Lithium Is One Of The Lightest Elements - Lighter Than Oxygen

• Sign in
• Register

Michael Anderson, London

• Lithium is not lighter than oxygen. It is, however, about half as dense as water. So it would float on water if it were not too busy reacting with it, like (but not as violently as) the related elements sodium and potassium.

  Tim Green, Bradford, Yorkshire

• The reason is that lithium is much too reactive and has too low a melting point to be much use in hydraulic engineering. A violent reaction takes place on contact between Lithium and water. The heat of reaction is enough to melt the lithium metal and ignite the hydrogen gas that is produced by the reaction. The result is a flaming globule of liquid metal scooting around on the surface. When I was at school this was a favourite demonstration during chemistry classes, but we were less safety conscious in those days.

  Martin Thomas, Farnham, England

• Carbon also has a lower atomic number than Oxygen, but like Lithium exists as a solid, and is much more dense than Oxygen. Floatation occurs because of buoyancy - the difference in density between two objects. This is why Archimedes jumped out of the bath, and is the reason why steel ships can float on water.

  Colin Alway, London UK

• Lithium is the lighest solid and metal and the third lightest element. However it is soft, reacts with oxygen and water and is somewhat toxic. It melts at a relatively low temperature. Not a meterial to build a ship. The next is Beryllium which is physically very good but a deadly poison. Next, Sodium - more reactive than Lithium. Next, Magnesium is somewhat reactive. Next, Aluminium which can be hardened by alloying and used in aircraft etc.

  John Bromilow, Okehampton, England

• Because although a Lithium atom is lighter than an oxygen atom, Lithium has a dense crystalline structure of atoms, whereas oxygen hasn't. This makes Lithium denser than oxygen, and it's density (or, rather, lack thereof) that makes things float. Lithium does float on water -- but stand well back ...

  Anon,

• Because, if I am not mistaken (chemistry class was a long time ago), it is in the group of elements that are highly reactive with water... potassium and caesium are different examples. The further down the periodic table you get, the more reactive they are. Make a boat out of lithium and it would sizzle and fizzle away to nothing. Make a boat out of caesium and it would react far more violenty, presumably resulting in you and your passengers travelling in a far less comfortable manner, and in several pieces.

  Dan Norcott, Loughborough Leicestershire

• Lithium is just too reactive to exist in the pure state. If you remember back to school days, sodium was stored under oil to prevent it reacting with moisture in the air. Lithium is even more reactive. Even its partial oxidation product, lithium hydroxide is used as a fuel in sloid fuel rocket motors.

  Graeme Shaw, Ruislip

• Lithium would dissolve to form Lithium Hydoxide, possibly about as much use therefore as a chocolate teapot. Much more interesting would be Potassium or Sodium which will both ignite.

  Rowan Christou, Lausanne, Switzerland

• Try it if you don't value your eyebrows.

  Mark Lewney, Cardiff, Wales

• Lithium reacts violently with water.

  Paul, Bristol, England

• Have you tried dropping Lithium into water? Useful only for those who wish to be simultaneously cremated and buried at sea.

  Peter Jones, Brussels, Belgium

• Lithium is in fact less dense than water (534 kg/cubic metre, as against 1000 kg/cubic metre). So it does indeed float. However it also undergoes a rather rapid chemical reaction with water, making it somewhat unsuitable for the suggested purpose.

  David Hotham, Hull, UK

• Apart from the physical chemistry/physics thing...it's expensive and has a tendancy to fizz around a lot then burst into flames when you add it to water.

  Steve, london, UK

• Whilst pure lithium is far to soft and reactive for practical use, recently lithium-aluminium alloys, containing a relatively small amount of lithium have become popular in the aerospace industry.

  Prof Harvey Rutt, Southampton, UK

• Well I see no reason why you shouldn't build a boat out of Lithium, if you intend to float on oil, in the absence of air, and make sure that all the rest of the compounds that come into contact with the boat contain Sodium. Other than those little guidelines there is no reason why you shouldn't build a boat out of Lithium.

  Aidan Randle-Conde, Crewe, UK