Problem 41 - Chemistry and Chemical Reactivity

Question

A transition metal complex absorbs 425-nm light. What is its color? (a) red (c) yellow (b) green (d) blue

Step-by-Step Solution

Answer

Yellow (option c)

Step 1: Understand the Wavelength Absorption

The transition metal complex absorbs light at 425 nm. This wavelength of light falls in the violet range of the electromagnetic spectrum. When a substance absorbs a specific color, it will show the complementary color.

Step 2: Identify the Complementary Color

The color wheel shows that the complementary color of violet is yellow. Thus, if a substance absorbs violet light, the color that we see will be yellow.

Step 3: Conclude the Observed Color

Since the transition metal complex absorbs 425-nm light (violet), the color of the complex observed by the human eye is its complementary color, yellow.

Key Concepts

Wavelength Absorption

Transition metal complexes are fascinating because they can absorb light. This absorption is crucial because the colors we see depend on it. When a complex absorbs light at a specific wavelength, it means that wavelength is subtracted from the light that reaches our eyes. In the given exercise, the metal complex absorbs light at 425 nanometers.
This is part of the violet range in the spectrum of visible light. Remember, wavelength is a measure of the distance between two consecutive peaks in a wave. In terms of color, each wavelength corresponds to a different hue.

• Light absorption is about energy transfer.
• The wavelength absorbed affects the colors we see.
• This is a key property of transition metal complexes.

Electromagnetic Spectrum

The electromagnetic spectrum is a way to visualize all types of electromagnetic radiation. Visible light, which falls in this spectrum, is what our eyes can detect. The entire spectrum ranges from gamma rays, which have very short wavelengths, to radio waves, with very long wavelengths, but our focus is the visible part. Each color in visible light is associated with a range of wavelengths. For instance:

• Violet light ranges from about 380 to 450 nm.
• Blue light spans from approximately 450 to 495 nm.
• Green light is from around 495 to 570 nm.
• Yellow light falls between 570 and 590 nm.
• Orange light is between 590 and 620 nm.
• Red light spans from 620 to 750 nm.

Understanding where visible light fits into the electromagnetic spectrum helps us make sense of the absorption properties of materials and how they appear to our eyes.

Complementary Colors

When discussing color and light, complementary colors are crucial. The concept refers to pairs of colors that, when combined, cancel each other out, producing a grayscale color like white or black. For example, when a substance absorbs light of one color, the color we perceive is its complementary color. The color wheel is a helpful tool here. It shows us which colors are opposite each other. These pairs include:

• Violet and yellow
• Blue and orange
• Green and red

In our exercise, the transition metal complex absorbs violet light at 425 nm. Therefore, it appears yellow, which is opposite violet on the color wheel. This phenomenon is due to the way our eyes interpret the unabsorbed light.