Question

Give a brief account of the variation in properties of binary oxides of the first row \(d\) -block metals on going from Sc to Zn.

Short answer

Binary oxides of these metals generally decrease in oxidation state from Sc to Zn, show a transition from basic to amphoteric to acidic character, and exhibit varied structural, color, and magnetic properties.

Step-by-step solution

Understanding Binary Oxides

Binary oxides are compounds consisting of one element combined with oxygen. Here, we're examining the binary oxides formed by the first row of d-block metals from Scandium (Sc) to Zinc (Zn). Each metal forms oxides based on its common oxidation states.

Examining Oxidation States

The d-block metals exhibit a range of oxidation states. As we move from Sc to Zn, they generally decrease in oxidation number in their stable oxides (e.g., Sc forms Sc2O3 with +3 oxidation, Zn forms ZnO with +2 oxidation). The variability in oxidation states accounts for oxides with different metal-to-oxygen ratios.

Analyzing Basicity and Acidity

The oxides show a range of acid-base behavior. Early d-block metal oxides (Sc--Mn) are generally basic or amphoteric, reacting with acids and sometimes bases. Mid d-block metals (Fe--Cu) form amphoteric oxides, showing more complex behavior. Finally, later oxides tend to be more acidic, especially in higher oxidation states.

Understanding Structural Changes

The structure of these oxides can vary from ionic to covalent. For example, Sc2O3 is more ionic, while ZnO is covalent with a wurtzite or zincblende structure. These structural changes influence their electrical and mechanical properties.

Observing Trends in Color and Magnetic Properties

Many oxides show distinctive colors due to transitions of d electrons. Early oxides like TiO2 are white while others like MnO are colored. Magnetic properties also vary: some oxides (e.g. MnO, Fe2O3) exhibit magnetic behavior due to unpaired d electrons.

Key concepts

Oxidation States of d-Block Metals

As we explore the binary oxides of first-row d-block metals, understanding their oxidation states is crucial. D-block metals, from Scandium (Sc) to Zinc (Zn), exhibit a variety of oxidation states. This variability arises because these metals have d electrons that can be removed, leading to different stable oxidation states.
The general trend across the series is a decrease in oxidation state when forming stable oxides. For instance, Scandium typically forms an oxide with a +3 oxidation state, i.e., Sc extsubscript{2}O extsubscript{3}, while Zinc commonly forms ZnO with a +2 oxidation state. This decrease is associated with the filling of d-orbitals and is also influenced by the role these metals play in forming strong lattice energies in their respective oxides.
This fascinating ability to exhibit multiple oxidation states allows d-block metals to form a diverse range of oxides, each with unique chemical and physical characteristics.

Acid-Base Behavior of Metal Oxides

Binary oxides of d-block metals showcase a spectrum of acid-base behaviors depending on their position from Sc to Zn. Early d-block metals, such as Scandium and Titanium, form oxides that tend to be more basic or amphoteric.

• Basic oxides react readily with acids to form salts and water, such as when Sc extsubscript{2}O extsubscript{3} reacts with HCl.
• Amphoteric oxides like those of manganese can react with both acids and bases.

As you move further across the row towards Zinc, the oxides shift in behavior. Middle d-block metals like Iron, with its oxide Fe extsubscript{2}O extsubscript{3}, exhibit amphoteric properties, which means they can participate in both acidic and basic reactions. Towards the end of the series, the oxides become more acidic, especially as the oxidation state increases. Hence, Zinc oxide (ZnO) although sometimes amphoteric, has a tendency to display more acidic properties under certain conditions.

Structural Properties of Metal Oxides

When examining the structural properties of binary oxides of d-block metals, one notices the transition from ionic to covalent bonding. This shift is prominent as we move from Sc to Zn.
For example, Sc extsubscript{2}O extsubscript{3} typically forms a more ionic structure due to its metallic nature and larger ionic size. As we progress, structures like TiO extsubscript{2} and MnO show interesting arrangements, with TiO extsubscript{2} being quite covalent in nature. This is because of the strong metal-oxygen covalent interactions facilitated by overlapping d orbitals.
Furthermore, ZnO with either a wurtzite or zincblende structure is predominantly covalent. These structural changes are interconnected with electrical and mechanical properties and determine their utility in various industries, such as semiconductors, coatings, or catalysis.

Magnetic Properties of Metal Oxides

The magnetic properties of binary oxides of first-row d-block metals vary significantly due to the presence of unpaired d electrons.
Many of these oxides display distinctive colors and magnetic behaviors. Moving from Sc to Mn, you will find varying magnetic and chromatic characteristics, largely due to electronic transitions within the partly filled d orbitals.

• Oxides like MnO exhibit strong magnetic properties since manganese has unpaired d electrons that allow spin alignments, resulting in magnetic behavior.
• Fe extsubscript{2}O extsubscript{3}, another iron oxide, is a classic example of a ferromagnetic material due to the electron spin configurations within its structure.

On the other hand, Zinc oxide (ZnO) is not magnetic due to the lack of unpaired electrons in zinc's d orbitals. The variety in color and magnetic traits not only aids in the identification of these oxides but also in their application in areas like pigments, magnetic storage media, and electronic devices.