Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

24. Transition Metals and Coordination Compounds

Electron Configurations of Transition Metals: Exceptions

General Chemistry

24. Transition Metals and Coordination Compounds

Electron Configurations of Transition Metals: Exceptions

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Problem 37a

Textbook Question

Specify the electron configuration for each of the following atoms and ions.

(a) Cr
(b) Cr3+

Verified step by step guidance

Step 1: Understand the electron configuration order.
The order of filling electron orbitals is based on the Aufbau principle, which follows the sequence: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p.

Step 2: Determine the electron configuration for Cr (Chromium).
Chromium has an atomic number of 24, which means it has 24 electrons. The expected electron configuration would be [Ar] 4s² 3d⁴, but due to electron stability, it is actually [Ar] 4s¹ 3d⁵.

Step 3: Explain the electron configuration anomaly for Cr.
Chromium is an exception to the typical filling order because having a half-filled d subshell (3d⁵) provides extra stability, so one electron from the 4s orbital is promoted to the 3d orbital.

Step 4: Determine the electron configuration for Cr³⁺ (Chromium ion).
To form Cr³⁺, three electrons are removed from the neutral chromium atom. Electrons are removed first from the outermost shell, which is the 4s orbital, followed by the 3d orbital. Therefore, remove two electrons from 4s and one from 3d.

Step 5: Write the electron configuration for Cr³⁺.
After removing three electrons, the electron configuration for Cr³⁺ becomes [Ar] 3d³.

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Key Concepts

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

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. It follows the Aufbau principle, which states that electrons fill the lowest energy orbitals first, and is typically represented using the notation of subshells (s, p, d, f) and their respective electron counts. Understanding electron configuration is essential for predicting an element's chemical properties and behavior.

Transition Metals

Transition metals, such as chromium (Cr), are elements found in the d-block of the periodic table. They are characterized by their ability to form variable oxidation states and complex ions due to the involvement of d electrons in bonding. The unique electron configurations of transition metals often lead to interesting chemical properties, including colored compounds and catalytic activity.

Ion Formation and Electron Loss

When atoms form ions, they can either gain or lose electrons to achieve a more stable electron configuration, often resembling that of the nearest noble gas. For example, chromium can lose three electrons to form the Cr3+ ion, resulting in a different electron configuration than its neutral state. Understanding how and why ions form is crucial for predicting the behavior of elements in chemical reactions.

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