9 F Fluorine 18.998 u

Fluorine

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Period
2
Group
17
Block
p-block
Phase (STP)
Gas

Fluorine is the most electronegative and reactive of all elements. It is used in toothpaste, Teflon, and refrigerants.

Appearance: Pale yellow gas

About Fluorine

No element is more electronegative or more chemically aggressive than fluorine, which tops the electronegativity scale at 3.98 and reacts with almost every other substance. It is a pale yellow halogen of atomic number 9 and atomic mass 18.998, existing as a gas that condenses at 85 K. Seven valence electrons ([He] 2s2 2p5) leave it one short of a filled shell, driving a strong pull on electrons and a first ionization energy of 1681 kJ/mol. Henri Moissan first isolated the reactive element in 1886, a feat that had defeated earlier chemists. Fluorine and its compounds appear in toothpaste, in the polymer Teflon, and in refrigerants. It heads group 17, period 2.

Physical Properties

Atomic Mass 18.998 u
Density 0.001696 g/cm³
Melting Point -219.7 °C
Boiling Point -188.1 °C
Phase at STP Gas
Atomic Radius 64.0 pm

Electronic Properties

Electronegativity 3.98
Ionization Energy 1681.0 eV
Electron Affinity 328.0 eV
Valence Electrons 7

Electron Configuration

Configuration [He] 2s² 2p⁵

Electron Shell Configuration

Fluorine electron shell configuration F 2e⁻ 7e⁻
Electron shell structure of Fluorine — electrons per shell.
Shell Electrons
1 (K) 2
2 (L) 7

Position in Periodic Table

Fluorine position in the periodic table F

Discovery

Discovered by: Henri Moissan
Year: 1886

Block & Period

Block

s p d f

Period

1 2 3 4 5 6 7

Periodic Table

Lanthanides Actinides

Reactions Involving F

Positron Emission of Fluorine-18 (PET Scan)

¹⁸F → ¹⁸O + e⁺ + νₑ

Nuclear

Calcium Fluoride Precipitation (Fluorite)

CaCl₂ + 2NaF → CaF₂↓ + 2NaCl

Precipitation

Fluorine Displacing Chlorine from Sodium Chloride

F₂ + 2NaCl → 2NaF + Cl₂

Single-Replacement

Hydrofluoric Acid and Sodium Hydroxide

HF + NaOH → NaF + H₂O

Acid-Base

Sodium Fluoride and Calcium Chloride

2NaF + CaCl₂ → CaF₂ + 2NaCl

Double-Replacement

Compounds Containing Fluorine

Atorvastatin

C₃₃H₃₅FN₂O₅

Boron Trifluoride

BF₃

Calcium Fluoride

CaF₂

Freon-12

CCl₂F₂

Hydrofluoric Acid

HF

Lithium Fluoride

LiF

Nitrogen Trifluoride

NF₃

Sodium Fluoride

NaF

Sodium Hexafluorophosphate

NaPF₆

Sulfur Hexafluoride

SF₆

Xenon Difluoride

XeF₂

More Halogen

17 Cl Chlorine 35 Br Bromine 53 I Iodine 85 At Astatine

Explore on Science FYI

MineralFYI
Fluorite

Primary fluorine mineral (CaF₂)

Frequently Asked Questions

What is Fluorine?
Fluorine (F) is a chemical element with atomic number 9. It is a gas at standard temperature and pressure, classified as a halogen.
What are the key properties of Fluorine?
Fluorine has an atomic mass of 18.998 u, density of 0.001696 g/cm³, melting point of -219.7°C, boiling point of -188.1°C.
What is the electron configuration of Fluorine?
The electron configuration of Fluorine is [He] 2s2 2p5. It is in the p-block of the periodic table.
Who discovered Fluorine?
Fluorine was discovered by Henri Moissan in 1886.
What is the electronegativity of Fluorine?
Fluorine has an electronegativity of 3.98 on the Pauling scale.