Exercises: Mass Spectra of Elements
A mass spectrum of a sample of neon shows three peaks, at mass-to-charge ratios of 20, 21, and 22. What does each peak represent, and what does the height of each peak…
A mass spectrum of a sample of neon shows three peaks, at mass-to-charge ratios of 20, 21, and 22. What does each peak represent, and what does the height of each peak tell you?
A mass spectrum of element X shows only two peaks: one at 10 with a relative abundance of 20%, and one at 11 with a relative abundance of 80%. Which isotope is more…
A mass spectrum of element X shows only two peaks: one at 10 with a relative abundance of 20%, and one at 11 with a relative abundance of 80%. Which isotope is more abundant? Would you expect the average atomic mass of X to be closer to 10 or to 11?
Chlorine has two naturally occurring isotopes, $^{35}\text{Cl}$ (75.77%) and $^{37}\text{Cl}$ (24.23%). Explain why the average atomic mass of chlorine on the periodic…
Chlorine has two naturally occurring isotopes, $^{35}\text{Cl}$ (75.77%) and $^{37}\text{Cl}$ (24.23%). Explain why the average atomic mass of chlorine on the periodic table is 35.45 and not a whole number.
Lithium has two isotopes: $^{6}\text{Li}$ with a mass of 6.015 u and $^{7}\text{Li}$ with a mass of 7.016 u. In a mass spectrum, the $^{6}\text{Li}$ peak has a relative…
Lithium has two isotopes: $^{6}\text{Li}$ with a mass of 6.015 u and $^{7}\text{Li}$ with a mass of 7.016 u. In a mass spectrum, the $^{6}\text{Li}$ peak has a relative abundance of 7.5% and the $^{7}\text{Li}$ peak has 92.5%. Calculate the average atomic mass of lithium to three decimal places.
Copper has two isotopes, $^{63}\text{Cu}$ (62.93 u) and $^{65}\text{Cu}$ (64.93 u). The average atomic mass of copper is 63.55 u. Determine the percent abundance of each…
Copper has two isotopes, $^{63}\text{Cu}$ (62.93 u) and $^{65}\text{Cu}$ (64.93 u). The average atomic mass of copper is 63.55 u. Determine the percent abundance of each isotope.
A student's mass spectrum of an element shows peaks at 24 (relative abundance 79.0), 25 (10.0), and 26 (11.0). Calculate the average atomic mass using the mass numbers…
A student's mass spectrum of an element shows peaks at 24 (relative abundance 79.0), 25 (10.0), and 26 (11.0). Calculate the average atomic mass using the mass numbers as the isotope masses, then identify the element.
Bromine exists as two isotopes of nearly equal abundance, $^{79}\text{Br}$ and $^{81}\text{Br}$. The mass spectrum of gaseous $\text{Br}2$ shows three peaks for the…
Bromine exists as two isotopes of nearly equal abundance, $^{79}\text{Br}$ and $^{81}\text{Br}$. The mass spectrum of gaseous $\text{Br}_2$ shows three peaks for the molecule. (a) Give the mass number of each molecular peak. (b) Predict the approximate relative heights of the three peaks, assuming the isotopes are 50.7% and 49.3% abundant, and justify your answer. (c) Explain why the spectrum of $\text{Br}_2$ differs from that of atomic bromine.
An element Z has three isotopes. The mass spectrum gives: $^{A}\text{Z}$ at 28.0 u, $^{B}\text{Z}$ at 29.0 u, and $^{C}\text{Z}$ at 30.0 u. The 28.0 u isotope is 90.0%…
An element Z has three isotopes. The mass spectrum gives: $^{A}\text{Z}$ at 28.0 u, $^{B}\text{Z}$ at 29.0 u, and $^{C}\text{Z}$ at 30.0 u. The 28.0 u isotope is 90.0% abundant, and the average atomic mass is 28.2 u. (a) Find the abundances of the other two isotopes. (b) Explain why the problem has a unique answer only because both the average mass and one abundance were given. (c) Describe how the spectrum would change if the sample were enriched in the heaviest isotope.