Genius

Years ago, I read a book called, "Surely your Joking, Mr. Feynman", a collection of stories about the prominent physicist Richard P. Feynman, and I very much appreciated his approach to physical and other scientific problems, so I've paid a little attention to works about him and other physicists.
I've been reworking and reorganizing the basics of Physics and Chemistry lately, and I was intending to do more study yesterday, when I ran across a biography of him, entitled, appropriately enough, "Genius". I very much like his freewheeling, unbounded curiosity about physical topics.
While there is something to be said for organization of knowledge, (and I am rigorous about how I organize subjects in my notebooks), in my case too much of it tends to become overly boring and routine. I need room to backtrack and improvise.

I've already laid out the basics of how I'm organizing physics and chemistry, so I'm going to start from there and describe things I am or have been working on. I've been taking another cycle through particle mechanics, and I'm about to start revising my thoughts on particle mechanics systems. I've finally managed to pick up a chemistry book and review the parts that interested me in college chemistry, trying to tie principles of thermodynamics and chemical equilibrium back together. I've also done a sketch of solar system astronomy, which is leading back to geology. In my most recent forays through cataloging chemical substances, water appears near the top of the list, and it's important enough to geology and biology that I'd like to have the numbers at hand for what is called the heat of fusion (associated with freezing and melting), and of vaporization (associated with boiling and condensation, for those unfamiliar with the terms.

Nitrogen

Continuing with the chemistry series:

Nitrogen is fourth on the list of the most abundant chemically active elements in the solar system. Helium and Neon are more abundant, but for all practical purposes, neither of these form compounds. Neon is light enough that most of it has escaped the earth's atmoshere, but significant amounts are found in the sun and the atmospheres of gas giants.
One of the more common forms of nitrogen is the diatomic N2 gas, which is unusually stable, and which combines with other elements only with some difficulty. It's also present, though only to the amount of a few percent, in the atmospheres of Venus and Mars, and it's the predominant gas in the atmosphere of Titan, one of Saturn's moons. I'll discuss the compounds later.

Carbon

I'm continuing with the chemistry series for now.

Carbon is unique among the elements because of its linking ability. No other element has the same ability to form long chains, multiple branches, and linkable rings. Because of this linking ability, it can be found in both compounds and in solid form.
It is fourth on the list of the most abundant elements in the solar system, largely because of the large quantities of methane in the atmospheres of Jupiter, Saturn, Uranus, and Neptune, as well as its presence in the Sun. It's thought to be found in a form like soot in comets and some asteroids.
It's not one of the most abundant elements on earth, very possibly because the lighter carbon-containing compounds were driven away before the earth had formed or while it was forming, but it is quite abundant. Most of earth's supply is found in compounds contained in rock, with a small fraction concentrated as coal. A small fraction of the earth's carbon is found (in combined form) in the atmosphere. However, this small amount is vital to the existence of life, because it is trapped and incorporated into plant life, and then animal life, and re-released into the atmosphere in processes of respiration.

Oxygen

Oxygen is so chemically active that it is seldom found in the atomic form, except where temperatures are so high or ultraviolet radiation so intense that any kind of molecule is regularly disrupted. At earth-normal temperatures, it is normally found in chemical combination with some other elements, but if it is found free, it is usually in molecular form, O2, as a gas.
One of my interests is in science-fictional world building, as a way to apply a few accumulated bits of knowleds, and to give some variety to the way things are.
For astronomical applications, hydrogen is by far the most abundant of the chemical elements, followed by helium. But helium is chemically inert and forms no compounds, at least not at ordinary temperatures. Third on the list in abundance is oxygen.
On the earth, Oxygen is the single most abundant element. Most of it is found in chemical combination with other elements. It is one of the few places where it can be found free in the atmosphere. It poisonous to some forms of bacteria, because of its presence in the atmosphere, environments without free oxygen are rather uncommon on the earth, so the anaerobic bacteria are likewise uncommon. It is continually produced by plants, which are thought to be the ultimate source of it in the atmosphere, and is essential to the respiration of most animals. It is thought that in the earliest stages of the earth's history, there was no oxygen in the atmosphere, which would dramatically alter the conditions of life in ways that are difficult to predict.
There are some applications to industrial processes, as oxygen can be separated from the mixtures and compounds that naturally contain it, although purifying it and liquefying it is inconvenient and expensive enough that it's not done unless there is a significant benefit to be gained.

Hydrogen

I've about decided that presenting my outline of knowledge isn't the best way to generate interest in the subject of independent learning, so I'm going to try something else. In my college course in Chemistry back in the 1970s, I was particularly interested in what it said about the relative abundance of the elements in the universe.
I don't have the tools to reconstruct the natural abundance of elements from principles of nuclear physics, as some physicists have done, but I have managed to find a few tables of abundances of the elements in the solar system. I'm not sure which is considered the "best" or most current information; I'm still looking for it.
For a couple of days I've been working on making a list of molecules or compounds that can be made from these elements. There are quite a few that can be made in the low-density, high-energy environments of interstellar space, but I'm more interested in those that survive in an earth-type environment. I'm also interested in those that are chemically active.
Hydrogen has the lightest and simplest atoms, and is the most abundant of the elements. I'm not sure whether most of it is collected in stars or in free space, but there are three important forms of it. At highest temperatures, it is disassociated into its components, protons and electrons, and is found in the form of plasma. At cooler temperatures, and in most of interstellar space, it is found in the form of hydrogen atoms. At earth-type temperatures, it is found in molecular form, H2. At very low (cryogenic) temperatures, it can be liquefied, and solidified. However, such very low temperatures appear to be uncommon in the universe. There may be a metallic form found at extremely high pressures such as in the interior of Jupiter.
Hydrogen is substantially lighter than the other elements of earth's atmosphere and not only tends to float above the other gases, but its molecules can achieve escape velocity in the upper atmosphere. It only exists on earth because it can be chemically bound to other atoms, but that's another story. In order for it to be used as fuel, it has to be first pried out of these other molecules, which presents a considerable practical disadvantage for advocates of a hydrogen economy.