The key difference between chromium and hexavalent chromium is that chromium is a chemical element whereas hexavalent chromium is any compound having chromium in its +6 oxidation state.
Chromium is a metal that is very useful in the production of alloys. The term hexavalent chromium refers to compounds containing chromium. The metal occurs in the +6 oxidation state. Thus, this means the hexavalent chromium compound has chromium atoms that have 6 electrons removed from the outermost orbitals.
CONTENTS
1. Overview and Key Difference
2. What is Chromium
3. What is Hexavalent Chromium
4. Side by Side Comparison – Chromium vs Hexavalent Chromium in Tabular Form
5. Summary
What is Chromium?
Chromium is a chemical element having atomic number 24. It is a metal having a silvery metallic appearance. Further, this element is the first chemical element of group 6 in the periodic table. We can categorize it as a transition metal; it is hard but brittle. It is important as the main additive for iron alloys such as stainless steel. Furthermore, the major characteristics that cause its high value are high corrosion resistance and hardness. Some chemical properties of chromium are as follows:
• The symbol is Cr.
• A d-block element
• Electron configuration is [Ar]3d54s1
• Exists in the solid phase at standard temperature and pressure
• Melting point is 1907 °C
• Boiling point is 2671 °C
• Density is about seven times more than the density of water
• The common oxidation states are +3 and +6
• A strong oxidizing agent compared to molybdenum and tungsten oxides
Figure 01: Chrome Yellow
Some important physical properties are as follows:
• Extremely hard
• Can scratch samples of quartz due to high hardness
• High resistance towards tarnishing
• Unusually high specular reflection
• Antiferromagnetic ordering at room temperature (above 38 °C it is paramagnetic)
• Undergo passivation by oxidation when the metal is exposed to normal air
When considering the uses of chromium, it is an important component in stainless steel, useful for surface coating purposes, as yellow pigments, chromium oxides as green pigments, preservation of wood (chromium +6 salts), etc.
What is Hexavalent Chromium?
Hexavalent chromium is any compound containing chromium in the +6 oxidation state. Usually, we get the hexavalent form of chromium from the chromium ore. But, there are other hexavalent compounds as well, such as chromium trioxide.
Figure 2: Chromium Trioxide
Furthermore, these compounds are important in the textile industry as dyes, important for wood preservation, as components in anti-corrosion products, components in paints, etc. However, these hexavalent compounds are toxic and considered as human carcinogens. It is because the structure of hexavalent chromium is similar to the sulfate; thus, it easily transports into cells via sulfate channels.
What is the Difference Between Chromium and Hexavalent Chromium?
Chromium is a chemical element having atomic number 24. The key difference between chromium and hexavalent chromium is that chromium is a chemical element whereas hexavalent chromium is any compound having chromium in its +6 oxidation state.
Moreover, we can symbolize chromium as Cr, but the symbol for hexavalent chromium is Cr(VI) or chromium-6. Chromium can exist in different oxidation states, but the most stable and common states are +3 and +6. But, in hexavalent compounds, the chromium is essentially in the +6 oxidation state.
Summary – Chromium vs Hexavalent Chromium
Chromium is a chemical element having atomic number 24. The key difference between chromium and hexavalent chromium is that chromium is a chemical element whereas hexavalent chromium is any compound having chromium in its +6 oxidation state.
Reference:
1. West, Larry. “What Is Chromium-6?” ThoughtCo, Mar. 4, 2019, Available here.
Image Courtesy:
1. “Laidlaw school bus” (Public Domain) via Commons Wikimedia
2. “Chrom(VI)-oxid” By BXXXD – Own work (CC BY-SA 3.0) via Commons Wikimedia