Molybdenum

This week's element is molybdenum, which will please the biologists who are reading because it is essential for life. Molybdenum has the symbol Mo and atomic number 42. It is a beautiful, lustrous silver-coloured metal that was often confused with lead, hence its name, which comes from the Greek, molybdos , for lead. Molybdenum is an element of extremes. It is quite brittle but it makes strong alloys that do not expand upon heating when substituted for tungsten. Thus, molybdenum alloys are in demand for aircraft parts, electrical contacts, high-speed drill bits and other items exposed to high temperatures. Molybdenum-based lubricants are also in demand for use at high temperatures. But most important, in my opinion, is that molybdenum is essential for life -- all life, from bacteria to birds. Of course, this includes humans. Interestingly, several studies found that a scarcity of molybdenum in the Earth's early oceans was a limiting factor for the evolution of eukaryotic life (plants and animals) for nearly two billion years. The reason is because eukaryotes cannot capture and use inorganic nitrogen so they depend upon prokaryotic bacteria to capture and "fix" nitrogen into a usable, organic, form (doi: 10.1038/nature06811 ). For this, they have an enzyme known as nitrogenase, that requires molybdenum to function properly. Currently, molybdenum is more common in the oceans than on land; it is the 25th most abundant element in the oceans (average: 10 parts per billion) whereas it is the 54th most abundant element in the Earth's crust -- but it didn't start out this way. Due to the lack of oxygen in the early oceans, molybdenum-containing minerals located on the sea floor did not dissolve and thus, this element was not available to nitrogen -fixing bacteria. Only after oxygen levels increased in sea water was molybdenum available to these microbes, which then fixed nitrogen , making that element available to eukaryotes. This, then supported the ensuing explosive evolutionary diversification of life on earth. Our favourite professor, Martyn Poliokoff, tells us more about molybdenum use by the enzyme nitrogenase: Visit periodicvideos 's YouTube channel [ video link ]. .. .. .. .. .. .. .. .. .. .. .. .. Video journalist Brady Haran is the man with the camera and the University of Nottingham is the place with the chemists. You can follow Brady on twitter @ periodicvideos and the University of Nottingham on twitter @ UniNottingham You've already met these elements: Niobium : Ni , atomic number 41 Zirconium : Zr , atomic number 40 Yttrium : Y , atomic number 39 Strontium : Sr , atomic number 38 Rubidium : Rr , atomic number 37 Krypton : Kr , atomic number 36 Bromine : Br , atomic number 35 Selenium : Se , atomic number 34 Arsenic : As , atomic number 33 Germanium : Ge , atomic number 32 Gallium : Ga , atomic number 31 Zinc : Zn , atomic number 30 Copper : Cu , atomic number 29 Nickel : Ni , atomic number 28 Cobalt : Co , atomic number 27 Iron : Fe , atomic number 26 Manganese : Mn , atomic number 25 Chromium : Cr , atomic number 24 Vanadium : V , atomic number 23 Titanium : Ti , atomic number 22 Scandium : Sc , atomic number 21 Calcium : Ca , atomic number 20 Potassium : K , atomic number 19 Argon : Ar , atomic number 18 Chlorine : Cl , atomic number 17 Sulfur : S , atomic number 16 Phosphorus : P , atomic number 15 Silicon : Si , atomic number 14 Aluminium : Al , atomic number 13 Magnesium : Mg , atomic number 12 Sodium : Na , atomic number 11 Neon : Ne , atomic number 10 Fluorine : F , atomic number 9 Oxygen : O , atomic number 8 Nitrogen : N , atomic number 7 Carbon : C , atomic number 6 Boron : B , atomic number 5 Beryllium : Be , atomic number 4 Lithium : Li , atomic number 3 Helium : He , atomic number 2 Hydrogen : H , atomic number 1 Here's a wonderful interactive Periodic Table of the Elements that is just really really fun to play with! .. .. .. .. .. .. .. .. .. .. .. .. twitter: @ GrrlScientist facebook: grrlscientist email: [email protected]