Chlorine (symbol Cl, atomic number 17) is a greenish toxic gas used to disinfect water and the other half of table salt. It is classified as a halogen and sits in group 17, period 3 of the periodic table.
Overview
Chlorine is the chemical element with atomic number 17 and the symbol Cl. With a standard atomic weight of 35.45, it is a halogen. In the periodic table it occupies group 17 and period 3, and under standard conditions it is normally a gas. Chlorine is a greenish toxic gas used to disinfect water and the other half of table salt.
Atomic structure
An atom of Chlorine has 17 protons in its nucleus and, when neutral, 17 electrons arranged in the configuration [Ne] 3s2 3p5. Its standard atomic weight of 35.45 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Chlorine was discovered in 1774 by Carl Wilhelm Scheele. It follows Sulfur (S) and precedes Argon (Ar) in order of atomic number.
| Atomic number | 17 |
|---|---|
| Symbol | Cl |
| Atomic mass | 35.45 |
| Category | Halogen |
| Group | 17 |
| Period | 3 |
| Electron configuration | [Ne] 3s2 3p5 |
| Phase at STP | Gas |
| Discovered | 1774 (Carl Wilhelm Scheele) |