mass of calcium B. The mass ratio of S to Ca in every sample of calcium sulfide is 0.80. C. Every sample of calcium sulfide will have 4.98 g of calcium. D. The ratio of calcium to sulfur will vary based on how the sample was prepared. E.