50 Fun Facts About Sodium

What is sodium's atomic number?

It sits in group 1 of the periodic table, one electron beyond the noble gas neon.

Sodium's chemical symbol Na comes from natrium, a Neo-Latin word derived from what?

Natron is a natural salt of hydrated sodium carbonate that the Egyptians dug from Wadi El Natrun.

The word 'sodium' itself is thought to come from the Arabic 'suda', meaning what?

Medieval Europeans used sodanum, a sodium compound, as a headache remedy.

Who first isolated sodium metal in 1807?

He used electrolysis of sodium hydroxide, and isolated potassium the same year.

Which Swedish chemist first published the abbreviation Na for sodium, in 1814?

A German chemist had proposed the name 'Natronium' for Davy's discovery in 1809.

How is bulk sodium metal usually stored?

Exposed to air it forms sodium oxides; a knife cuts the soft metal easily.

What colour does sodium give to a flame?

Excited electrons dropping from the 3p to the 3s orbital emit light at the D line, about 589 nanometres.

Sodium's D line is named after the letter assigned to it by which scientist in 1814?

He was mapping the dark absorption lines of the solar spectrum, now named Fraunhofer lines.

How many stable isotopes does sodium have?

Twenty isotopes are known; sodium-22 lasts 2.6 years and sodium-24 about 15 hours, the rest under a minute.

Sodium-23 is forged in stars by fusing two atoms of which element?

The carbon-burning process needs temperatures above 600 million kelvin and a star of at least three solar masses.

Sodium is the sixth most abundant element in the Earth's crust. Where does it rank among metals?

Aluminium, iron, calcium and magnesium come ahead of it; potassium sits just behind.

What is the melting point of sodium?

It boils at 883 C; both are lower than lithium's but higher than potassium's, following the trend down group 1.

What two products form when the metal reacts with water?

High-speed footage suggests the resulting explosion is a Coulomb explosion driven by charge repulsion.

Under enormous pressure, around 3 megabars, sodium metal becomes what?

At 1.5 megabars it turns black, at 1.9 transparent red; all these high-pressure forms are insulators.

Metallic sodium is produced industrially by electrolysing molten salt in apparatus named after whom?

Calcium chloride is added to lower the melting point below 700 C; the process was patented in 1924.

Metallic sodium was first made commercially in the 19th century as a step in producing which other metal?

The Hall-Heroult process later made aluminium by electrolysis, ending the demand for large quantities of sodium.

Sodium's alloy with potassium, NaK, is notable for being what at room temperature?

It is used as coolant in reactors that must shut down often, because it will not solidify in the pipes.

Molten sodium is used as the coolant in which type of nuclear power plant?

Its high boiling point lets the reactor run at normal pressure, but it explodes on contact with water.

The first nuclear reactor ever to generate electricity, EBR-I in 1951, was cooled by what?

The 0.2-megawatt experimental breeder reactor achieved criticality in 1950 and demonstrated nuclear breeding.

In high-performance engines, sodium is sealed inside which component to carry heat away?

The partly filled stem works as a heat pipe to cool the valve.

Low-pressure sodium lamps, long used for street lighting, give off what kind of light?

They are extremely efficient but make it impossible to see colours at night.

At what altitude is the sodium layer that astronomers fire lasers at to create artificial 'guide stars'?

The mesospheric sodium layer is fed by meteors; the glowing spot helps adaptive optics correct for turbulence.

Sodium has been detected in the thin exospheres of the Moon and which planet?

The strong D line makes the element easy to spot across the Solar System and in cool stars.

Sodium chloride occurs naturally as which mineral?

Sodium and chlorine are the most common dissolved elements by weight in the oceans.

Roughly what percentage of table salt by mass is sodium?

So one gram of salt carries about 393 milligrams of sodium; a teaspoon holds around 2.3 grams of sodium.

The American Heart Association recommends no more than how much sodium per day?

The average American consumes about 3.4 grams; the US tolerable upper limit is 2.3 grams.

The sodium-potassium pump moves how many sodium ions out of a cell for every ATP molecule it uses?

Two potassium ions come in for every three sodium ions expelled, keeping sodium ten times higher outside the cell.

Which Danish scientist discovered the sodium-potassium pump in 1957 and won a Nobel Prize for it in 1997?

The enzyme is found in the membrane of every animal cell.

The sudden inflow of sodium ions into a nerve cell through voltage-gated channels produces what?

Sodium is the main positive ion in the fluid outside cells and sets its osmotic pressure.

Hyponatremia, common among marathon runners, is a blood sodium level below what?

Drinking too much water during endurance events is a classic cause.

What is the common name for sodium bicarbonate?

It is a leavening agent in baking and, more commonly in Britain and Australia, called bicarbonate of soda.

Sodium hydroxide, or lye, is used to make which everyday product from fats and oils?

That is why it feels slippery on skin: it turns skin oils into soap in a reaction called saponification.

Washing soda got the name 'soda ash' because it was historically extracted from what?

Its decahydrate is washing soda; today it is made from salt and limestone by the Solvay process.

The Solvay sodium carbonate process was perfected in the 1860s by a chemist of which nationality?

Ernest Solvay's ammonia-soda process needs only brine and limestone.

The ancient Egyptians used natron, a natural sodium salt, for what purpose?

It absorbs water and so dried out the body; the mineral came from Wadi El Natrun.

Sodium azide is the gas-forming compound in which safety device?

On ignition it releases nitrogen gas almost instantly.

Which Japanese scientist first extracted monosodium glutamate in 1908 while investigating the taste of kombu?

He named the savoury taste umami; the 'Chinese restaurant syndrome' blamed on MSG has never been demonstrated.

The English word 'salary' comes from the Latin word for what?

The popular claim that Roman legionaries were paid in salt is baseless; nobody knows why the word arose.

Gandhi's 1930 Salt March covered 240 miles from Sabarmati Ashram to which coastal village?

He set out with 78 volunteers on 12 March and broke the salt laws on 6 April.

The Wieliczka Salt Mine, with chapels carved from rock salt, is in which country?

Worked from the 13th century, it produced table salt continuously until 1996.

Roughly how much metallic sodium is produced worldwide each year?

Demand fell after 1970 as tetraethyllead was phased out and titanium found new production routes.

After a nuclear criticality accident, doctors estimate neutron dose by measuring which isotope in the blood?

Neutrons convert some of the blood's stable sodium-23 into the 15-hour isotope.

In 1809 the German physicist Ludwig Wilhelm Gilbert proposed which alternative name for Davy's sodium?

He proposed Kalium for potassium at the same time; only the K and Na symbols survived.

Where does sodium rank in abundance among the elements in the universe?

At 20,000 parts per billion it makes up about 0.002 percent of all atoms.

Roughly how much sodium is dissolved in a litre of seawater?

Sodium and chlorine are the most common dissolved elements by weight in the oceans.

What is the boiling point of sodium metal?

Its melting and boiling points sit below lithium's but above those of potassium, rubidium and caesium.

Squeezed to 1.5 megabars, silvery sodium metal changes to what colour?

At 1.9 Mbar it turns transparent red, and by 3 Mbar it is a clear, colourless solid.

What is the half-life of the cosmogenic isotope sodium-22?

Sodium-24, the other cosmic-ray by-product, lasts just 15 hours; all other isotopes decay in under a minute.

Roughly what percentage of the Earth's crust is sodium?

That makes it the fourth most abundant metal, behind aluminium, iron, calcium and magnesium.

The older Castner process for making the metal electrolysed which compound?

It was pricier than the molten-salt method that replaced it, which adds calcium chloride to lower the melting point.