Periodic Table
9
F
18.998
Fluorine
HalogenMost electronegative & most reactive element; anomalous halogen.
Electronic Configuration
1s² 2s² 2p⁵or1s² 2s² 2p⁵
Electron shells
2e⁻n=1
7e⁻n=2
Properties
Atomic number
9
Atomic mass
18.998 u
Category
Halogen
Block / Group / Period
p · 17 · 2
Valence electrons
7
Oxidation states
-1
Electronegativity
3.98
Atomic radius
42 pm
Ionization energy
1681 kJ/mol
Electron affinity
328 kJ/mol
Melting point
53 K / -220 °C
Boiling point
85 K / -188 °C
Density
0.001696 g/cm³
State at 25 °C
gas
JEE / NEET notes
- Most electronegative element (4.0).
- Low bond dissociation energy of F₂ (small size, lone-pair repulsion).
- No positive oxidation state; only −1.
- EA less than Cl (anomaly) due to small size / inter-electronic repulsion.
Exceptions
- • Anomalous halogen — strongest oxidiser, only −1 state, low F–F BDE.
Uses
Toothpaste (fluoride) · Teflon (PTFE) · Uranium enrichment (UF₆) · Refrigerants
Important compounds
HFNaFUF₆SF₆
Personal Notes
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