Eli5: How did humans first find the gasses on the periodic table we use today, and how did they go about collecting it?



Like, did someone just come across helium one day, not knowing what it was, and decided to start collecting it in containers? What about neon, hydrogen, and all the others? How did they know where to look, and even when found, how did they collect it without all the gas escaping into the air around them?

In: Earth Science

They found out things by doing “stuff” and recording the results.

So they would add X to Y and see what happened, then they would put a flame above it, then do something different. All the time while logging everything that happened so they could replicate it.

Not an expert, but the way i see it the easiest way would be to try and isolate it. So for instance, find a substance that, when heated, should give off only one gas (Lets take chlorine for example, which exists in gas form on earth unless bound to something else) and find a liquid that that substance is inert in. Then, submerge it in that liquid and start heating it, and wait for the gas to rise to the top, displacing the liquid in the process. If you now have a vent to fill the gas into, say, a balloon, from the container you isolated it in, you can now start experiments, like weighing it, describing its color, writing some about its properties (Is it corrosive? Is it heavier or lighter than air? etc.)

Helium was first discovered by analyzing the spectrum of sunlight. That’s why it’s named after Helios the sun. It was thought that it only existed on the sun until they were doing checks on the spectrum going through different gases that came up from the earth and they discovered that the same lines appeared as what appeared in the sun.

The gases on the period table where discovered gradually. After we started to make the period table logic predicted that if there is an element with 4 electrons there is probably one with 1, 7, 8 and so on. It was just a matter than of discovering a pure form and naming it. Oxygen was unknown for a long time the only hint people had was that- apparently. A rat under a dome died when closed for to long but a rat under a dome with a plant inside lived longer.

About collecting it. Most non-royal gases (so everything that isn’t helium, neon, argon, xenon) etc. are in other stuff like water is just Hydrogen and Oxygen. You can do something called an „electrolyzing“ process where you use metal and electricty to split up the water and the oxygen goes to one and Hydrogen to the other pole.

That dosn’t only work with water it works with lots of fluid. Royal Gases are a bit tricky. Idk how people did it in the past but nowadays we literally cool down normal breathable air until its liquid. In our air are alot more things than Oxygen. Actually only ~20% of our air is. Its mostly Nitrogen and oh- Royal gases, would you look at that.

Anyway you cool it down till its a liquid, however the different gases have different temperatures where they start to become liquids. So by emptying to tank in between you can, over time, split up the different gases. Imagine if you had a sludge of molten metal with- lets just say. Gold and Iron. Golds melting point is way lower than Irons so the Iron will become solid first, you can than take the iron away and only the gold remains. It works the same with the gases just that you have to manually cool it down.

Helium was discovered by analysing spectral lines from the Sun, and realising that there was an element that that did not exist (or had not been found) on Earth, so they named it after the Sun, (Helios)

Hydrogen was discovered by reacting iron with water. Under anaerobic conditions, this reaction only gives off hydrogen as a gas, so it was pretty easy to produce and contain. They realised that setting fire to hydrogen (reacting it with oxygen) produced water, hence the name *hydro*gen

Argon, krypton, xenon and neon were discovered by liquifying some air, then gradually boiling it. This way, elements and compounds with different boiling points could be separated.

Look up the fascinating early history of research on gases by [Joseph_Black and Antoine_Lavoisier](https://en.wikipedia.org/wiki/Antoine_Lavoisier#Joseph_Black's_%22fixed_air%22). Later on, when it became widely known that air is a mixture of gases, then scientists suspected that there may be others gases, they looked for more, so developed advanced techniques for detecting and collecting them.

Collection was typically into the same type of glass vessels already in use for liquids, just with some closure (above water, for example) to prevent escape.