CHEM1910: Transition Metal Compounds Overview

CHEM1910 - Introduction to Transition Metal Compounds Notes

Introduction

• Course: CHEM1910 with Dr. Nickeisha Stephenson

• Date: February 27th, 2024

• Topics: Transition metal properties, coordination complexes, oxidation states, ligands, and electron configurations.

Importance of Transition Metals

• Applications:

  • Therapeutic drugs

  • Coloring agents: used in paints and cosmetics

  • Biological molecules: Hemoglobin (oxygen transport) and chlorophyll (photosynthesis)

  • Gems: rubies, emeralds, garnets with applications in jewelry and technology.

• Notable Components: Heme and Chlorophyll structures, highlighting iron in heme.

Electron Configurations

• General Principle:

  • For first-row d-block elements, the 4s orbital is typically filled before the 3d level.

  • Higher energy levels lead to electrons being lost first during ion formation.

  • For example, $ext{V(0)}$ has the electronic configuration $[Ar]3d^5$.

• Cobalt Example:

  • Atomic number: 27

  • Neutral cobalt $ext{Co}$: $[Ar]3d^7 4s^2$

  • Cobalt(III) ion $ext{Co}^{3+}$: remove 3 electrons -> $[Ar]3d^6$

  • Cobalt(0) ion $ext{Co}^0$: primarily $[Ar]3d^9$.

Trends in Atomic Properties

• Across the d-block: Differences due to valence electron arrangements.

• Electron Repulsion: Weak, due to spatial distribution of d-orbitals

• Atomic Radii:

  • Generally decrease across main group elements due to increased effective nuclear charge.

  • Remain relatively stable across 1st row d-block elements due to d-electron shielding.

• Ionization Energies: Trends show gradual increase as electrons are added to the 3d orbital.

Ionization Energy Anomalies

• Notable anomalies occur from electron configuration changes during ionization processes (Fe, Mn).

• Mn2+ removal reduces electron-electron repulsions.

Electronegativity

• Describes an atom's ability to attract electrons in a bond.

• Trends:

  • Increase from left to right across a period due to effective nuclear charge predominance.

  • Increase down the group among d-block elements due to poor shielding in d-orbitals.

Oxidation States of d-block Elements

• Most transition metals exhibit multiple oxidation states due to gradual increases in ionization energies.

• Common states involve losing 4s and 3d electrons, with trends toward +2 states dominating in the 1st row d-block.

  • Scandium and Zinc are exceptions.

• Higher oxidation states exhibit greater reducing properties and more acidic oxides.

Coordination Chemistry

• Terms Explained: ligand, chelate, coordination number, complex ion, coordination sphere, Lewis acid/base, and denticity.

• Stereochemistry: Emphasize coordination numbers (CN) primarily being 2, 4, and 6, impacting the properties and reactivity of complexes.

Additional Observations

• Trends in density: Increasing from Scandium to Copper modularly with irregularities.

• Density of transition metals in period 6 enhances due to lanthanide contraction, compressing size without significant mass increase.

Conclusion

• Recognize patterns in oxidation states and chemical properties as they relate to electron configurations and underlying trends across the periodic table.