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The element Sodium is a silvery metallic metal element. Ductile, malleable, forming a variety of interesting crystalline salts Oh! Never mind all that! Get to the point! Sodium... when you put it in water, it EXPLODES! Yes! Bang, it goes! And it makes a mess! See, it starts out being this big ingot of soft slightly pink metal, and you can get a knife and with a bit of effort, slice bits off it. Drop them in water and BANG! They explode! Everyone's seen this in chemistry demonstrations, where a tiny little piece of sodium metal is dropped into a big bowl of water, and it just fizzles all around on the surface and scoots about and it splitters out. But if you get a piece bigger than about three grammes, put it in water, it explodes. In dregs in coffee cups, even smaller pieces will explode*.

Well of course I can't condone this, and I wouldn't recommend you try this at home. In fact, if you've got an ingot of sodium at home, it's best to leave it stored safely away in an inert atmosphere or under oil. Definitely don't be tempted to get the lid off and put it anywhere near any water. Or, you know what might happen... it might just go bang.

If you have a dustbin that you've filled up with water, the introduction of a baked beans can with some sodium inside is not to be condoned, partly because it's dangerous, but also because it can easily depth-charge the dustbin, after which the bin will never hold water again.

Especially not recommended is putting sodium inside a can and dropping it off a cliff into the sea. This can cause pieces of stuff to be thrown up into the air and there to be the sound of falling debris. Running away is also something associated with this kind of thing.

Sometimes, shortly after an experiment involving a five gallon oil drum with some water in, the sodium may cause the oil drum to leave the premises in a vertical direction, after which the phone may ring. "Hello, it's the neighbours. Your cylinder has just landed on our roof".

Regarding the mess caused by explosions involving sodium in water, the sodium turns to sodium hydroxide which is caustic soda. This is extremely alkaline and dissolves all kinds of things. Most notably, it turns your skin into soap. To avoid being turned into soap, it's best to avoid the sodium hydroxide.

Sometimes you'll see chemistry charts which show in an educational theoretical style how if you combine sodium (metal, reactive, tends to explode), with chlorine (poisonous gas, slightly green), it reacts to produce sodium chloride, which is table salt. This is the stuff of textbooks, because if you ever tried it (don't), it would be a bit difficult to get the salt off the walls to put on your fish and chips, assuming there were any walls still there. The reaction of sodium and chlorine is very exothermic, which is a technical way of saying "it explodes".

I am one of the few people to have seen liquid sodium (and lived to tell the story). My reputation as a mad scientist was considerably propagated the day I heated some sodium metal on a shovel with a blowlamp. I was in the cellar of the building and I was showing a few brave onlookers who dared to get their feet wet (the cellar was almost always flooded). Amazingly the sodium melted to produce globules of molten sodium which rolled about on the shovel like lead or like mercury. Surprisingly it didn't catch fire, which is curious because sodium in air has a tendency to combine with oxygen. Everyone ran away because the next thing that happened was I shoved the liquid metal sodium off the shovel across the water on the floor where it exploded in a myriad of tiny fireworks of bright yellow fire. Spectacular! The trouble is that sodium in water produces clouds of acrid smoke which is corrosive and smells very distinctive. By now this was coming up through the carpets of the shop on the ground floor and the business had to be shut down for the rest of the day.

Some of the stars in the sky have sodium in them. This is known to be true because it's possible to project the light from the stars as a rainbow spectrum and see there are two missing yellow lines. These are the sodium d lines, the same yellow colour that comes off those notorious sodium streetlamps.

Sodium streetlamps don't work by burning sodium, but by an effect more like neon lights, where the atoms have electrons rising and falling through energy states which give off distinctive colours of light. With sodium, it's yellow.

Whereas with gold, the metal is yellow in its solid state, sodium metal is slightly pink. It's shiny, but tarnishes within a few seconds to leave an oxide which is white. The sodium metal is soft, and can be cut with an axe or a knife, with a bit of effort. It's harder than cheese or Blu-Tack, but much softer than lead or aluminium. It gets warm if left in air because the dampness in the air is reacting with the sodium. It does this in a less subtle way than boron which behaves oddly with air and vapour.

Although sodium is metallic, you don't see things made of it. The environment and it don't go together well. On different planets, different environments are more or less inert or active, and at different temperatures. The Earth's atmosphere is such that even though sodium is a metal, it's not practical to make bicycles of it. Not only would there be a problem with rain, but with the air itself. On colder worlds with less reactive atmospheres, sodium would appear quite different.

The word SODIUM is almost a swear word to astronomers as the notorious yellow/orange street lights have a tendency to illuminate the muck in the sky and so obscure the interesting celestial stuff beyond. The problem is known as light pollution and has recently (zero-zeros decade) acquired the special status of "statutory nuisance".

Most sodium is of atomic weight 23 and is stable 2311Na. Heavier isotopes (24 or more) usually give off beta particles (electrons), whereas lighter isotopes (22 or less) usually give off positrons (antimatter).

* The "explosions improved in dregs of coffee (in comparison to water)" theory was originally found to be valid, but later experiments have shown results counter to this. It may be that other effects were involved, for example the shape of the cup, the nature of the stuff in the dregs of coffee, possibly things to do with milk or sugar, etc. Obviously some more experiments need to be done.