Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

1. A Review of General Chemistry

Atomic Structure

Organic Chemistry

1. A Review of General Chemistry

Atomic Structure

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3:35 minutes

Problem 4

Textbook Question

In the periodic table, the number 79.904 appears under the element bromine. What is the significance of this number?

Verified step by step guidance

The number 79.904 under the element bromine in the periodic table represents the atomic mass (also called atomic weight) of bromine.

Atomic mass is the weighted average of the masses of all the naturally occurring isotopes of an element, taking into account their relative abundances.

Bromine has two main isotopes: bromine-79 (with a mass of approximately 78.918 amu) and bromine-81 (with a mass of approximately 80.916 amu).

The atomic mass of bromine, 79.904, is calculated using the formula:

Atomic Mass = \sum (Isotope Mass \times Relative Abundance)

The value 79.904 is not a whole number because it reflects the average mass of bromine's isotopes, weighted by their natural abundances.

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Key Concepts

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

Atomic Mass

The number 79.904 represents the atomic mass of bromine, which is the weighted average mass of all the naturally occurring isotopes of bromine. Atomic mass is measured in atomic mass units (amu) and reflects both the number of protons and neutrons in an atom's nucleus, providing insight into the element's isotopic composition.

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, the two stable isotopes are bromine-79 and bromine-81, which contribute to the average atomic mass of 79.904 due to their relative abundances in nature.

Periodic Table

The periodic table organizes elements based on their atomic number, electron configuration, and recurring chemical properties. The atomic mass, such as 79.904 for bromine, is typically displayed below the element's symbol and provides essential information for understanding the element's behavior in chemical reactions and its physical properties.

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