Today, two elements in the last group of the Periodic Table, Group 18: radon and argon.
Radon is found towards the bottom of the group; it is a heavy element that is unstable and therefore radioactive. It has a half-life of only 3.5 days so doesn’t hang around for long, but is continually generated from the radioactive decay of uranium and thorium in the earth’s crust. As it is gaseous, it can seep through rocks and soil and into houses, often accumulating in basements and other spaces at the bottom of a house. The level of radon, and whether there is enough to pose a health risk should it find its way into your home, depends on the local geology. For instance, the flatlands of East Anglia are relatively safe but the granite of the West Country carries a higher risk, as shown by the map published by Public Health England: https://www.ukradon.org/information/ukmaps
But while radon is a risk to some householders, there are other noble gases that can help make a house a home. Argon, depicted by window frames, is used to fill the space between panes of double-glazed windows as it is a better insulator than air. Krypton and xenon lower down the group can also be used and are actually more effective, but as argon constitutes about 1% of air and krypton and xenon less than 0.1% each, argon is much cheaper and the best balance between performance and cost.
Aside from in windows, argon found another use in our homes as the unreactive gas in traditional incandescent light bulbs. It is not the only noble gas to find use in lighting, but more of that in the next post.