[Chemistry Class Notes] on Chromium Pdf for Exam

What Is Chromium? 

The Chromium element has an atomic number 24 and is represented in the periodic table as the Cr element. It is the first element in group six. The chromium element is a very hard metal. It has a silver-grey appearance. The chromium electronic configuration is given as [Ar] 3d⁵ 4s¹. This logic behind the chromium electronic configuration is explained by the half-filled d orbital that is responsible for offering stability. The Cr electronic configuration is trivalent and is a very vital nutrient for the human body. This nutrient is found in different traces of human insulin, sugar, lipid metabolism, fatty acids and more. 

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A Few Common Chromium Properties

The atomic number of chromium (Z): 24

Group: group 6

Period: period 4

Block: d-block

Element category: Transition metal

Properties Of Chromium

The Chromium melting point is near about 2180 K ​(1907 °C)

Chromium boiling point: 2944 K ​(2671 °C, ​4840 °F)

Density: 7.19 g/cm3

The heat of fusion: 21.0 kJ/mol

The heat of vaporization: 347 kJ/mol

Uses Of Chromium

• Chromium is used in the stainless steel industry to manufacture and produce several alloys. A plating of chromium gives a mirror finish to stainless steel. Cars and trucks have number plates made up of stainless steel. These stainless steel parts contain chromium.

• Chromite is said to be the principal ore of Chromium. It is found in Africa, India, Turkey and Afghanistan. 

• Rubies get the bright red colour from chromium. Similarly, when treated with glass and emerald green colour is produced. 

• In the leather industry, the Cr element is used for tanning the leather products. But over the course of time, this process has proved to be highly toxic and as a result, an alternative process is being looked into. 

• Chromium when polished, shines like a mirror and reflects the toxic outline of the metal. 

• Various automobile decorations contain chromium or alloys made out of chromium. 

Symptoms Of Chromium Toxicity

Accuse exposure to chromium, in any form, leads to several diseases. These diseases are triggered along with symptoms such as nausea, vomiting, vertigo, fever and muscle cramps. The intensity of these symptoms can escalate and lead to more chronic symptoms such as renal failure, liver damage, respiratory tract discomfort and nephritis. Lung cancer is a very common disease linked with exposure to chromium. In addition to the lung, even the kidney and liver become a common target for chromium attacking particles. One should be extra careful while consuming chromium-rich food items. 

Chemical Properties Of Chromium 

1. Chromium Reacts with the Halogens: 

Chromium reacts with fluorine directly i.e F2 at 400°C and 200-300 atmospheric pressure to give chromium(VI) fluoride, CrF6.

Cr(s) + 3F2(g) → CrF6(s) [yellow]

Under milder conditions, chromium(V) fluoride, CrF5, is formed.

2Cr(s) + 5F2(g) → 2CrF5(s) [red]

In further milder conditions, Cr reacts with the halogens to give trihalide Chromium fluoride (III). 

2Cr(s) + 3F2(g) → 2CrF3(s) [green]

2Cr(s) + 3Cl2(g) → 2CrCl3(s) [reddish-violet]

2. Chromium Reacts with Acids: 

The Cr element dissolves in a dilute solution of hydrochloric acid to form solutions which contain the Cr(II) ion together along with H2 gas. Similarly while reacting with sulphuric acid the molecules become attack resilient. Chromium metal does not react with nitric acid or HNO3. 

Cr(s) + 2HCl(aq) → Cr2+(aq) + 2Cl–(aq) + H2(g)

3. Chromium Reacts with Sulphuric Acid: 

Chromium reacts with sulphuric acid to give chromium sulphate and hydrogen. The sulphuric acid must be a diluted solution. 

Cr + H2SO4 → CrSO4 + H2  

Fun Facts Related To The Chromium Element 

1. Chromium was first discovered in the year 1797 by a French Chemist named Louis Nicolas Vauquelin. 

2. The name means colour as the chromium element comes in different colours. Chromium, the word, has been derived from a Greek word “Chroma”. 

3. The Cr element is not found in free metal form. 

4. Each year about 20,000 tons of chromium is produced every year. 

5. The chromium electronic configuration gives the 4 natural isotopes. 

6. Stones of ruby and emerald contain traces of chromium. 

7. The most basic use of chromium is that it is used in the production of stainless steel. Chromium has anti-rusting properties which makes it suitable for being used in the production of stainless steel. Mostly all types of steel have a minimum chromium content of 10-11%. 

8. Considered to be the hardest metal present in nature, chromium is even stronger than iron, tungsten and titanium. In spite of this, the Cr element is very brittle. It can break into pieces and crumble easily if not handled properly.