Which of the transition elements in the first transition series have anomalous electron configurations?

Name: Chemistry: A Molecular Approach
Author: Tro
ISBN: 9780134874371

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Understand that transition elements are those found in the d-block of the periodic table, specifically groups 3 to 12.

The first transition series includes elements from Scandium (Sc) to Zinc (Zn), with atomic numbers 21 to 30.

Recall that electron configurations are typically written by filling the lowest energy orbitals first, following the Aufbau principle, Hund's rule, and the Pauli exclusion principle.

Identify that anomalous electron configurations occur when electrons fill or half-fill d orbitals to achieve a more stable configuration, often seen in Chromium (Cr) and Copper (Cu) in the first transition series.

For Chromium, instead of the expected [Ar] 3d^4 4s^2, the configuration is [Ar] 3d^5 4s^1. For Copper, instead of [Ar] 3d^9 4s^2, the configuration is [Ar] 3d^10 4s^1. This is due to the extra stability associated with half-filled and fully filled d subshells.

Key Concepts

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

Transition Elements

Transition elements, or transition metals, are the d-block elements in the periodic table, characterized by their ability to form variable oxidation states and colored compounds. They include elements such as iron, copper, and nickel, which have partially filled d-orbitals. Understanding their electron configurations is crucial for predicting their chemical behavior and properties.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. For transition metals, this involves filling the 3d and 4s orbitals. Anomalous electron configurations occur when electrons are promoted from the s-orbital to the d-orbital to achieve greater stability, often seen in elements like chromium and copper.

Anomalous Electron Configurations

Anomalous electron configurations refer to deviations from the expected order of electron filling in atoms. In transition metals, this often results in a more stable arrangement by having half-filled or fully filled d-orbitals. For example, chromium (Cr) has an electron configuration of [Ar] 3d5 4s1 instead of the expected [Ar] 3d4 4s2, highlighting the importance of stability in electron arrangements.