Sodium (Na)
“A metal so eager to shed one electron that a pea-sized piece dances across water, fizzing — sometimes bursting into flame.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
The notes
Characteristics
- Configuration 1s² 2s² 2p⁶ 3s¹ — a single, loosely held valence electron, placing sodium in Period 3, Group 1 with the alkali metals; losing it leaves the Na⁺ ion.
- In water it erupts: 2Na + 2H₂O → 2NaOH + H₂. The reaction’s heat often sets the hydrogen alight while the metal skims and hisses across the surface.
- Inside the body Na⁺ is a working ion: nerve messages fire as sodium-potassium ion traffic, and blood plasma keeps its saltiness thanks to sodium.
- Never found free in nature — sea water holds vast reserves of dissolved NaCl, and underground rock-salt seams are the dried floors of ancient seas.
A soft, silvery-white metal you can cut with a kitchen knife — the fresh face shines for a moment, then air dulls it. It is so light (density 0.97 g/cm³) that pieces float on water, and it is always kept drowned in kerosene to shut out air and moisture.
Where you meet it
✦ Uses
- Table salt (NaCl) — flavouring every meal and preserving fish, and serving as the raw material for the chlorine, caustic soda and soap industries.
- Sodium-vapour street lamps — many highway and factory lights still pour the warm yellow-orange glow made by excited sodium atoms.
- Normal saline (0.9% NaCl) drips and ORS sachets — Bangladeshi clinics and homes rely on both to refill lost sodium and water in dehydration.
- Liquid sodium coolant — fast-breeder nuclear reactors circulate molten sodium because it carries heat superbly without slowing the neutrons.
◍ Everyday examples
- The salt cellar at every meal and the salted hilsa Bangladeshis love — sodium chloride working as preservative and taste-maker.
- A hospital saline drip or a pharmacy ORS sachet during a bout of diarrhoea — sodium salts streaming back into the body.
- The yellow-orange streetlight burning over a night market — excited sodium atoms writing their signature in light.
History & name
For thousands of years humanity knew sodium only as a prisoner inside salt and soda ash. In late 1807 Humphry Davy at the Royal Institution in London pushed an electric current through molten caustic soda (NaOH) — and shining globules of a new metal gathered at the cathode, weeks after he had electrolysed potash to win potassium. It was the first proof that electric current could tear a metal out of its compound, and it opened the door to modern electrochemistry. The name traces to “soda”, while the symbol Na keeps faith with Latin natrium, from the natron salt the ancient Egyptians mined for washing and embalming.