We’re up to element 7 in our International Year of the Periodic Table series: Nitrogen. This element was feeding the world long before Band Aid made it cool, and also makes up the bulk of the air that surrounds us.

78% of air is nitrogen, making it the most common element in the Earth’s atmosphere. It’s colourless, odourless, tasteless, and unreactive. Its presence in the atmosphere does have some visible effects, however. It’s responsible for the blues and purples seen in aurora, caused by interaction with charged particles from the sun. The blue tinge of lightning also owes its colour to emissions from nitrogen atoms.

Though nitrogen is largely inert in the atmosphere, it can be ‘fixed’ by microorganisms in the soil. This process produces nitrogen compounds which are a vital source of nitrogen for plants. Plants rely on nitrogen for growth, and we rely on nitrogen for food – but we can’t produce enough food with fixed nitrogen in the soil alone. This is why nitrogen-based fertilisers are needed; it’s estimated that half of the global population is reliant on food produced by these fertilisers.

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.