Tungsten vs Molybdenum

For most of the twentieth century, tungsten lit the world. A coil of tungsten wire heated to more than 2500 °C glows white, and because tungsten melts at a higher temperature than any other metal, it could do this for thousands of hours without failing. The incandescent bulb is fading now, but tungsten has not. Its hardness, heat resistance and sheer density keep it in cutting tools, armour, X-ray machines, welding rods and the tips of darts.

• Tungsten has the highest melting point of any metal, at about 3422 °C, which is why it served as the filament in light bulbs for a century.
• Tungsten is almost exactly as dense as gold, and gold plated tungsten bars have been used in attempts to counterfeit bullion.

Nearly every living thing needs molybdenum, and it is the heaviest element with a role in the human body. Soil and ocean bacteria use a molybdenum enzyme to break the tough bond in nitrogen gas and make ammonia, the process on which most of the world's protein depends. Yet for most of history nobody knew molybdenum existed, because its main mineral looked exactly like lead ore or graphite.

• Molybdenum is the most abundant transition metal dissolved in the oceans, which is why marine microbes evolved to depend on it.
• The enzyme nitrogenase, which lets bacteria turn nitrogen gas into ammonia, has molybdenum at its heart, and most of the protein on Earth passes through it.