2. Atoms & Elements

An element has two isotopes, X and Y, with mass numbers of 52.0 and 53.0 respectively. The relative atomic mass is 52.2. What is the percentage abundance of isotope X?

Antimony has two naturally occurring isotopes: Sb-121 with a mass of 120.904 amu and a natural abundance of 57.21%, and Sb-123. If the atomic mass of antimony is 121.760 amu, what is the mass of Sb-123?

Bromine has two naturally occurring isotopes, Br-79 and Br-81, with an atomic mass of 79.904 amu. Given that the mass of Br-81 is 80.9163 amu and its natural abundance is 49.31%, what is the mass and natural abundance of Br-79?

Copper has two isotopes. The Cu-63 isotope weighs 62.9296 amu and has 69.17% of the natural abundance. What is the atomic mass (in amu) of the second copper isotope if the average atomic mass of copper is 63.546 amu?

Gallium has an atomic mass of 69.723 amu. The Ga-69 isotope (68.926 amu) is 60.11% abundant. What is the mass (amu) of the other isotope?

Gallium has two naturally occurring isotopes: Ga-69 with a mass of 68.9256 amu and a natural abundance of 60.11%, and Ga-71. If the atomic mass of gallium is 69.723 amu, what is the mass of Ga-71?

A sample of chlorine weighing 20.57 grams contains two naturally occurring isotopes: Cl-35 and Cl-37. If the atomic masses are 34.9689 amu for Cl-35 and 36.9659 amu for Cl-37, and the natural abundance of Cl-35 is approximately 75.78%, what is the mass of Cl-35 in the sample?

Which formula is used to calculate the percentage abundance of an isotope in a sample?