Rank #1: Helium (He)
(Picture: US National Helium Reserve; Credit: Jonny Dymond/BBC)
Jul 12 2014
Rank #2: Aluminium (Al)
Jul 13 2014
Rank #3: Mercury (Hg)
(Picture: Ghanaian artisanal miner holds mercury in his hand; Credit: Matt Davies/BBC)
Jul 14 2014
Rank #4: Magnesium (Mg)
(Picture: Magnesium alloy flame test; Credit: Magnesium Elektron)
Sep 30 2015
Rank #5: Beryllium (Be)
Image: A man holding a shockproof X-ray tube - Beryllium is used in the construction of these. Credit: Douglas Miller/Topical Press Agency/Getty Images
Oct 22 2015
Rank #6: Potassium (K)
Presenter Justin Rowlatt visits a farm on the Ganges plains to see how this mineral is used, and speaks to the head of the national importer Indian Potash Ltd about their efforts to promote its use by farmers.
We also hear from Paul Burnside, analyst at CRU Group, how a bust-up in Belarus has helped turn potash into a global buyers' market.
Meanwhile Prof Andrea Sella of University College London recreates everyone's favourite school chemistry experiment, with some unexpected consequences...
(Picture: Indian labourer carries bananas in Chennai; Credit: Arun Sankar/AFP/Getty Images)
May 18 2016
Rank #7: Uranium (U)
He is given a tour of the operational power station, Sizewell B, which generates 3% of the UK's electricity, by EDF's head of safety Colin Tucker, before popping next-door to the original power station, Sizewell A, where he speaks to site director Tim Watkins about the drawn-out process of decommissioning and cleaning up the now-defunct reactors.
But while Sizewell remains reassuringly quiet, big explosions come at the end of the programme. We pit environmentalist and pro-nuclear convert Mark Lynas against German Green politician Hans-Josef Fell, the joint architect of Germany's big move towards wind and solar energy, at the expense of nuclear. Is nuclear a green option? It really depends whom you ask.
(Photo: Perdiodic table)
Oct 08 2014
Rank #8: Rare Earth Elements (Ce, Nd, Dy, Er, etc)
(Picture: 20 euro note glows under an ultraviolet light; Credit: Frans Dekkers/Thinkstock)
Jul 21 2014
Rank #9: Carbon (C) - energy
Jul 16 2014
Rank #10: Cobalt (Co)
Jul 22 2015
Rank #11: Lithium (Li)
Jul 22 2014
Rank #12: Hydrogen (H) - fusion
Laurence Knight travels to one such company, Tokamak Energy in the UK, to hear from plasma physicist Melanie Windridge. Meanwhile the BBC's David Willis reports on the string of secretive new fusion initiatives along the Pacific Coast, and the Silicon Valley money backing them.
Plus, could fusion energy open the way to the economic abundance and space travel portrayed in Star Trek? Laurence speaks to Trekonomics author Manu Saadia.
(Picture: Plasma inside a Tokamak fusion reactor; Credit: Tokamak Energy)
May 31 2016
Rank #13: Lead (Pb)
Yet lead in petrol is also accused of having inflicted brain damage on an entire generation of children in the 1970s, as the economist Jessica Wolpaw-Reyes of Amherst College explains. And, producer Laurence Knight travels to one of the UK's only two lead smelters - HJ Enthoven's at Darley Dale in Derbyshire, the historical heartland of the UK lead industry - to see what becomes of the lead in your car battery. And, we speak to the director of the International Lead Association, Andy Bush.
Oct 01 2014
Rank #14: Tungsten (W)
We get a tour of the SGS Carbide tool factory with managing director Alan Pearce, and we consider the market value of this very useful element with Mark Seddon, head of consultancy firm Tungsten Market Research.
Should we worry that China dominates demand? And why is it taking so long to open up new sources? We visit the Hemerdon mining project in the pretty English county of Devon, and hear from Russell Clark, head of the mining firm Wolf Minerals that is reopening it.
And, there is a very special reason why your government should care about its tungsten supplies, as military technology analyst Robert Kelley explains.
(Picture: Soldier lays armour-piercing sabot round on the ground during Operation Desert Shield; Credit: US Department of Defense)
Jul 29 2014
Rank #15: Nitrogen (N) - explosives
(Picture: Early Bosch ammonia reactor in Ludwigshafen; Credit: BASF)
Jul 26 2014
Rank #16: Hydrogen (H) - acids
Aug 19 2015
Rank #17: Titanium (Ti) - catalysts
Presenter Laurence Knight heads to the Ineos oil refinery in Grangemouth, Scotland, to see how just a smidge of a titanium-based catalyst transforms a type of natural gas into the stuff of food packaging, bottles and car bumpers.
He hears from Prof Andrea Sella why most of us spend our lives surrounded by titanium without even realising it.
And Brian Pickett of pigments manufacturer Cristal explains why his company has been painting various bits of London to further the fight against city smog.
(Picture: Window cleaner; Credit: Peter Parks/Getty Images)
Sep 16 2015
Rank #18: Caesium (Cs)
Justin Rowlatt travels to the birthplace of modern time, the National Physical Laboratory in Teddington, England, to speak to Krzysztof Szymaniec, the keeper of the 'Caesium Fountain', and Leon Lobo, the man charged with disseminating time to the UK. He also hears from Felicitas Arias, director of time at the Bureau International des Poids et Mesures in Paris, about plans to abolish the 'leap second'.
And, the Astronomer Royal, Martin Rees, explains why even the atomic clock can never hope to provide an absolute measure of time.
Sep 24 2014
Rank #19: Fluorine (F)
Mar 04 2015
Rank #20: Sulphur (S)
Justin Rowlatt has his hair cut as professor Andrea Sella of University College London, demonstrates sulphur's surprisingly plastic - and acrid - qualities. He travels to the leafy London suburb of Twickenham to find out about Joshua Ward, the charlatan who set up the world's first sulphuric acid factory.
We hear from Richard Hands, editor of Sulphur magazine, about the element's many industrial uses, as well as the gigantic heaps of unwanted sulphur piling up in Canada and Florida. And Mike Lumley, who leads efforts at Shell to make use of the oil giant's sulphur bi-product, explains why the end of acid rain has opened up a surprising new source of demand.
Finally, Justin speaks to Dr Robert Ballard - the man who located the shipwreck of the Titanic - about why he actually considers a sulphur-linked oceanic discovery to be his greatest achievement.
(Picture: Sulphur blocks in Alberta, Canada; Credit: David Dodge/Pembina Institute)
Jul 30 2014