Unit 1: 2.5: Atomic Masses Flashcards
A relative scale of masses based on the mass of carbon-12 being the standard and having a mass defined as exactly 12 u.
atomic mass scale
A mass equal to one-twelfth of the mass of a carbon-12 atom; also abbreviated as amu.
atomic mass units, u
The weighted average of the masses of the naturally occurring mixture of isotopes of an element, compared with one-twelfth of the mass of a carbon-12 atom.
atomic mass
The average taking into account the relative numbers of atoms of each type of isotope.
weighted average
Naturally occurring copper consists of 69.17% Cu-63, which has an isotope mass of 62.9396u and 30.83% Cu-65, which has an isotope mass of 64.92.78u. What is the atomic mass of copper?
63.55u
Naturally occurring potassium consists of the following isotopes in the percentages listed:
K-39: 38.9637u (93.258%)
K-40: 39.9640u (0.0117%)
K-41: 40.9618u (6.7302%)
What is the atomic mass of potassium?
Atomic mass= 39.0983u
The most abundance naturally occurring isotope of chlorine is Cl-35, which has an isotope mass of 34.9689u. Its natural abundance is 75.76%, and Cl-37 is the only other chlorine isotope that has a measurable abundance. Given that has a measurable abundance. Given that the atomic mass of chlorine is 25.435u, calculate the isotope mass and abundance of Cl-37.
Cl-37 mass= 26.97u
The most abundance naturally occurring isotope of boron is B-11, which has an isotope mass of 11.0093u. Its natural abundance is 80.1%, and B-10 is the only other boron isotope that has a measurable abundance. Given that the atomic mass of boron is 10.811u, calculate the isotope mass and abundance of B-11.
B-10 mass= 10.0u
Which of these is the most reasonable value for the isotope mass of bromine-79?
a. 35u
6. 79u
c. 79.904u
d. 78.918u
b
For a given element or isotope, which of these would have a different value on another planet?
a. atomic number
b. mass number
c. isotope mass
d. atomic mass
d
