When I studied physics and chemistry in school I was taught that atoms are composed of protons, nuetrons, and electrons, and that their interactions can explain chemistry and chemical interactions. Now I understand that this is either wildly oversimplified or wildly out of date. Would somebody be able to catch me up, simply, on what the smallest building blocks of out world are and how they interact to create matter?
In: Physics
Close enough actually to still explain what happens in chemistry and with chemical reactions.
Protons and neutrons are not actually elementary particles though, they are composed of three quarks each, two up quarks and a down quark for a proton, and one up quark and two down quarks for a neutron. But unless you get into high energy particle physics, that doesn’t really make a difference from what you knew before.
Level 1: It’s not really wildly oversimplified. Atoms are made up of protons, neutrons, and electrons, and chemistry is determined by how those electrons bond with each other.
Level 2: While electrons are fundamental particles, protons and neutrons are not. They are made up of quarks, which are fundamental particles. Protons are made of two “up” quarks and one “down” quark, while neutrons are made of one up quark and two down quarks.
Level 3: You might’ve learned that electrons inhabit shells with 2, 8, 18 “spaces” for electrons. That’s not exactly true. Electrons are quantum particles, and quantum particles don’t really have a determinate position. So instead of a circular orbit, imagine the electron as having been spread out into a “cloud” of probability density around the nucleus, and the electron collapsing into a single point position when it’s measured. The shape of the cloud is determined by the energy level of the shell. Higher energy orbitals have weirder and weirder shapes.
That’s still true as far as chemical interactions are concerned.
But atoms are made up of quarks and electrons.
The smallest building blocks are
* quarks
* leptons
* guage bosons
* their antiparticles (though some of the guage bosons are their own antiparticle)
You are already familiar with some of these.
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The quarks come in three groups, and each group has 2 quarks:
* Up and Down (the first two discovered)
* Strange and Charm (very similar to the Up and Down, but much heavier.)
* Top and Bottom (once called Truth and Beauty. Also very similar, but heavier still.)
Quarks have an electric charge, and a “color charge”
* Up, Strange and Top have charge +2/3
* Down, Charm and Bottom have charge -1/3.
* The “color charge” of a quark is not fixed.
The simplest way to think of color charge is that a quark can be red, green or blue, and quarks must form combinations with a “neutral” color:
* Eg, you can have three quarks, one of each color (red, green and blue, making a neutral “white” total color charge)
* Or, you can have a quark and an antiquark (eg, red and antired, making a neutral “black” color charge)
* Or, you can have more complicated messes: eg, four quarks and an antiquark, etc.
* There’s a [ridiculous](https://en.wikipedia.org/wiki/List_of_baryons) [zoo](https://en.wikipedia.org/wiki/List_of_mesons) of combinations, in fact, most of which are irrelevant to everyday life.
Of all the combinations of quarks, only two combos are really relevant for chemistry and everyday life:
* up+up+down: this is a proton.
* up+down+down: this is a neutron.
Any other combo will quickly decay into lighter particles.
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Leptons also come in three groups. Within each group, there are two types of leptons.
* There’s the electron, and the electron neutrino.
* There’s the muon (which is very similar to an electron, but heavier) and the muon neutrino.
* There’s the tau particle (which is also very similar to an electron, but much heavier) and the tau neutrino.
Only the electron is really relevant for chemistry:
* The muon and tau particle are not stable, and will decay quickly into lighter particles.
* The neutrinos are extremely light, and almost undetectable. They have no charge. As they travel through space, they gradually transform into one another and back again. There are literally trillions passing through us every second, with no discernible effect.
A free neutron will decay into a proton + an electron + an antineutrino, but the antineutrino flies off quickly with no discernible effect (unless you have a neutrino detector handy, but even then, it will probably just pass straight through it)
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The guage bosons are the “force carrying” particles:
* There’s the photon. That’s responsible for electromagnetic interactions, which is the main kind of interaction for everyday matter at ordinary scales.
* There are the W+, W-, and Z bosons. These are responsible for “weak interactions”, eg a neutron decaying to a proton, or s, c, t or b quarks decaying to lighter ones, or muons and taus decaying.
* There are 8 different types of “gluons”, but they’re all pretty much indistinguishable, and only operate at very short ranges (eg, within a nucleus). They’re responsible for “gluing” quarks together to form protons and neutrons, or “gluing” the nucleus together.
* There’s the Higgs boson, which is responsible for things having mass.
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It is suspected there is also a particle called a “graviton”. Just like a photon is a tiny quantised particle EM radiation, a graviton would be a tiny quantised particle of gravity waves. We haven’t been able to detect gravitons yet.
There are other particles we suspect exist, but haven’t been able to detect yet. Eg, whatever “Dark Matter” is made of.
> that atoms are composed of protons, nuetrons, and electrons, and that their interactions can explain chemistry and chemical interactions.
This is basically true. Processes involving any other particles are usually not regarded as falling under the heading of “chemistry”, though the divisions between academic fields are generally a bit fuzzy and arbitrary.
> simply, on what the smallest building blocks of out world are and how they interact to create matter?
There will probably never be a complete answer to this question, because it’s hard to imagine how anyone could ever be confident that they have found all the smallest building blocks.
The smallest known building blocks of ordinary matter are electrons and quarks. Quarks come in several different varieties: they have a “generation” (up, down, charm, strange, top, or bottom) and a “colour” (red, green, or blue). A proton is made up of two up quarks and a down quark (one red, one green, and one blue). A neutron is made up of two down quarks and an up quark (one red, one green, and one blue). Each quark has a corresponding antiquark, so there are also antiprotons and antineutrons. Other combinations of quarks (including single quarks by themselves) are unstable: some of them pop in and out of existence as part of the interactions between particles, while others only show up under high-energy conditions (e.g. particle accelerators and stars).
There are also some heavier electron-like particles, called muons and tau particles, which are also unstable, and all three of these have corresponding antiparticles. Each of these has a corresponding neutrino. Neutrinos have a tiny mass and interact very weakly with other particles, so they are hard to detect.
Then you have photons, which “mediate” the electromagnetic force, eight types of gluons, which play the same role for the strong nuclear force, the Z particle and two types of W particle, which play the same role for the weak nuclear force, and the Higgs particle, which effectively gives mass to some of the other particles. Those three forces – electromagnetism and the strong and weak forces – are how the different particles interact with each other.
It’s considered very likely that there are still some undiscovered particles: the most likely candidates include a “graviton” to mediate gravity, and a “weakly interacting massive particle” that may make up dark matter.
There is of course the other side of the coin, as light is both a particle and a wave, so are all subatomic particles, they are both waves and particle, depends on the measuring at which point which
For chemistry:
Protons are positively charged and electrons are negatively charged. For chemical reactions, the neutrons don’t matter because they have no charge. Neutrons act like glue to help hold the nucleus together, but they don’t affect reactions with other atoms. Isotopes – elements with the same number of protons but different numbers of neutrons – are *chemically* identical.
Atoms “want” to be electrically neutral. If there are more protons than electrons, the atom will be positively charged and will attract negatively charged electrons until it captures an electron and becomes neutral. If there are more electrons than protons, it will have an overall negative charge and the outermost electrons will be repelled until one manages to escape, so the atom is neutral.
Atoms also want to have completely full (or completely empty) outer electron shells, due to quantum mechanics things. Of course, an atom can’t merely add or subtract electrons because then it would become electrically unbalanced. So, atoms share electrons. Take water: oxygen has six electrons in the outer shell, but eight would make it full. Hydrogen has one in its outer shell, and two would make it full. So, one oxygen atom shares two of its electrons with two hydrogen atoms, which each share their one. All of the atoms get a full outer shell *and* the number of protons and neutrons in the entire molecule add up to be electrically neutral.
If an atom is very close to being very full or very empty, it may be more stable if it does become electrically neutral. These atoms don’t share electrons, they just either take them or give them away and become *ionized*, meaning they have an electric charge. Ions with opposite charges will attract each other and stick together. This is how table salt works: sodium has one extra electron in its outer shell, and chlorine is missing one. The sodium atom gives up its electron and becomes positively charged, and the chlorine atom takes the electron and becomes negatively charged. The positive sodium and negative chlorine stick together as sodium chloride, which is table salt.
Metals tend to have loosely bound outer electrons and they share all of them in a sort of “sea” of loose electrons that bounce around between nuclei. That’s why metals are usually very good conductors.
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