What Are the Main Uses and Properties of Chromium?
Chromium is a chemical element with the atomic number 24. The word chromium has been derived from a Greek word ‘chroma’ which means colour. Chromium element has 24 protons and electrons and 28 neutrons. Chromium is a silver-grey metal that is lustrous and hard. It has an extremely high melting point.
In this article, we will explain the physical and chemical properties of chromium, the uses of chromium elements, and facts about chromium in detail.
Occurence and Symbol of Chromium
In the crust of the Earth, chromium is the 21st most prevalent element. Chromium compounds can be redistributed by volcanic eruptions and are found in the environment as a result of the erosion of chromium-containing rocks. Chromium is mostly found in chromite. This ore can be found in a variety of locations, including South Africa, India, Kazakhstan, and Turkey. It is not found in the free state in nature. The element chromium is represented as “Cr”. The atomic mass of chromium is 51.9961 amu.
The Element Chromium
Atomic Mass and Atomic Weight of Chromium
Atomic mass is the measure of the mass of a single atom or isotope. The average mass of an element in relation to all of its isotopes and their relative abundances is known as its atomic weight though the atomic mass and atomic weight of chromium is 51.996u.
Physical and Chemical Properties of Chromium
The physical and chemical properties of chromium are listed below:
Chromium is a lustrous steely-grey metal that is brittle and hard.
Chromium is solid at room temperature.
It is highly corrosion resistant.
When heated, it burns and forms green chromic oxide, which does not tarnish in air.
Chromium has a relatively low melting point of 1907 °C (3465 °F) when compared to the majority of transition metals.
Chromium has a boiling point of 4,840 °F (2,671 °C).
Uses of Chromium Element
Unalloyed chromium's high hardness and corrosion resistance make it a reliable metal for surface coating; it is still the most popular metal for sheet coating due to its above-average durability when compared to other coating metals.
A trace amount of chromium can be found in the crystal lattice structure of valuable gems such as emeralds.
Magnetic tape is produced using chromium (IV) oxide (CrO2).
Chrome plating, a thin layer of metal used for decoration and corrosion resistance, contains chromium.
Chromium is also used in metal ceramics.
Chromium is used as a catalyst.
Green, purple, red, and orange pigments made of chromium compounds are highly prized.
Glassware used in laboratories is cleaned with the substance chromic acid, which also eliminates all traces of organic material.
Biologically chromium helps in the breakdown of fats and carbohydrates. It promotes the production of cholesterol and fatty acids. They are crucial for the operation of the brain and other bodily processes. Chromium also aids in the metabolism of glucose and insulin.
Facts About Chromium
The element with the 21st highest abundance in the crust of the Earth is chromium.
Chinese ancestors used chromium.
The annual production of chromium is used to make metal alloys to an extent of about 80%.
The world's largest chromium producer is South Africa.
World wide production of chromium is about 20,000 tonnes.
85% of industrial use is made up of stainless steel and chrome plating (chromium electroplating).
Solved Questions
1. What is the biological importance of chromium?
Ans: Biologically chromium helps in the breakdown of fats and carbohydrates. It promotes the production of cholesterol and fatty acids. They are crucial for the operation of the brain and other bodily processes. Chromium also aids in the metabolism of glucose and insulin.
2. How many electrons, protons, and neutrons are present in chromium?
Ans: The atomic number of chromium is 24; thus, it has 24 protons and electrons and 28 neutrons.
3. Write a few properties of chromium.
Ans: The properties of chromium are listed below:
Chromium is a lustrous steely-grey metal that is brittle and hard.
Chromium is solid at room temperature.
Learning by Doing
Write true/false for the following.
South Africa is the largest producer of chromium in the world._________
World wide production of chromium is approx 30,000 tonnes._________
Chromium is liquid at room temperature._________
Summary
The first element in the periodic table's sixth column is chromium. It falls under the transition metal category. The most common isotope of chromium contains 28 neutrons in addition to its 24 protons and 24 electrons. Rarely does nature contain chromium as a free element. The majority of it is discovered in ores dispersed throughout the Earth's crust.
FAQs on Chromium: Key Facts, Uses, and Importance
1. What is chromium and what are its key chemical properties?
Chromium (symbol Cr, atomic number 24) is a hard, lustrous, steel-grey transition metal known for its high melting point and resistance to corrosion. A key property is its unique electronic configuration ([Ar] 3d⁵ 4s¹), which gives it a stable, half-filled d-orbital. It exhibits a wide range of oxidation states, with +3 and +6 being the most common and important in its chemistry.
2. What are the most common industrial applications of chromium?
Chromium's properties make it vital in several industries. Its primary applications include:
Alloying: It is the key ingredient in creating stainless steel, providing exceptional corrosion resistance.
Chrome Plating: Used to create a hard, shiny, and protective coating on car parts, tools, and fixtures through electroplating.
Pigments: Chromium compounds produce vibrant and stable colours, such as chrome yellow and chrome green, used in paints and dyes.
Catalysts: Certain chromium compounds are used as catalysts to speed up chemical reactions in industrial processes.
3. Why does chromium have an exceptional electronic configuration of [Ar] 3d⁵ 4s¹ instead of the expected [Ar] 3d⁴ 4s²?
Chromium deviates from the standard Aufbau principle to achieve a more stable electronic state. An atom gains extra stability when its orbitals are either exactly half-filled or completely filled. In the case of chromium, having a half-filled 3d orbital (3d⁵) and a half-filled 4s orbital (4s¹) results in a lower overall energy and greater stability compared to the expected configuration of 3d⁴ 4s². This stability arises from symmetrical electron distribution and higher exchange energy.
4. What are the different oxidation states of chromium, and why are +3 and +6 the most significant?
Chromium is a classic example of a transition metal with variable oxidation states, ranging from -2 to +6. The most significant and stable states are Cr(III) and Cr(VI). Cr³⁺ is the most stable form in aqueous solutions, forming many stable complexes. Cr(VI), found in compounds like dichromate (Cr₂O₇²⁻) and chromate (CrO₄²⁻), is a powerful oxidising agent and is widely used in chemical analysis and industrial synthesis, although it is also highly toxic.
5. How is chromium primarily found in nature and extracted for use?
Chromium is not found as a free metal in nature. Its principal commercial source is chromite ore, which has the chemical formula FeCr₂O₄. The extraction process typically involves crushing the ore and roasting it with sodium carbonate in the presence of air. This converts the chromium into sodium chromate, which is then treated further and reduced, often using carbon or aluminium, to produce pure chromium metal.
6. Why is hexavalent chromium (Cr(VI)) considered more toxic than trivalent chromium (Cr(III))?
The difference in toxicity is primarily due to their ability to cross biological membranes. Hexavalent chromium (Cr(VI)), being a strong oxidising agent with a structure similar to sulfate ions, can easily enter cells through anion transport channels. Once inside, it is reduced to Cr(III), generating reactive oxygen species that damage DNA, proteins, and lipids. In contrast, trivalent chromium (Cr(III)) is less mobile and cannot easily pass through cell membranes, making it significantly less toxic and even an essential trace element for human metabolism.
7. What is the importance of potassium dichromate (K₂Cr₂O₇) in chemistry?
Potassium dichromate is one of the most important chromium compounds, primarily valued for its role as a strong oxidising agent. In acidic solutions, the orange dichromate ion (Cr₂O₇²⁻) is reduced to the green chromium(III) ion (Cr³⁺). This property is extensively used in:
Volumetric Analysis: As a primary standard in redox titrations to determine the concentration of reducing agents like Fe²⁺ ions.
Organic Chemistry: For the oxidation of primary and secondary alcohols to aldehydes and ketones, respectively.
Breathalysers: In older breathalyser tests, it was used to detect ethanol, which would reduce the orange dichromate to green chromium(III).
