Periodic Table Quiz
A few elements exist only for fractions of a second in a laboratory.
A periodic table quiz with answers that asks about the stories behind the elements rather than their numbers: why symbols look the way they do, who named what and which elements behave oddly.
Did you know?
- Helium was found on the Sun before it was found on Earth. In 1868 astronomers studying sunlight during an eclipse saw a colour that matched no known element. It was named after helios, the Greek word for the Sun, and only detected on our own planet in 1895.
- Aluminium is the most common metal in the Earth's crust, yet in the mid-nineteenth century it was harder to produce than gold. A small pyramid of it was chosen to cap the Washington Monument in 1884. Two years later a cheap process was invented and the price collapsed.
- Technetium, element 43, was the first element to be made artificially. It was identified in 1937 in a piece of metal that had been bombarded in an American accelerator and sent to Italy for study. Its name comes from the Greek word for artificial.
How the periodic table was put together
By the middle of the nineteenth century chemists knew about sixty elements and had noticed that some of them behaved like relatives. In 1869 the Russian chemist Dmitri Mendeleev arranged the known elements by weight and found that their properties repeated at regular intervals. His table worked so well that it was soon accepted, although nobody yet understood why the pattern existed. He even moved a few elements whose measured weights did not fit, trusting the pattern over the data.
Why the pattern works
The explanation came in the twentieth century. In 1913 the English physicist Henry Moseley showed that each element has a fixed number of positive charges in its nucleus, its atomic number, and that this number, not weight, sets the true order. Later work on electrons explained the repeating behaviour: elements in the same column have the same arrangement of outer electrons, which decides how they combine with other atoms.
Metals and the rest
About three quarters of the elements are metals. They fill the left and centre of the table, while non-metals such as carbon, oxygen and the gases of the air sit on the right. The far right column holds gases that almost never react with anything. Only around ninety elements occur naturally on Earth; hydrogen and helium, the two lightest, make up nearly all the ordinary matter in the universe.
Elements made by people
The heaviest elements do not exist in nature. They are created a few atoms at a time by firing one kind of nucleus at another in a particle accelerator, and most of them break apart almost at once. Four such elements received official names in 2016, completing the seventh row and bringing the total to 118. One of them, nihonium, was the first element discovered in Asia.