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Ch.2 - Atoms, Molecules & Ions
McMurry - Chemistry 8th Edition
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Tutti i libri di testoMcMurry 8th EditionCh.2 - Atoms, Molecules & IonsProblema 118
Capitolo 2, Problema 118

Naturally occurring boron consists of two isotopes: 10^B (19.9%) with an isotopic mass of 10.0129 and 11^B (80.1%) with an isotopic mass of 11.009 31. What is the atomic weight of boron? Check your answer by looking at a periodic table.

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1
Identify the isotopes of boron and their respective abundances and isotopic masses: 10^B with 19.9% abundance and isotopic mass of 10.0129, and 11^B with 80.1% abundance and isotopic mass of 11.00931.
Convert the percentage abundances into decimal form by dividing by 100: 19.9% becomes 0.199 and 80.1% becomes 0.801.
Calculate the contribution of each isotope to the atomic weight by multiplying the isotopic mass by its decimal abundance: for 10^B, multiply 10.0129 by 0.199; for 11^B, multiply 11.00931 by 0.801.
Add the contributions from each isotope to find the average atomic weight of boron.
Verify the calculated atomic weight by comparing it to the value listed on the periodic table.

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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 example, boron has two stable isotopes, 10^B and 11^B, which differ in their neutron count and thus their mass. Understanding isotopes is crucial for calculating the average atomic weight of an element based on its isotopic composition.
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Isotopes

Atomic Weight Calculation

The atomic weight of an element is calculated as the weighted average of the masses of its isotopes, taking into account their relative abundances. This involves multiplying the mass of each isotope by its percentage abundance (expressed as a fraction) and summing these values. For boron, the calculation would involve the isotopic masses of 10^B and 11^B, weighted by their respective natural abundances.
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Calculating Atomic Mass

Periodic Table

The periodic table is a tabular arrangement of chemical elements, organized by increasing atomic number and grouped by similar properties. It provides essential information, including the atomic weight of elements, which is often a decimal value reflecting the average of all isotopes. Checking the atomic weight of boron on the periodic table can confirm the accuracy of calculations made using isotopic data.
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Periodic Table Classifications
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