How do scientists discover new elements/gases/metals etc?


Specifically I was learning about Marie Curie and how she discovered Radium and then Polonium from studying Uranium. It boggles my mind how someone can find a particle and then separate it to find something new let alone someone doing this in the 1800s.

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To be clear: we haven’t discovered any new natural elements since 1939. Any new elements since then were purposefully created.

Some elements like copper lead and gold have been know to humans since ancient times.

More were discovered throughout history, but we only really started to understand what an element was quite recently.

An element is an atom with a certain number of protons.

We have names and now about all the elements starting with a single proton (hydrogen) up to 94 protons (Plutonium). We know there are no new elements to discover there because we know about all the 92 possible elements between those two.

We also know about a number of elements with more than 94 protons. We created those artificially and they are so instable at higher numbers that they only last tiny fractions of a second in some cases.

We have confirmed elements up to 118 or so, but that is mostly theoretical knowledge with little immediate practical relevance.

We are still trying to make atoms with more protons beyond that but that gets harder and they last less time.

There is the idea that at some point we might find an island of stability where newly created elements last a bit longer again, but that having any practical consequences is mostly sci-fi.

Finding new elements in the past first required understanding what elements were.

We have known gold and lead since ancient times, but only understood that they are elements quite recently.

People kept discovering new metals and gasses and stuff all the time, but it took modern understanding of chemistry to figure out which ones were actual elements and not just compounds of other stuff.

Luckily it turns out that there are quite some regular patterns in the way elements behave and once the first few clever people figured out how to arrange them in a grid that would eventually become our modern table of elements, they immediately saw holes in the patter. They could tell that there were missing elements and even guess how they would behave based on the pattern.

By the time the Curies did their experiments most of holes had been filled and the easy stuff had already been found and all that was left was some radioactive elements and things that were rare naturally.

Marie Curie worked with stuff like uranium-ore. Uranium is radioactive and naturally decays into other elements over time, some of that further decays into other elements.

Radium and polonium will eventually appear when you leave Uranium unattended long enough. they behave differently enough for Uranium and other stuff in the samples that it is not too hard to figure out it is something different an describe it and tell where it likely should go in the table of elements.