Element 9 · Fluorine (F)

Fluorine Bohr model: diagram and electrons per shell

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

Rotate the fluorine Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of fluorine (F), a simplified picture of a single fluorine atom. Its nucleus holds 9 protons, and a neutral fluorine atom has 9 electrons, arranged around it in 2 shells (2 in shell K and 7 in shell L).

F K · 21s² L · 72s² 2p⁵

Fluorine Bohr model diagram

Bohr model diagram of fluorine: a nucleus of 9 protons with 9 electrons on 2 shells, 2 in shell K and 7 in shell L, each ring labelled with its shell letter. — The fluorine Bohr model drawn flat: each ring is a shell, labelled with its letter, and every dot is an electron (2 in shell K and 7 in shell L).

Fluorine electrons per shell

A neutral fluorine atom has 9 electrons, one for each of its 9 protons. They fill the shells from the nucleus outwards: 2 in shell K and 7 in shell L.

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

How the fluorine Bohr model builds up, shell by shell

Watch the fluorine 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 and 7 in shell L) as it forms.

Animation of the fluorine Bohr model being built: a nucleus of 9 protons appears first, then each shell grows in around it and takes its electrons, giving 9 electrons on 2 shells (2 in shell K and 7 in shell L). — The fluorine Bohr model built up in six seconds: the nucleus first, then each shell with its electrons, ending with 2 in shell K and 7 in shell L. Protons are red, neutrons yellow and electrons blue.

How to draw the fluorine Bohr model

Find the atomic number. Fluorine has atomic number 9, so a neutral atom has 9 protons and 9 electrons.
Draw the nucleus. Put a circle in the centre and write F in it. The 9 protons sit there with the neutrons.
Draw the shells. Sketch 2 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 and 7 in shell L.
Check the total. 2 + 7 = 9, the atomic number, so every electron is accounted for.

Atomic data for the fluorine Bohr model

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

Identity

Symbol: F
Atomic number: 9
Atomic mass: 18.9984 u
Family: Halogens
Position: group 17, period 2
Block: p-block

Electron configuration

Full: 1s² 2s² 2p⁵
Shorthand: [He] 2s² 2p⁵
Electrons per shell: 2, 7
Outer-shell electrons: 7 in shell L

Ionisation energies

I₁: 1681
I₂: 3374.2
I₃: 6050.4
I₄: 8407.7
I₅: 11022.7
I₆: 15164.1
I₇: 17868
I₈: 92038.1

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): 42
Empirical (pm): 50
Covalent (pm): 64
Van der Waals (pm): 147

Electronegativity and electron affinity

Electronegativity (Pauling): 3.98
Electron affinity (kJ/mol): 328.165

Oxidation states

−1

Charges the element commonly takes in compounds.

Physical properties, abundance and history of fluorine

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

Physical properties

Phase at room conditions: Gas
Melting point: -219.67°C (53.48 K)
Boiling point: -188.12°C (85.03 K)
Density: 0.001696 g/cm³
Thermal conductivity (W/m·K): 0.028
Specific heat (J/g·K): 0.824
Heat of fusion (kJ/mol): 0.51
Heat of vaporisation (kJ/mol): 6.54

Abundance

Earth's crust (mg/kg): 585
Oceans (mg/L): 1.3

Discovery

Discovered by: André-Marie Ampère
Year: 1886
Named by: Humphry Davy

Common compounds

Dexamethasone C22H29FO5
Flumequine C14H12FNO3
Droperidol C22H22FN3O2
Dichlofluanid C9H11Cl2FN2O2S2
Astemizole C28H31FN4O
Ciprofloxacin C17H18FN3O3
Flucytosine C4H4FN3O
5-Fluorouracil C4H3FN2O2

Compounds listed in the PubChem database.

Main isotopes of fluorine

Isotopes of fluorine share the same 9 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of fluorine: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
17	–	64.37 s	β⁺
18	–	109.734 min	β⁺
19	100 %	stable	–
20	–	11.006 s	β⁻
21	–	4.158 s	β⁻
22	–	4.23 s	β⁻, β⁻n

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

More about fluorine

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