Cl Chlorine
Element Information, Facts, Properties, Trends, Uses, Comparison with other elements

Chlorine is a chemical element with symbol Cl and atomic number 17. It also has a relative atomic mass of 35.5. Chlorine is in the halogen group (17) and is the second lightest halogen following fluorine.
It belongs to group 17 of the periodic table having trivial name halogens.
Chlorine Facts
Read key information and facts about element Chlorine
Name | Chlorine |
Atomic Number | 17 |
Atomic Symbol | Cl |
Atomic Weight | 35.453 |
Phase | Gas (Diatomic Gas ) |
Color | Yellow |
Appearance | pale yellow-green gas |
Classification | Halogens |
Group in Periodic Table | 17 |
Group Name | fluorine family |
Period in Periodic Table | period 3 |
Block in Periodic Table | p -block |
Electronic Configuration | [Ne] 3s2 3p5 |
Electronic Shell Structure (Electrons per shell) | 2, 8, 7 |
Melting Point | 171.6 K |
Boiling Point | 239.11 K |
CAS Number | CAS7782-50-5 |
How to Locate Chlorine on Periodic Table
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 17 to find Chlorine on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Chlorine on periodic table look for cross section of group 17 and period 3 in the modern periodic table.
Chlorine History
The element Chlorine was discovered by W. Scheele in year 1774 in Sweden. Chlorine was first isolated by W. Scheele in 1774. Chlorine derived its name from the Greek word chloros, meaning 'greenish yellow'.
Obtained it from hydrochloric acid, but thought it was an oxide. Only in 1808 did Humphry Davy recognize it as an element.
Chlorine Presence: Abundance in Nature and Around Us
The table below shows the abundance of Chlorine in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
ppb by weight (1ppb =10^-7 %) | ppb by atoms (1ppb =10^-7 %) | |
---|---|---|
Abundance in Universe | 1000 | 40 |
Abundance in Sun | 8000 | 300 |
Abundance in Meteorites | 380000 | 160000 |
Abundance in Earth's Crust | 170000 | 100000 |
Abundance in Oceans | 19870000 | 3470000 |
Abundance in Humans | 1200000 | 210000 |
Crystal Structure of Chlorine
The solid state structure of Chlorine is Base Centered Orthorhombic.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
Unit Cell Parameters
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
a | b | c |
---|---|---|
622.35 pm | 445.61 pm | 817.85 pm |
and the angles between them Lattice Angles (alpha, beta and gamma).
alpha | beta | gamma |
---|---|---|
π/2 | π/2 | π/2 |
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
Space Group Name | Cmca |
Space Group Number | 64 |
Crystal Structure | Base Centered Orthorhombic |
Number of atoms per unit cell |

The number of atoms per unit cell in a simple cubic, face-centered cubic and body-centred cubic are 1,4,2 respectively.
Chlorine Atomic and Orbital Properties
Chlorine atoms have 17 electrons and the electronic shell structure is [2, 8, 7] with Atomic Term Symbol (Quantum Numbers) 2P3/2.
Atomic Number | 17 |
Number of Electrons (with no charge) | 17 |
Number of Protons | 17 |
Mass Number | 35 |
Number of Neutrons | 18 |
Shell structure (Electrons per energy level) | 2, 8, 7 |
Electron Configuration | [Ne] 3s2 3p5 |
Valence Electrons | 3s2 3p5 |
Valence (Valency) | 5 |
Main Oxidation States | -1, 1, 3, 5, 7 |
Oxidation States | -1, 1, 2, 3, 4, 5, 6, 7 |
Atomic Term Symbol (Quantum Numbers) | 2P3/2 |
Bohr Atomic Model of Chlorine - Electrons per energy level

n | s | p | d | f |
---|
Ground State Electronic Configuration of Chlorine - neutral Chlorine atom
Abbreviated electronic configuration of Chlorine
The ground state abbreviated electronic configuration of Neutral Chlorine atom is [Ne] 3s2 3p5. The portion of Chlorine configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Ne]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 3s2 3p5, electrons in the outermost shell that determine the chemical properties of the element.
Unabbreviated electronic configuration of neutral Chlorine
Complete ground state electronic configuration for the Chlorine atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p5
Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.

Atomic Structure of Chlorine
Chlorine atomic radius is 79 pm, while it's covalent radius is 99 pm.
Atomic Radius Calculated | 79 pm (0.79 Å) |
Atomic Radius Empirical | 100 pm (1 Å) |
Atomic Volume | 22.4129 cm3/mol |
Covalent Radius | 99 pm (0.99 Å) |
Van der Waals Radius | 175 pm |
Neutron Cross Section | 35.3 |
Neutron Mass Absorption | 0.033 |
Atomic Spectrum of Chlorine
Chlorine Chemical Properties: Chlorine Ionization Energies and electron affinity
The electron affinity of Chlorine is 349 kJ/mol.
Valence | 5 |
Electronegativity | 3.16 |
ElectronAffinity | 349 kJ/mol |
Ionization Energy of Chlorine
Refer to table below for Ionization energies of Chlorine
Ionization energy number | Enthalpy - kJ/mol |
---|---|
1st | 1251.2 |
2nd | 2298 |
3rd | 3822 |
4th | 5158.6 |
5th | 6542 |
6th | 9362 |
7th | 11018 |
8th | 33604 |
9th | 38600 |
10th | 43961 |
11th | 51068 |
12th | 57119 |
13th | 63363 |
14th | 72341 |
15th | 78095 |
16th | 352994 |
17th | 380760 |
Chlorine Physical Properties
Refer to below table for Chlorine Physical Properties
Density | 0.003214 g/cm3 |
Molar Volume | 22.4129 cm3/mol |
Elastic Properties
Young Modulus | - |
Shear Modulus | - |
Bulk Modulus | 1.1 GPa |
Poisson Ratio | - |
Hardness of Chlorine - Tests to Measure of Hardness of Element
Mohs Hardness | - |
Vickers Hardness | - |
Brinell Hardness | - |
Chlorine Electrical Properties
Chlorine is Conductor of electricity. Refer to table below for the Electrical properties ofChlorine
Electrical Conductivity | 0.01 S/m |
Resistivity | 100 m Ω |
Superconducting Point | - |
Chlorine Heat and Conduction Properties
Thermal Conductivity | 0.0089 W/(m K) |
Thermal Expansion | - |
Chlorine Magnetic Properties
Magnetic Type | Diamagnetic |
Curie Point | - |
Mass Magnetic Susceptibility | -7.2e-9 m3/kg |
Molar Magnetic Susceptibility | -5.11e-10 m3/mol |
Volume Magnetic Susceptibility | -2.31e-8 |
Optical Properties of Chlorine
Refractive Index | 1.000773 |
Acoustic Properties of Chlorine
Speed of Sound | 206 m/s |
Chlorine Thermal Properties - Enthalpies and thermodynamics
Refer to table below for Thermal properties of Chlorine
Melting Point | 171.6 K (-101.55°C, -150.78999999999996 °F) |
Boiling Point | 239.11 K (-34.04°C, -29.271999999999935 °F) |
Critical Temperature | 416.9 K |
Superconducting Point | - |
Enthalpies of Chlorine
Heat of Fusion | 3.2 kJ/mol |
Heat of Vaporization | 10.2 kJ/mol |
Heat of Combustion | - |
Chlorine Isotopes - Nuclear Properties of Chlorine
Chlorine has 24 isotopes, with between 28 and 51 nucleons. Chlorine has 2 stable naturally occuring isotopes.
Isotopes of Chlorine - Naturally occurring stable Isotopes: 35Cl, 37Cl.
Isotope | Z | N | Isotope Mass | % Abundance | T half | Decay Mode |
---|---|---|---|---|---|---|
28Cl | 17 | 11 | 28 | Synthetic | ||
29Cl | 17 | 12 | 29 | Synthetic | ||
30Cl | 17 | 13 | 30 | Synthetic | ||
31Cl | 17 | 14 | 31 | Synthetic | ||
32Cl | 17 | 15 | 32 | Synthetic | ||
33Cl | 17 | 16 | 33 | Synthetic | ||
34Cl | 17 | 17 | 34 | Synthetic | ||
35Cl | 17 | 18 | 35 | 75.78% | Stable | |
36Cl | 17 | 19 | 36 | Synthetic | ||
37Cl | 17 | 20 | 37 | 24.22% | Stable | N/A |
38Cl | 17 | 21 | 38 | Synthetic | ||
39Cl | 17 | 22 | 39 | Synthetic | ||
40Cl | 17 | 23 | 40 | Synthetic | ||
41Cl | 17 | 24 | 41 | Synthetic | ||
42Cl | 17 | 25 | 42 | Synthetic | ||
43Cl | 17 | 26 | 43 | Synthetic | ||
44Cl | 17 | 27 | 44 | Synthetic | ||
45Cl | 17 | 28 | 45 | Synthetic | ||
46Cl | 17 | 29 | 46 | Synthetic | ||
47Cl | 17 | 30 | 47 | Synthetic | ||
48Cl | 17 | 31 | 48 | Synthetic | ||
49Cl | 17 | 32 | 49 | Synthetic | ||
50Cl | 17 | 33 | 50 | Synthetic | ||
51Cl | 17 | 34 | 51 | Synthetic |
Regulatory and Health - Health and Safety Parameters and Guidelines
Database Search
List of unique identifiers to search the element in various chemical registry databases
Database | Identifier number |
---|---|
CAS Number - Chemical Abstracts Service (CAS) | CAS7782-50-5 |
RTECS Number | RTECSFO2100000 |
CID Number | CID24526 |
Gmelin Number | - |
NSC Number | - |
Compare Chlorine with other elements
Compare Chlorine with all Group 17 elements
Compare Chlorine with all Period 3 elements
Compare Chlorine with all Halogens elements
FAQs
What is the electronic configuration of Chlorine?
The electronic configuration of Chlorine is 1s2 2s2 2p6 3s2 3p5.
What is the abbreviated electronic configuration of Chlorine?
The abbreviated electronic configuration of Chlorine is [Ne] 3s2 3p5. To form abbreviated notation of electronic configuration, the completely filled subshells are replaced by the noble gas of the preceding period in square brackets.
What is the symbol of Chlorine?
Symbol of Chlorine is Cl. Chlorine is a chemical element with symbol Cl and atomic number 17.
What is the position of Chlorine in the Periodic Table?
Chlorine is a chemical element with the symbol Cl and atomic number 17. Chlorine is the 17 element on the periodic table. It is located in group 17 and period 3 in the modern periodic table.
What is the atomic number of Chlorine?
The atomic number of Chlorine is 17.
What is the color of Chlorine?
Chlorine is of Yellow color.
Who discovered Chlorine?
The element Chlorine was discovered by W. Scheele in year 1774 in Sweden. Chlorine was first isolated by W. Scheele in 1774.
How many valence electrons does a Chlorine atom have?
Chlorine has 5 valence electrons. Chlorine has 17 electrons out of which 5 valence electrons are present in the 3s2 3p5 outer orbitals of atom.
What is the melting Point of Chlorine?
Melting Point of Chlorine is 171.6 K.
What is the boiling Point of Chlorine?
Boiling Point of Chlorine is 239.11 K.
What is the melting Point of Chlorine in Kelvin?
Melting Point of Chlorine in Kelvin is 171.6 K.
What is the boiling Point of Chlorine in Kelvin?
Boiling Point of Chlorine in Kelvin is 239.11 K.
What is the electronic configuration of Chlorine 17?
The electronic configuration of Chlorine will be 1s2 2s2 2p6 3s2 3p5.
How do you write the electron configuration for Chlorine?
The electronic configuration of Chlorine will be 1s2 2s2 2p6 3s2 3p5.