Sodium
Sodium is a soft, silvery-white alkali metal so reactive that it's never found free in nature, always bound up in compounds like common table salt. It reacts vigorously with water and tarnishes almost instantly in air, yet in ionic form it's essential to how nerves and muscles function in every animal, including humans.
- Group · Period
- 1 · 3
- At room temp
- solid
- Melts at
- 370.95 K
- Density
- 0.97 g/cm³
- Discovered
- 1807
Uses
Sodium compounds are everywhere in daily life — sodium chloride is the salt used in cooking and food preservation, and sodium bicarbonate (baking soda) and sodium hydroxide (lye) are staples of both the kitchen and heavy industry, the latter used in huge quantities to manufacture paper, soap, and countless other chemical products. Sodium vapor lamps, valued for their efficiency, have long been used in street and industrial lighting.
Sodium metal itself, rather than its compounds, has more specialized industrial uses, including as a reducing agent in certain metal extraction processes and, mixed with potassium, as a heat-transfer fluid in some nuclear reactor designs, taking advantage of its excellent thermal conductivity in liquid form.
History
Sodium was first isolated in 1807 by English chemist Humphry Davy, who passed an electric current through molten sodium hydroxide, or caustic soda, using the recently invented technique of electrolysis. This let him separate the reactive metal from the compound for the first time. Its name reflects that origin, coming from “soda,” while its chemical symbol, Na, comes from natrium, the Latin name for sodium carbonate-containing minerals.
Fun facts
- Sodium reacts violently with water, producing hydrogen gas and enough heat that the reaction can ignite on its own.
- It's a vital electrolyte in the human body, essential for nerve signaling and fluid balance, which is why sodium levels in food and blood matter so much for health.
- Sodium vapor streetlights glow with a distinctive orange-yellow color, caused by excited sodium atoms emitting light at a very specific wavelength.
Frequently asked questions
Why does sodium react so violently with water?
Sodium has a single, loosely held electron in its outer shell that it readily gives up. When it hits water, that electron transfer happens fast and releases a lot of heat, producing hydrogen gas so quickly that the heat generated can ignite the hydrogen, especially with larger pieces of sodium.
Is sodium metal the same thing as table salt?
Not at all. Sodium metal is a soft, highly reactive silvery substance that has to be stored away from air and water. Table salt, sodium chloride, is a completely different, stable compound formed when sodium reacts with chlorine — the extreme reactivity of the metal is essentially neutralized once it's locked into that ionic bond.
Why do older streetlights glow orange instead of white?
Many older streetlights use sodium vapor, which emits light at a very specific yellow-orange wavelength when electrically excited. It's an efficient way to produce visible light, even though the narrow color range makes it look quite different from the whiter light of newer LED streetlights.
Compounds
14 notable compounds containing Na
- Na2B4O7·10H2Omineral
Borax
A hydrated sodium borate mineral built from linked boron-oxygen rings, crystallizing naturally as soft, colorless crystals in dry lakebeds.
Used for: Laundry booster, metalworking flux, glass and ceramic glazes
- NaHCO3salt
Sodium bicarbonate
A mildly alkaline ionic salt known as baking soda, which releases carbon dioxide gas when it reacts with acids or heat.
Used for: Baking leavening agent, antacid, fire extinguisher and cleaning agent
- NaBrsalt
Sodium bromide
A white crystalline salt closely related to table salt, once widely used as a sedative before safer drugs replaced it.
Used for: Source of bromide ion for photography and as a pool/spa sanitizer
- Na2CO3salt
Sodium carbonate
An alkaline ionic salt known as soda ash or washing soda, historically extracted from the ashes of certain plants.
Used for: Glass manufacturing, water softening, laundry detergent
- NaClsalt
Sodium chloride
Ordinary table salt — an ionic lattice of Na⁺ and Cl⁻ ions in a simple cubic arrangement. It's the most abundant dissolved salt in seawater and the main mineral in rock salt deposits.
Used for: Food seasoning and preservation, de-icing roads, industrial chlor-alkali production
- NaFsalt
Sodium fluoride
A simple ionic salt that dissolves to release fluoride ions, which help strengthen tooth enamel against acid attack.
Used for: Water fluoridation, toothpaste additive, pesticide
- NaOHbase
Sodium hydroxide
A strong ionic base known as lye or caustic soda, highly corrosive and extremely soluble in water.
Used for: Soap and paper manufacturing, drain cleaner, industrial pH control
- NaOClindustrial
Sodium hypochlorite
The sodium salt of hypochlorous acid, sold as a pale yellow-green aqueous solution. It's a strong oxidizer that breaks down pigments and destroys microorganisms.
Used for: Active ingredient in household bleach and water disinfection
- Na2MoO4salt
Sodium molybdate
A white, water-soluble salt used as a convenient soluble source of molybdenum in agriculture and as a corrosion inhibitor.
Used for: Trace-element fertilizer additive and corrosion inhibitor in cooling systems
- NaTcO4salt
Sodium pertechnetate
A water-soluble salt containing technetium-99m that is eluted directly from hospital technetium generators and injected as the workhorse radioactive tracer of nuclear medicine.
Used for: Most widely used radioactive tracer for diagnostic imaging (thyroid and bone scans)
- Na3PO4salt
Sodium phosphate
An alkaline ionic salt of phosphoric acid, sold as trisodium phosphate for its strong grease-cutting cleaning power.
Used for: Heavy-duty cleaning agent, food additive, water treatment
- Na2SeO3salt
Sodium selenite
A white crystalline salt that is the most common source of dietary selenium supplementation, dissolving readily to deliver selenium in a bioavailable form.
Used for: Selenium supplement in animal feed and multivitamins
- Na2SiO3industrial
Sodium silicate
A soluble silicate salt made by fusing sand with sodium carbonate, sold as a thick, syrupy solution commonly called water glass.
Used for: Adhesives, detergent builder, egg preservation
- Na2SO4salt
Sodium sulfate
An ionic salt known historically as Glauber's salt in its hydrated form, colorless and highly soluble in water.
Used for: Detergent filler, glass and paper manufacturing, textile dyeing
Isotopes
21 known isotopes
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| Isotope | Natural abundance | Half-life | Decay mode | Mass excess | Binding energy / nucleon | Decay width |
|---|---|---|---|---|---|---|
| Na-23 stable | 100% | Stable | — | -9,529.85 keV | 8,111.49 keV | — |
Show all 21 isotopes
| Na-17 | — | — | Unknown | 34,719.58 keV | 5,522.77 keV | — |
| Na-18 | — | 0.2 MeV | Proton emission (100%) | 25,037.99 keV | 6,202.22 keV | 2.00 × 105 eV |
| Na-19 | — | 40 keV | Proton emission (100%) | 12,929.38 keV | 6,937.89 keV | 4.00 × 104 eV |
| Na-20 | — | 447.9 ms | Electron capture (100%), ECA (20.05%) | 6,850.49 keV | 7,298.5 keV | 1.02 × 10-15 eV |
| Na-21 | — | 22.49 s | Electron capture / beta-plus decay (100%) | -2,184.86 keV | 7,765.56 keV | 2.03 × 10-17 eV |
| Na-22 | — | 2.6018 Y | Electron capture / beta-plus decay (100%) | -5,181.39 keV | 7,915.66 keV | 5.56 × 10-24 eV |
| Na-24 | — | 14.956 h | Beta-minus decay (100%) | -8,417.9 keV | 8,063.49 keV | 8.47 × 10-21 eV |
| Na-25 | — | 59.1 s | Beta-minus decay (100%) | -9,357.81 keV | 8,101.4 keV | 7.72 × 10-18 eV |
| Na-26 | — | 1.07128 s | Beta-minus decay (100%) | -6,860.78 keV | 8,004.2 keV | 4.26 × 10-16 eV |
| Na-27 | — | 301 ms | Beta-minus decay (100%), Beta-minus, neutron emission (0.13%) | -5,517.79 keV | 7,956.95 keV | 1.52 × 10-15 eV |
| Na-28 | — | 30.5 ms | Beta-minus decay (100%), Beta-minus, neutron emission (0.58%) | -988.32 keV | 7,799.26 keV | 1.50 × 10-14 eV |
| Na-29 | — | 44.1 ms | Beta-minus decay (100%), Beta-minus, neutron emission (21.5%) | 2,679.99 keV | 7,682.15 keV | 1.03 × 10-14 eV |
| Na-30 | — | 48 ms | Beta-minus decay (100%), Beta-minus, neutron emission (30%), B-2N (1.15%) | 8,474.67 keV | 7,501.97 keV | 9.50 × 10-15 eV |
| Na-31 | — | 17.0 ms | Beta-minus decay (100%), Beta-minus, neutron emission (39%), B-2N (0.7%) | 12,246.03 keV | 7,398.68 keV | 2.68 × 10-14 eV |
| Na-32 | — | 13.2 ms | Beta-minus decay (100%), Beta-minus, neutron emission (24%), B-2N (8.3%) | 18,640.15 keV | 7,219.88 keV | 3.46 × 10-14 eV |
| Na-33 | — | 8.0 ms | Beta-minus decay (100%), Beta-minus, neutron emission (47%), B-2N (13%) | 23,780.11 keV | 7,089.93 keV | 5.70 × 10-14 eV |
| Na-34 | — | 5.5 ms | Beta-minus decay (100%), B-2N (50%), Beta-minus, neutron emission (15%) | 31,680.11 keV | 6,886.44 keV | 8.30 × 10-14 eV |
| Na-35 | — | 1.8 ms | Beta-minus decay (100%), Beta-minus, neutron emission (0%), B-5N | 37,831 keV | 6,745 keV | 2.53 × 10-13 eV |
| Na-36 | — | 180 ns | Neutron emission | 45,903 keV | 6,557 keV | 2.53 × 10-9 eV |
| Na-37 | — | 60 ns | Beta-minus decay, Beta-minus, neutron emission | 53,134 keV | 6,403 keV | 7.60 × 10-9 eV |