17 Cl Chlorine 35.45 u

Chlorine

Add one script tag to your page:

<div data-chemfyi="element" data-slug="Cl"></div>
<script src="https://cdn.jsdelivr.net/npm/chemfyi-embed@1/dist/embed.min.js" defer></script>

Embed as an iframe:

<iframe src="https://chemfyi.com/iframe/element/Cl/?style=modern&theme=light" width="420" height="400" frameborder="0" loading="lazy" style="border:0;border-radius:10px;max-width:100%"></iframe>

Paste the URL in WordPress, Medium, or Ghost:

https://chemfyi.com/element/cl/

Shields.io-compatible SVG badge:

Chlorine badge ![Chlorine](https://chemfyi.com/badge/element/Cl.svg)

Web Component:

<chemfyi-element slug="Cl"></chemfyi-element>
<script src="https://cdn.jsdelivr.net/npm/chemfyi-embed@1/dist/embed.min.js" defer></script>
Period
3
Group
17
Block
p-block
Phase (STP)
Gas

Chlorine is a highly reactive halogen used extensively in water purification. It is the second lightest halogen and an essential element for life.

Appearance: Pale yellow-green gas

About Chlorine

A pale yellow-green gas with a sharp odor, chlorine is among the most reactive of the halogens and is used the world over to purify water. It has atomic number 17 and an atomic mass of 35.45, condensing to a liquid at 239 K. Seven valence electrons ([Ne] 3s2 3p5) leave it one short of a stable octet, producing a high electronegativity of 3.16 and a first ionization energy of 1251 kJ/mol. Carl Wilhelm Scheele first produced the gas in 1774. Though hazardous in concentrated form, chlorine is essential to life as the chloride ion. It is the second lightest halogen and sits in group 17, period 3.

Physical Properties

Atomic Mass 35.45 u
Density 0.003214 g/cm³
Melting Point -101.5 °C
Boiling Point -34.0 °C
Phase at STP Gas
Atomic Radius 79.0 pm

Electronic Properties

Electronegativity 3.16
Ionization Energy 1251.2 eV
Electron Affinity 349.0 eV
Valence Electrons 7

Electron Configuration

Configuration [Ne] 3s² 3p⁵

Electron Shell Configuration

Chlorine electron shell configuration Cl 2e⁻ 8e⁻ 7e⁻
Electron shell structure of Chlorine — electrons per shell.
Shell Electrons
1 (K) 2
2 (L) 8
3 (M) 7

Position in Periodic Table

Chlorine position in the periodic table Cl

Discovery

Discovered by: Carl Wilhelm Scheele
Year: 1774

Block & Period

Block

s p d f

Period

1 2 3 4 5 6 7

Periodic Table

Lanthanides Actinides

Reactions Involving Cl

Ammonia and Hydrochloric Acid

NH₃ + HCl → NH₄Cl

Acid-Base

Aqua Regia Dissolving Gold

Au + 3HCl + HNO₃ → HAuCl₄ + NO + 2H₂O

Redox

Barium Sulfate Precipitation

BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl

Precipitation

Chlor-Alkali Electrolysis

2NaCl + 2H₂O → Cl₂ + 2NaOH + H₂

Electrochemical

Hydrochloric Acid and Sodium Hydroxide Neutralization

HCl + NaOH → NaCl + H₂O

Acid-Base
View all 73 reactions →

Compounds Containing Chlorine

1,2-Dichloroethane

C₂H₄Cl₂

Aluminum Chloride

AlCl₃

Ammonium Chloride

NH₄Cl

Atrazine

C₈H₁₄ClN₅

Barium Chloride

BaCl₂

Boron Trichloride

BCl₃

Calcium Chloride

CaCl₂

Calcium Hypochlorite

Ca(OCl)₂

Cerium(III) Chloride

CeCl₃

Chloric Acid

HClO₃

Chloroform

CHCl₃

Chlorosulfonic Acid

ClSO₃H

More Halogen

9 F Fluorine 35 Br Bromine 53 I Iodine 85 At Astatine

Frequently Asked Questions

What is Chlorine?
Chlorine (Cl) is a chemical element with atomic number 17. It is a gas at standard temperature and pressure, classified as a halogen.
What are the key properties of Chlorine?
Chlorine has an atomic mass of 35.45 u, density of 0.003214 g/cm³, melting point of -101.5°C, boiling point of -34.0°C.
What is the electron configuration of Chlorine?
The electron configuration of Chlorine is [Ne] 3s2 3p5. It is in the p-block of the periodic table.
Who discovered Chlorine?
Chlorine was discovered by Carl Wilhelm Scheele in 1774.
What is the electronegativity of Chlorine?
Chlorine has an electronegativity of 3.16 on the Pauling scale.