Element 17 · Chlorine (Cl)

Chlorine Bohr model: diagram and electrons per shell

The chlorine Bohr model shows a chlorine atom (Cl) as a small nucleus with its electrons circling it in 3 shells: 2 in shell K, 8 in shell L and 7 in shell M. This page has a rotating 3D chlorine Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the chlorine Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of chlorine (Cl), a simplified picture of a single chlorine atom. Its nucleus holds 17 protons, and a neutral chlorine atom has 17 electrons, arranged around it in 3 shells (2 in shell K, 8 in shell L and 7 in shell M).

Cl K · 21s² L · 82s² 2p⁶ M · 73s² 3p⁵

Chlorine Bohr model diagram

Bohr model diagram of chlorine: a nucleus of 17 protons with 17 electrons on 3 shells, 2 in shell K, 8 in shell L and 7 in shell M, each ring labelled with its shell letter. — The chlorine Bohr model drawn flat: each ring is a shell, labelled with its letter, and every dot is an electron (2 in shell K, 8 in shell L and 7 in shell M).

Chlorine electrons per shell

A neutral chlorine atom has 17 electrons, one for each of its 17 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L and 7 in shell M.

Electrons in each shell of the chlorine Bohr model
Shell	Shell number (n)	Electrons	Most it can hold (2n²)	Subshells
K	1	2	2	1s²
L	2	8	8	2s² 2p⁶
M	3	7	18	3s² 3p⁵

How the chlorine Bohr model builds up, shell by shell

Watch the chlorine Bohr model come together: the nucleus first, then each shell in turn, from the innermost outwards, with its electrons joining the ring. The legend names every shell and counts its electrons, so you can read off the arrangement (2 in shell K, 8 in shell L and 7 in shell M) as it forms.

Animation of the chlorine Bohr model being built: a nucleus of 17 protons appears first, then each shell grows in around it and takes its electrons, giving 17 electrons on 3 shells (2 in shell K, 8 in shell L and 7 in shell M). — The chlorine Bohr model built up in six seconds: the nucleus first, then each shell with its electrons, ending with 2 in shell K, 8 in shell L and 7 in shell M. Protons are red, neutrons yellow and electrons blue.

How to draw the chlorine Bohr model

Find the atomic number. Chlorine has atomic number 17, so a neutral atom has 17 protons and 17 electrons.
Draw the nucleus. Put a circle in the centre and write Cl in it. The 17 protons sit there with the neutrons.
Draw the shells. Sketch 3 shells as rings around the nucleus. A shell holds at most 2n² electrons: 2 in the first, 8 in the second, 18 in the third and 32 in the fourth.
Place the electrons. Fill from the inside out: 2 in shell K, 8 in shell L and 7 in shell M.
Check the total. 2 + 8 + 7 = 17, the atomic number, so every electron is accounted for.

Atomic data for the chlorine Bohr model

The numbers behind the chlorine Bohr model, grouped by topic. Radii are in picometres (pm) and energies in kilojoules per mole (kJ/mol).

Identity

Symbol: Cl
Atomic number: 17
Atomic mass: 35.45 u
Family: Halogens
Position: group 17, period 3
Block: p-block

Electron configuration

Full: 1s² 2s² 2p⁶ 3s² 3p⁵
Shorthand: [Ne] 3s² 3p⁵
Electrons per shell: 2, 8, 7
Outer-shell electrons: 7 in shell M

Ionisation energies

I₁: 1251.2
I₂: 2298
I₃: 3822
I₄: 5158.6
I₅: 6542
I₆: 9362
I₇: 11018
I₈: 33604

Energy to remove each electron in turn (kJ/mol). A sharp jump means the next electron comes from an inner shell.

Atomic radii

Calculated (pm): 79
Empirical (pm): 100
Covalent (pm): 99
Van der Waals (pm): 175

Electronegativity and electron affinity

Electronegativity (Pauling): 3.16
Electron affinity (kJ/mol): 348.575

Oxidation states

−1 +1 +3 +5 +7

Charges the element commonly takes in compounds.

Physical properties, abundance and history of chlorine

Bulk properties of chlorine, how common it is, who discovered it and some of its compounds.

Physical properties

Phase at room conditions: Gas
Appearance: Pale yellow-green gas
Melting point: -101.55°C (171.6 K)
Boiling point: -34.04°C (239.11 K)
Density: 0.0032 g/cm³
Thermal conductivity (W/m·K): 0.009
Specific heat (J/g·K): 0.479
Heat of fusion (kJ/mol): 6.41
Heat of vaporisation (kJ/mol): 20.41

Abundance

Earth's crust (mg/kg): 145
Oceans (mg/L): 19400

Discovery

Discovered by: Carl Wilhelm Scheele
Year: 1774

Common compounds

Sodium Hypochlorite ClNaO
Chlorophene C13H11ClO
Crystal Violet C25H30ClN3
Didecyldimethylammonium Chloride C22H48ClN
Benzalkonium Chloride C22H40ClN
Chlorpromazine C17H19ClN2S
Diazepam C16H13ClN2O
Imidacloprid C9H10ClN5O2

Compounds listed in the PubChem database.

Main isotopes of chlorine

Isotopes of chlorine share the same 17 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of chlorine: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
35	75.8 %	stable	–
36	–	301.3 ky	β⁻, β⁺
37	24.2 %	stable	–
38	–	37.23 min	β⁻
39	–	56.2 min	β⁻
40	–	1.35 min	β⁻

α = alpha decay, β⁻ = beta-minus, β⁺ = beta-plus, EC = electron capture, SF = spontaneous fission, p / n = proton / neutron emission.

More about chlorine

Chlorine on the periodic table – properties, isotopes, uses and the full chlorine page.
Halogens – all halogen elements and their trends.
Bohr model of every element – the Bohr model of all 118 elements.