Bromine puts out fires - both in the home and in the heart. But despite its reputation as an anti-aphrodisiac, this chemical element's biggest use is in fire retardants, found in everything from your sofa to your radio. But do these bromine-based chemicals pose a risk to your health? Presenter Justin Rowlatt hears from chemistry professor Andrea Sella of University College London, about his own childhood encounter with this noxious red liquid. Justin speaks to chemicals industry analyst Laura Syrett of Industrial Minerals about why she thinks bromine may have been the victim of 'chemophobia' - an irrational public prejudice against chemicals. And, the BBC's Mark Lobel travels to the world's biggest source of bromine, the Dead Sea, to see the bromine works of Israel Chemicals Ltd, and comes face-to-face with some of the company's allegedly dangerous products in the hands of deputy head Anat Tal.

Plutonium is one of a family of highly radioactive "synthetic" elements cooked up in nuclear reactors. But does it and its kin have any practical application besides the atom bomb? We travel to plutonium's sunny birthplace to find out.

Already responsible for the IT revolution, could silicon be about to pull off an energy revolution too? We hear from pioneer John Schaeffer about solar power's hippy roots, and Richard Swanson of Sun Power explains why it may be on course to become the world's dominant source of energy. Meanwhile Republican stalwart Barry Goldwater Jr. makes a surprising political bedfellow for solar's traditionally green supporters. (Picture: Californian house covered in solar panels; Credit: Sunrun)

Silicon is synonymous with the computer revolution. We travel to its eponymous birthplace - Silicon Valley in California - to ask chip pioneers Intel why this chemical element has supported a billion-fold increase in computing power, and whether the exponential improvement implied by "Moore's Law" has reached the end of the line.

Sulphur is in abundant supply thanks to its extraction from sour oil and gas, in order to prevent acid rain pollution. But does the world face a glut of this devilish chemical element, famed for its colour and odour? And if so, what uses can it be put to?

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)

Tungsten is one of the hardest, heaviest and highest melting metals, used in everything from bulbs to bullets, x-rays to drill bits. Justin Rowlatt hears from the perennial Professor Andrea Sella of University College London about the properties of what is one of the densest of elements.

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)

Traditionally used as a magic ingredient to produce tougher, more wear-resistant steels, vanadium has discovered a surprising new calling in life. Could this neglected metal, and the gigantic batteries it produces, provide the perfect counterpart for temperamental wind and solar energy sources? And could a future source of the mineral be harvested from the bottom of the sea?

(Picture: Chrome vanadium adjustable spanners and bolts; Credit: runrobirun/Thinkstock)

Nitrogen is a crucial ingredient in fertilisers. And thanks to a pair of clever Germans, the Haber-Bosch process of fixing nitrogen from the air ensures that the planet's burgeoning population can still feed itself. But does it also threaten the planet with an environmental disaster more calamitous than climate change? And could the solution be provided by genetic engineers?

Some 78% of the Earth's atmosphere is nitrogen. Yet this seemingly inert gas is the key component of bombs and explosives. It has brought life and death on an epic scale since mankind first unlocked its potential a century ago. And it has brought tragedy to the lives of the scientists who mastered its potential.

Polymers – or plastics – are enduring, cheap, mouldable and versatile. Yet their very durability mean they litter our landscapes. And their main raw material - crude oil - will not last forever. So could the future be to use nature - with a little tweaking from man - to draw plastics from the atmosphere, and return them at the end of life?