I get bored easily. Very easily. Since the Olympics are beginning soon I decided to put together a list of world champion substances and materials; unfortunately we only award gold here. Times-a-wasting, so here we go!
Most acidic:
The chemical structure of fluoroantimonic acid.
Our first winner is fluoroantimonic acid (HSbF6). This superacid is 20 quintillion times stronger than 100% sulfuric acid. It is formed by the exothermic reaction of hydrogen fluoride (HF) and antimony pentafluoride (SbF5); although effectively ‘naked’ the proton is always attached to a fluorine atom by a very weak dative bond which is why it is so acidic.
Most basic (alkali):
A superbase has a very high affinity for protons and is easily destroyed by water, oxygen and carbon dioxide due to deprotonation. So I will say that the winner here is the hydroxide ion (OH–). However although it is the strongest base possible in aqueous solutions, stronger bases exist, just not in water.
Most corrosive:
Coming in as joint winners Argon or Oxygen plasma are the most corrosive substances in the world. They can be made to oxidize just about anything down to its simplest molecular oxide whether it be glass, metal or a polymer, it makes no difference. The plasma is made in-situ by streams of argon and oxygen that are heated by a radio frequency power supply. The atoms of gas can be heated to insanely high temperatures and values as high as 100,000,000 Kelvin have been reported. Want something corroded? Just throw it in, it will disappear quickly enough.
Densest:
Osmium. Nothing more. Nothing Less.
Osmium wins as the densest naturally occurring substance at standard temperature and pressure at 22.59g/cm3. It wins by 0.03g/cm3 just pipping Iridium to the title.
Hardest:
Diamond? Not any more, as lonsdaleite (also known as hexagonal diamond), a carbon allotrope, wins as the hardest substance. It forms naturally when graphite-containing meteorites strike the earth. The immense heat and stress of the impact transforms the graphite into diamond, but retains graphite’s hexagonal crystal lattice. A pure simulated sample was found to be 58% times harder than diamond.
Strongest (tensile):
Walls of carbon nanotubes.
The winner here is (multiwalled) carbon nanotubes, yet another carbon allotrope, this time with a cylindrical structure. It has the highest tensile strength of any material yet measured, with labs producing them at a tensile strength of 63 GPa (yet this is still well below their theoretical limit of 300 GPa).
Highest Young’s modulus:
Finish(ing first). The Diamond standard.
It was bound to win something; diamond is the substance with the highest (measured) Young’s modulus. The world’s most famous carbon allotrope has a gleaming Young’s modulus of 1220 GPa (pun intended).
Toughest:
(Titanium-based) Metallic glass. Looks just like metal.
Metallic glass, created by scientists in California, is found to be the toughest material on the planet, beating steel. The glass is microalloy made of palladium that has a chemical structure that counteracts the inherent brittleness of glass, but maintains its strength. It’s not very dense and it is more lightweight than steel, with comparable heft to an aluminium or titanium alloy.
Most electronegative:
As every educated chemist should know, fluorine wins as the most electronegative element with an electronegativity of 4.0.
Most electropositive:
Francium in water = Bad, bad idea
Francium wins as the most electropositive element. It is at the bottom of its group on the Periodic table and it loses electrons very easily.
Highest melting point:
Tantalum hafnium carbide (Ta4HfC5) is the substance with the highest melting point at 4488 Kelvin. This beats carbon which only has a melting point of 4427 Kelvin.
Highest boiling point:
Here I am going with joint winners. Either Tantalum carbide (TaC) or Tungsten wins, as they both have boiling points that range between 5770-5950 Kelvin.
Most flammable:
Burns through sand. Nuff said.
Chlorine trifluoride (ClF3) explodes as the most flammable substance on the planet (the puns just keep coming). An extremely powerful oxidizing agent, chlorine trifluoride is extremely reactive with most inorganic and organic materials, even plastics, and will initiate the combustion of many materials without a source of ignition. If that’s not scary enough, in an industrial accident, a spill of 900 kg of chlorine trifluoride burned through 30 cm of concrete and 90 cm of gravel beneath it.
Most radioactive:
Gulp !
Polonium-210, I would say, wins as the most radioactive substance on the planet. It is so radioactive that it glows blue because the air around it becomes excited by the radiation it releases.
Most toxic:
Mr Plastic, in the flesh.
The winner here is the botulinum toxin (C6760H10447N1743O2010S32), produced by the bacteria Clostridium botulinum and used in Botox, is the most toxic substance on the planet. In fact, an amount equal to a grain of salt would be enough to kill a 200 Ib man.
Fastest (natural) acceleration:
Try to blink and you’ll miss it.
It is really chemistry but the Pilobolus fungi can accelerate its spores at roughly 20,000 G; that’s equivalent to 33,381ms-2 at sea level or launching a human through the air at 100 times mach speed. Now that’s fast!
Although I deviated a little from chemistry near the end, I hope you enjoyed reading about these world champion substances and materials. If you disagree with any of them or think I should include another category feel free to comment.
Sources:
http://en.wikipedia.org/wiki/Orders_of_magnitude_(density)
http://en.wikipedia.org/wiki/Lonsdaleite
http://en.wikipedia.org/wiki/Fluoroantimonic_acid
http://en.wikipedia.org/wiki/Superbase
http://chemistryiit.blogspot.co.uk/2008/11/super-acids-and-super-base-concepts.html
http://en.wikipedia.org/wiki/Ultimate_tensile_strength
http://www.popsci.com/technology/article/2011-01/new-metallic-glass-toughest-strongest-material-yet
http://en.wikipedia.org/wiki/Young’s_modulus
http://answers.yahoo.com/question/index?qid=20070712141046AApzEj2
http://en.wikipedia.org/wiki/Chlorine_trifluoride
By Myles Scott – The Demotivator
Science - Joy - Life 
There is so little francium in the world though that you can never really react it with water. On the other hand, cesium with water is quite fun.
Very true, but imagine if we could the resulting reaction would be very aesthetically pleasing to the chemist’s eye.
Either way francium still wins as most electropositive element 🙂