Question

The gemstone emerald contains <1% Cr(III) substituted into the aluminum site of beryl, Be3Al2(SiO3)6. With reference...

The gemstone emerald contains <1% Cr(III) substituted into the aluminum site of
beryl, Be3Al2(SiO3)6. With reference to specific electronic transitions, account for its
vibrant green colour. Why does this colour differ so dramatically from that of ruby.

0 0
Add a comment Improve this question Transcribed image text
Answer #1

Ruby is an allochromatic mineral, which means its color arises from trace impurities. The color of an idiochromatic mineral arises from the essential components of the mineral. In some minerals the color arises from defects in the crystal structure. Such defects are called color centers.

The mineral beryl is a crystalline beryllium aluminosilicate with the chemical formula Be3Al2Si6O18. A pure crystal of beryl is colorless. However, if just 1% of the Al3+ ions are replaced with Cr3+ ions, the mineral becomes green in color and is known as emerald (Be3Al2Si6O18:Cr3+).

Because the energy of a photon of light is inversely proportional to its wavelength, the color of a complex depends on the magnitude of Δo, which depends on the structure of the complex. For example, the complex [Cr(NH3)6]3+ has strong-field ligands and a relatively large Δo. Consequently, it absorbs relatively high-energy photons, corresponding to blue-violet light, which gives it a yellow color. A related complex with weak-field ligands, the [Cr(H2O)6]3+ ion, absorbs lower-energy photons corresponding to the yellow-green portion of the visible spectrum, giving it a deep violet color.

even though both contain Cr3+ in an octahedral environment provided by six oxide ions. Although the chemical identity of the six ligands is the same in both cases, the Cr–O distances are different because the compositions of the host lattices are different (Al2O3 in rubies and Be3Al2Si6O18 in emeralds). In ruby, the Cr–O distances are relatively short because of the constraints of the host lattice, which increases the d orbital–ligand interactions and makes Δo relatively large. Consequently, rubies absorb green light and the transmitted or reflected light is red, which gives the gem its characteristic color. In emerald, the Cr–O distances are longer due to relatively large [Si6O18]12− silicate rings; this results in decreased d orbital–ligand interactions and a smaller Δo. Consequently, emeralds absorb light of a longer wavelength (red), which gives the gem its characteristic green color. It is clear that the environment of the transition-metal ion, which is determined by the host lattice, dramatically affects the spectroscopic properties of a metal ion.

Add a comment
Know the answer?
Add Answer to:
The gemstone emerald contains <1% Cr(III) substituted into the aluminum site of beryl, Be3Al2(SiO3)6. With reference...
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for? Ask your own homework help question. Our experts will answer your question WITHIN MINUTES for Free.
Similar Homework Help Questions
  • 3.2 Periodic trends 1. (0620-5 2012-Paper 1/2-Q21) Which properties of the element titanium, Ti, can be...

    3.2 Periodic trends 1. (0620-5 2012-Paper 1/2-Q21) Which properties of the element titanium, Ti, can be predicted from its position in the Periodic Table? forms coloured compounds conducts electricity when solid can be used has low density as a catalyst X A X X Xx 2. (0620-W 2012-Paper 1/1-Q20) The diagram shows an outline of the Periodic Table. U V W X Y Which of the elements U, V, W, X and Y would react together in the ratio of...

  • Using the Internet, find a recent case in the news about business fraud (within the last...

    Using the Internet, find a recent case in the news about business fraud (within the last 18 months) that involved systems and/or information breach. Summarize the situation, identify the control issues that were compromised and discuss what could have been done to mitigate the loss. Please refer to the six questions on page 143 related to Case 5-1. Adapt those questions to your case in the news and they will serve as good guidance for your paper. To understand the...

  • e. 18 Test Your Knowledge MULTIPLE CHOICE: Choose the one best answer. 1. Each element has...

    e. 18 Test Your Knowledge MULTIPLE CHOICE: Choose the one best answer. 1. Each element has its own characteristic atom in which a. the atomic mass is constant. b. the atomic number is constant. c. the mass number is constant. d. Two of the above are correct. e. All of the above are correct. 2. Which of the following is not a trace element in the human body? a. iodine b. zinc c. iron d. calcium e. fluorine 3. A...

  • Chapter overview 1. Reasons for international trade Resources reasons Economic reasons Other reasons 2. Difference between...

    Chapter overview 1. Reasons for international trade Resources reasons Economic reasons Other reasons 2. Difference between international trade and domestic trade More complex context More difficult and risky Higher management skills required 3. Basic concept s relating to international trade Visible trade & invisible trade Favorable trade & unfavorable trade General trade system & special trade system Volume of international trade & quantum of international trade Commodity composition of international trade Geographical composition of international trade Degree / ratio of...

  • What Exactly Does Being “Creative” and “Effective” Mean? An argument can be made that “effective” or...

    What Exactly Does Being “Creative” and “Effective” Mean? An argument can be made that “effective” or successful advertising is usually being creative with a purpose. Certainly, the notion of effective advertising can vary from culture to culture. In the United Kingdom, a premium may be placed on being different, humorous, or out-of-the ordinary in differentiating campaigns from the mass of mediocre advertising. In the United States, creative advertising is viewed more often as being “effective” in that the creativity has...

  • Need answers. thank you VOCABULARY BUILDER Misspelled Words Find the words below that are misspelled; circle...

    Need answers. thank you VOCABULARY BUILDER Misspelled Words Find the words below that are misspelled; circle them, and then correctly spell them in the spaces provided. Then fill in the blanks below with the correct vocabulary terms from the following list. amino acids digestion clectrolytes nutrients antioxident nutrition basal metabolic rate extracellulare oxydation calories fat-soluble presearvatives catalist glycogen processed foods cellulose homeostasis saturated fats major mineral coenzyeme trace minerals diaretics metabolism water-soluable 1. Artificial flavors, colors, and commonly added to...

  • 10. Write a one-page summary of the attached paper? INTRODUCTION Many problems can develop in activated...

    10. Write a one-page summary of the attached paper? INTRODUCTION Many problems can develop in activated sludge operation that adversely affect effluent quality with origins in the engineering, hydraulic and microbiological components of the process. The real "heart" of the activated sludge system is the development and maintenance of a mixed microbial culture (activated sludge) that treats wastewater and which can be managed. One definition of a wastewater treatment plant operator is a "bug farmer", one who controls the aeration...

ADVERTISEMENT
Free Homework Help App
Download From Google Play
Scan Your Homework
to Get Instant Free Answers
Need Online Homework Help?
Ask a Question
Get Answers For Free
Most questions answered within 3 hours.
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT