Atomic Properties of Cl
- Atomic Number of Cl
- 17
- Atomic Mass of Cl
- 35.4500 u
- Electron Configuration
- [Ne] 3s2 3p5
- Electronegativity
- 3.16
- Block
- p-block
- Group
- 17
- Period
- 3
Chlorine (Cl) is element 17 on the periodic table. Atomic mass of Cl: 35.4500 u. Cl is in period 3, group 17. Melting point of Cl: 171.60 K.Density of Cl: 0.00 g/cm³.
The element that purifies your water and seasons your food
Chloride ions essential for stomach acid (HCl), nerve function, and fluid balance. Your body contains about 95g of chlorine as chloride.
Discovered by Carl Wilhelm Scheele in Sweden, 1774
Name origin: Greek: chlôros (greenish yellow).
Halogen element. Poisonous greenish-yellow gas. Occurs widely in nature as sodium chloride in seawater. Reacts directly with many elements and compounds, strong oxidizing agent. Discovered by Karl Scheele in 1774. Humphrey David confirmed it as an element in 1810.
Chlorine has 2 naturally occurring isotopes, plus 1 notable radioactive isotope.
| Isotope | Atomic Mass (u) | Abundance | Half-Life | Decay Mode |
|---|---|---|---|---|
| 3517Cl (Cl-35)Chlorine-35 isotope | 34.96885268 | 75.76% | — | — |
| 3617Cl (Cl-36)Chlorine-36 isotope | 35.96830681 | 0% | 301,000 years | β⁻, β⁺, EC |
| 3717Cl (Cl-37)Chlorine-37 isotope | 36.9659026 | 24.24% | — | — |
Data source: NIH PubChem (aggregated from IUPAC, NIST)
Isotopes of Chlorine have important real-world applications in science and industry.
Radioactive 36Cl provides a useful tool to determine ages in geology and hydrology. Some radioactive 36Cl is cosmogenic and enters the terrestrial environment in precipitation. Because of its long half-life of 3.01×105 years, the level of 36Cl in aquifers can be measured and used to estimate ages (on the order of 105 to 106 years) of old meteoric groundwater (water that was originally precipitation) [155]. Thermonuclear bomb tests in the ocean produced large amounts of 36Cl by neutron reactions with 35Cl in seawater. This was especially prevalent in the late 1950s. Large amounts of this anthropogenic 36Cl were distributed throughout the atmosphere, deposited with precipitation, and incorporated into terrestrial soils and groundwater. This enriched 36Cl has been used as a tracer of meteoric water from that era [156].
Used in water purification, bleaches, acids and many, many other compounds such as chlorofluorocarbons (CFC).
Salt (sodium chloride, NaCl) is its most common compound. Commercial quantities are produced by electrolysis of aqueous sodium chloride (seawater or brine from salt mines).
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