There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br₂ molecules, and the mass of a Br₂ molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of Br₂ consists of three peaks: Mass (u) Relative Size 157.836 0.2569 159.834 0.4999 161.832 0.2431 (d) Determine the average atomic mass of a bromine atom

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Step 1: Understand that the average atomic mass of an element is calculated by multiplying the mass of each isotope by its relative abundance, then summing these values. In this case, the relative abundance is given by the relative size of the peaks in the mass spectrum.

Step 2: Note that the mass of a Br2 molecule is the sum of the masses of the two bromine atoms in the molecule. Therefore, to find the mass of a single bromine atom, you need to divide the mass of the Br2 molecule by 2.

Step 3: Calculate the mass of a single bromine atom for each peak by dividing the mass of the Br2 molecule (given by the mass spectrum) by 2. This will give you the masses 78.918 u, 79.917 u, and 80.916 u.

Step 4: Multiply the mass of each isotope by its relative abundance (given by the relative size of the peaks in the mass spectrum). This will give you the contributions to the average atomic mass from each isotope.

Step 5: Sum the contributions from each isotope to find the average atomic mass of a bromine atom. This is the final answer.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses. For bromine, there are two stable isotopes: Br-79 and Br-81. Understanding isotopes is crucial for calculating average atomic mass, as the contribution of each isotope's mass and its relative abundance must be considered.

Mass Spectrum

A mass spectrum is a graphical representation of the mass-to-charge ratio of ions, which helps identify the different isotopes of an element and their relative abundances. In the case of bromine, the mass spectrum shows three peaks corresponding to the different isotopes of Br2, allowing for the determination of the average atomic mass based on their relative intensities.

Average Atomic Mass Calculation

The average atomic mass of an element is calculated by taking the weighted average of the masses of its isotopes, considering their relative abundances. This involves multiplying the mass of each isotope by its relative abundance (expressed as a fraction) and summing these products. For bromine, this calculation will yield the average atomic mass based on the data provided in the mass spectrum.

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Textbook Question

There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br₂ molecules, and the mass of a Br₂ molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of Br₂ consists of three peaks: Mass (u) Relative Size 157.836 0.2569 159.834 0.4999 161.832 0.2431 (a) What is the origin of each peak (of what isotopes does each consist)?

Textbook Question

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Textbook Question

There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br₂ molecules, and the mass of a Br2 molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of Br₂ consists of three peaks: Mass (u) Relative Size 157.836 0.2569 159.834 0.4999 161.832 0.2431 (c) Determine the average molecular mass of a Br₂molecule.

Textbook Question

There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br₂ molecules, and the mass of a Br₂ molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of Br₂ consists of three peaks: Mass (u) Relative Size 157.836 0.2569 159.834 0.4999 161.832 0.2431 (e) Calculate the abundances of the two isotopes. Calculate the abundance of the heavier isotope.

Textbook Question

It is common in mass spectrometry to assume that the mass of a cation is the same as that of its parent atom. (b) What percentage of the mass of an 1H atom does the electron represent?

Textbook Question

From the following list of elements—Mg, Li, Tl, Pb, Se, Cl, Xe, Si, C—pick the one that best fits each description. Use each element only once: (a) an alkali metal, (b) an alkaline earth metal, (c) a noble gas, (d) a halogen, (e) a metalloidin group 14, (f) a nonmetal listed in group 14, (g) a metal that forms a 3+ ion, (h) a nonmetal that forms a 2- ion, (i) an element that is used as radiation shielding.

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