Question

Colour in transition metal compounds is attributed to (a) small size metal ions (b) absorption of light in uv region (c) complete ( \(\mathrm{n}, \mathrm{s}\) ) subshell (d) incomplete (n-1)d subshell

Short answer

(d) incomplete (n-1)d subshell

Step-by-step solution

Identify the Key Concept

Understand that the exercise is asking about the reason behind the color in transition metal compounds. The color occurs due to the electronic transitions within the metal ions.

Consider Option (a)

Evaluate the option of small size metal ions. While the size of the ion can influence properties, it's not the primary cause of color in transition metal compounds.

Consider Option (b)

Assess whether absorption of light in the UV region causes color. However, visible colors arise from absorption in the visible region, not the UV region, thus making this option incorrect.

Consider Option (c)

Review the option of a complete (n, s) subshell. In transition metals, the color is more commonly associated with the d subshell, not the s subshells.

Consider Option (d)

Evaluate the option of an incomplete (n-1)d subshell. This is the correct explanation because an incomplete d subshell allows d-d electron transitions, which absorb certain wavelengths of visible light and give compounds their color.

Select the Correct Option

Based on the analysis, select option (d) as it correctly identifies the incomplete (n-1)d subshell as the reason for the color in transition metal compounds.

Key concepts

Electronic Transitions

In chemistry, electronic transitions refer to the movement of electrons between different energy levels within an atom or molecule. Such transitions are significant because they can absorb light, leading to interesting optical properties like color. When an electron gains energy, it "jumps" from a lower energy level to a higher one, often by absorbing a photon of light. This phenomenon plays a critical role in explaining color in compounds, particularly in transition metals where such transitions involve electrons in visible light ranges. The absorbed light corresponds to specific wavelengths, causing the compound to exhibit the complementary color of the absorbed light. - This is why transition metal compounds can display a wide variety of colorful appearances. - Transition metals commonly involve electrons in their d-orbitals, contributing to their vivid colors.

d-d Electron Transitions

In transition metals, the color is primarily due to d-d electron transitions. These are special types of electronic transitions where an electron moves from one d-orbital to another within the same energy level. In transition metals, this occurs because their d orbitals are incompletely filled. The "d-d transitions" enable the absorption of light in the visible spectrum: - The energy difference between these d orbitals determines the wavelength of light absorbed. - Upon absorbing certain wavelengths, the remaining light is the color we observe. These transitions are subtle but crucial for the colors seen in transition metal compounds. It highlights the importance of the electron configuration in contributing to an element's optical properties.

Color in Chemistry

Color in chemistry often arises from interactions between light and matter, particularly via electronic transitions. The type of light absorbed or emitted by a compound greatly influences its color. Transition metal compounds are famous for their vivid colors due to the electron transitions chiefly involving their d-orbitals: - A compound’s perceived color is the wavelengths that are not absorbed, but reflected or transmitted. - This produces bright colors seen in gemstones, indicators, and more. In simple terms, the energy absorbed in electronic transitions dictates the color. For example, if a compound absorbs blue light, it will appear orange (the complementary color). Chemical context and factors like oxidation state and ligand environment can tweak the absorbed wavelengths, further diversifying possible colors.

Visible Light Absorption

Visible light absorption is integral to understanding why materials, especially transition metals, exhibit color. When an object absorbs certain wavelengths of visible light, the complementary colors manifest in what we see. In transition metal compounds, the incomplete d orbitals facilitate absorption in the visible range: - Wavelengths within 400 nm (violet) to 700 nm (red) are absorbed, while others are reflected or transmitted, producing color. - Transition metals' electronic structure specifically allows absorption of these wavelengths. The light not absorbed determines the observed color, making this concept vital for applications in dyes, pigments, and artwork. This principle is not just limited to transition metals but extends to organic and inorganic compounds, contributing to a material's aesthetic and functional properties.