Transition Metals: Electronic Configuration and Properties - SS3 Chemistry Lesson Note

Transition metals are a group of elements found in the d-block of the periodic table, occupying Groups 3 to 12. They are characterised by the filling of d-orbitals in their electron configuration and exhibit unique properties that distinguish them from other groups of elements. Let's explore the electronic configuration and properties of transition metals in detail:

Electronic Configuration: Transition metals have partially filled d-orbitals in their electron configuration, leading to their unique properties. The general electron configuration of transition metals is (n-1)d^(1-10) ns^(0-2), where n represents the principal quantum number of the outermost electron shell.

Variable Oxidation States: One of the defining characteristics of transition metals is their ability to exhibit multiple oxidation states (valency). This variability in oxidation states arises from the availability of d-orbitals for electron transfer during chemical reactions. Transition metals often form coordination complexes with ligands, and the ligands influence the metal's oxidation state.

Complex Formation: Transition metals readily form coordination complexes by coordinating with ligands (molecules or ions) through coordinate covalent bonds. These complexes can have distinct colours, which arise from electronic transitions within the d-orbitals of the metal ion.

High Melting and Boiling Points: Transition metals generally have high melting and boiling points compared to s-block and p-block elements. The presence of partially filled d-orbitals and the formation of metallic bonds contribute to the strength and stability of the metal lattice.

Malleability and Ductility: Like other metals, transition metals are malleable (can be hammered into thin sheets) and ductile (can be drawn into wires) due to their metallic bonding.

Good Conductors of Electricity and Heat: Transition metals are excellent conductors of electricity and heat due to the mobility of delocalized electrons in their metallic lattice.

Catalytic Activity: Many transition metals and their compounds exhibit excellent catalytic activity, serving as catalysts in various chemical reactions. The ability to change oxidation states and interact with reactants makes them effective catalysts.

Magnetic Properties: Some transition metals and their compounds display magnetic properties due to the presence of unpaired electrons in their d-orbitals. Ferromagnetism, paramagnetism, and antiferromagnetism are commonly observed magnetic behaviours in transition metal compounds.

Biological Importance: Transition metals play vital roles in biological systems as essential micronutrients and cofactors in enzymatic reactions. Examples include iron in haemoglobin (oxygen transport in the blood) and copper in cytochrome oxidase (cellular respiration).

Colour in Gemstones: Transition metals are responsible for the vibrant colours in many gemstones. For example, chromium imparts a red colour to rubies, and manganese contributes to the green colour of emeralds.

The unique properties of transition metals have significant implications in various scientific fields, such as materials science, catalysis, biochemistry, and electronics. Their versatility in oxidation states, complex formation, and catalytic activity makes them indispensable in numerous industrial applications, ranging from chemical synthesis to energy storage and conversion.