Most chemical compouds are still unknown to science. How many new ones can we make by combining elements from the periodic table?
The universe is flooded with billions of chemicals, each a tiny pinprick of potential. And we've only identified 1% of them. Scientists believe undiscovered chemical compounds could help remove greenhouse gases, or trigger a medical breakthrough much like penicillin did. But let's just get this out there first: it's not that chemists aren't curious. Since Russian chemist Dmitri Mendeleev invented the periodic table of elements in 1869, which is basically a chemist's box of Lego, scientists have been discovering the chemicals that helped define the modern world. We needed nuclear fusion (firing atoms at each other at the speed of light) to make the last handful of elements. Element 117, tennessine, was synthesised in 2010 in this way. But to understand the full scale of the chemical universe, you need to understand chemical compounds too. Some occur naturally — water, of course, is made of hydrogen and oxygen. Others, such as nylon, were discovered in lab experiments and are manufactured in factories. Elements are made of one type of atom, and atoms are made of even tinier particles including electrons and protons. All chemical compounds are made of two or more atoms. Although it's possible there are undiscovered elements left to find, it's unlikely. So, how many chemical compounds can we make with the 118 different sorts of element Lego blocks we currently know? Big numbers We can start by making all the two-atom compounds. There are lots of these: N2 (nitrogen) and O2 (oxygen) together make up 99% of our air. It would probably take a chemist about a year to make one compound and there are 6,903 two-atom compounds in theory. So that's a village of chemists working a year just to make every possible two-atom compound. There about 1.6 million three-atom compounds like H₂0 (water) and C0₂ (carbon dioxide), which is the population of Birmingham and Edinburgh combined. Once we reach four- and five-atom compounds, we would need everyone on Earth to make three…