Arsenic Metal, 7440-38-2

Arsenic Metal, 7440-38-2

Arsenic Metal is a metalloid element represented by the symbol "As" on the periodic table, with an atomic number of 33. It exhibits both metallic and non-metallic properties. Arsenic is commonly found in nature as compounds and is rare in its pure form. Below are the technical, physical, and chemical properties, applications, and other details about arsenic metal:

Technical Properties:

• Symbol: As

• Atomic Number: 33

• Atomic Weight: 74.922

• CAS Number: 7440-38-2

• Crystal Structure: Rhombohedral (metallic arsenic) and amorphous (yellow arsenic).

• Classification: Metalloid (exhibits both metal and non-metal properties).

Physical Properties:

• Color: Metallic arsenic is gray, while yellow arsenic is yellow.

• Density: 5.727 g/cm³ (metallic arsenic).

• Melting Point: 817°C (sublimes at 817°C, transitioning directly from solid to gas).

• Boiling Point: 614°C (no boiling point due to sublimation).

• Hardness: Approximately 3.5 on the Mohs hardness scale.

Chemical Properties:

• Reactivity: Stable in air and water at room temperature but forms toxic compounds like arsenic trioxide (As₂O₃) when heated.

• Reaction with Acids and Bases: Insoluble in dilute acids but dissolves in strong oxidizing acids like nitric acid.

• Compounds: Forms compounds such as arsenic trioxide (As₂O₃), arsenic pentoxide (As₂O₅), and arsenic sulfide (As₂S₃).

• Toxicity: Arsenic and its compounds are highly toxic, posing significant risks to human health and the environment.

Applications:

1. Semiconductor Industry:

   • Compounds like gallium arsenide (GaAs) are used in semiconductors and LEDs.

2. Wood Preservation:

   • Copper, chromium, and arsenic compounds (CCA) were used to protect wood from insects and fungi (now restricted in many countries).

3. Pesticides:

   • Historically used as insecticides and herbicides in agriculture (now limited due to toxicity).

4. Glass Industry:

   • Used for coloring and opacifying glass.

5. Metallurgy:

   • Used to harden lead and copper alloys.

6. Medical Applications:

   • Historically used in some medicines, but its use is now highly restricted due to toxicity.

Other Names:

• Arsenic (English)

• Metallic Arsenic

• As (Chemical Symbol)

Common Names in Everyday Language:

• Arsenic is commonly known as "poison" in everyday language. Arsenic trioxide (As₂O₃), in particular, has been used as a poison throughout history.

Why Should It Be Preferred?

1. Semiconductor Properties:

   • Compounds like gallium arsenide (GaAs) are used in high-performance electronic devices.

2. Wood Preservation:

   • Enhances the durability of wood (though its use has declined due to environmental concerns).

3. Glass and Ceramic Industry:

   • Effective for coloring and opacifying glass.

Environmental and Health Impacts:

• Environment: Arsenic can cause soil and water pollution. Mining and industrial waste are major sources of arsenic contamination.

• Health: Arsenic is a carcinogen. Long-term exposure can lead to skin lesions, respiratory issues, and damage to internal organs.

Safety Precautions:

• Proper personal protective equipment (gloves, mask, goggles) should be used when handling arsenic and its compounds.

• Arsenic waste must be disposed of in a way that does not harm the environment.

Conclusion:

Arsenic metal plays an important role in industries such as semiconductors and wood preservation. However, due to its toxic nature, safety precautions must be taken during use, and environmental impacts must be minimized. The use of arsenic-containing products is now restricted or banned in many countries.