Quick Facts
| Property | Value |
|---|---|
| Symbol | As |
| Atomic Number | 33 |
| Atomic Mass | 74.922 u |
| Category | Metalloid |
| Period | 4 |
| Group | 15 |
| Block | p |
| Electron Configuration | [Ar] 3d¹⁰ 4s² 4p³ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 5.727 g/cm³ (gray arsenic) |
| Melting Point | 817°C (1090 K) at 28 atm |
| Boiling Point | 615°C (888 K) sublimes |
| Appearance | Steel-gray, brittle metalloid |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Ar] 3d¹⁰ 4s² 4p³ |
| Electronegativity | 2.18 (Pauling scale) |
| First Ionization Energy | 947 kJ/mol |
| Atomic Radius | 119 pm |
| Covalent Radius | 119 pm |
| Van der Waals Radius | 185 pm |
History and Discovery
Discovered by: Albertus Magnus (attributed) Year of Discovery: ~1250 CE Location: Germany
Etymology
The name "arsenic" comes from Greek "arsenikon," derived from Persian "zarnikh" meaning "yellow orpiment." The Greeks associated it with "arsenikos" (masculine, potent).
Discovery Story
Arsenic compounds have been known since ancient times. Albertus Magnus is credited with isolating the element around 1250 by heating arsenic trisulfide with soap. Arsenic's toxicity made it notorious as a poison throughout history, called "inheritance powder" and "king of poisons."
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ⁷⁵As | 100% | Stable | - |
Occurrence
Natural Abundance
Arsenic comprises about 1.8 ppm of Earth's crust. It is found in over 200 minerals, most commonly arsenopyrite (FeAsS). It often occurs with sulfide ores of other metals. Major producers are China, Morocco, and Russia.
Extraction and Production
- Byproduct: From copper, lead, and gold smelting
- Roasting: Of arsenopyrite ore
- Sources: Arsenopyrite and other arsenic minerals
- Global production: about 35,000 tons annually
Applications and Uses
Semiconductor Industry
- Gallium arsenide (GaAs) semiconductors
- Integrated circuits
- Solar cells
- LEDs
Wood Preservation (Historical/Declining)
- Chromated copper arsenate (CCA)—now restricted
- Historically used for outdoor wood treatment
Agriculture
- Herbicides (historical use, now restricted)
- Pesticides (now largely banned)
Other Uses
- Lead alloys (car batteries, ammunition)
- Glass manufacturing
- Pyrotechnics
Biological Role
Arsenic has no known essential biological role in humans, though some organisms can metabolize it.
In the Human Body
Arsenic accumulates in hair, nails, and skin. The body can metabolize small amounts but chronic exposure is harmful.
Toxicity
Arsenic is highly toxic. It inhibits cellular enzymes and interferes with ATP production. Chronic exposure causes cancer and other serious health effects.
Safety and Hazards
Toxicity
Arsenic is a well-known poison. Arsenic trioxide (As₂O₃) is particularly dangerous. Chronic exposure causes skin lesions, cancer, and organ damage.
Handling Precautions
- All arsenic compounds should be treated as toxic
- Use proper ventilation and PPE
- Arsine gas (AsH₃) is extremely toxic
- Follow strict disposal regulations
- Known human carcinogen (Group 1)
Environmental Impact
Arsenic contamination of groundwater affects millions worldwide, particularly in Bangladesh and India. Mining activities release arsenic into the environment.
Interesting Facts
- Arsenic was called "inheritance powder" because it was undetectable and used to hasten inheritances
- Napoleon may have died from arsenic poisoning (from wallpaper pigment)
- The Marsh test (1836) was developed to detect arsenic in murder investigations
- Arsenic-based drugs were used to treat syphilis before antibiotics
- Some bacteria can "breathe" arsenic instead of oxygen