How Do Scientists Know So Much About Atoms?

IANAScientist. Yet just from my high school chemistry class, even I know alot about atoms. Protons and neutrons are in the center (i.e., nucleus), and are bound by an incredibly strong force. Electrons are much smaller than protons or neutrons. And they zip around the nucleus in orbit at an incredible speed. Furthermore, relative to their size, electrons are an incredible distance away from the nucleus. Indeed, matter is mostly empty, you could say. Also, they didn’t mention this in hs. But protons are made up of a smaller particle called “quarks”–or something:confused: (someone please correct me if I’m wrong).

There. IANAScientist. And even I know atoms intimately, as if I were viewing them up close. But no one could possibly view an atom up close–they’re too small. So how do scientists know so much about them? Indeed, even before, say, 1945 when the first atom bomb was dropped, they had to know most of this, no? So how do scientists know so much about something they couldn’t possibly see?

Thank you in advance all who reply:)

The short answer is “experimentation”

For example, in 1909,two researchers in Rutherford’s lab conducted an experiment that shot alpha particles at thin metal foil. According to one theory, the negative charges (electrons) were spread out along the atom, and the positive charges were also uniformly distributed.

What happened in the experiment though, was that most of the particles went straight through the foil, while a very few rebounded at extreme angles. The only explanation for this was that the atom had a very tiny dense positive middle and a tiny negative charge around it. The atom was mostly empty space.

The experimenters had not “seen” an atom directly, but had managed to deduce information about the atom through indirect means via experimentation.

There are many other examples of this.

There have been electron microscope pictures that show individual atoms. I guess the next step will be to see the nucleus , if that is possible.

Just because something can’t be seen doesn’t mean we can’t observe it’s effects. A rather crude example is if you can’t see oxygen, but if you remove all of the air from a room you are going to die. So instead of physically observing protons or electrons, scientist design experiments in such a way that they interact with other particles or energy or matter and that interaction is what they observe. By carefully examining the data associated with the interaction you get clues of what the nature of the underlying particle must be. Wikipedia’s article onAtomic Theory is not to bad of a synopsis of how we arrived at current day atomic theory.

Well, we can’t see magnetism, either, but we know a lot about how magnets work because we can see a piece of iron being attracted to a magnet, and we can measure that attraction.

Even before we knew much about atoms, we had a pretty good idea of how elements and compounds worked. In the early 19th century, John Dalton observed that elements which combined to form compounds always did so in rather small whole-number ratios. So he reasoned that every element must be composed of tiny indivisible pieces that are always the same size.

By the time Mendelev was showing off his Periodic Table in the 1870s, the idea of atoms was pretty much taken for granted, though nobody could really say what they were.

Hans Geiger (of Geiger counter fame) and Ernest Rutherford conducted the famous gold foil experiment where they found that positively charged alpha particles could interact in strange ways with the atoms in a piece of gold foil, leading to the discovery that most of the mass of an atom is concentrated in a positively charged nucleus.

Of course, the Rutherford model isn’t entirely accurate either; they imagined orbiting electrons as tiny balls orbiting the nucleus like planets orbit a star. With developments in quantum physics we now know that that’s not entirely accurate (insert mumbo-jumbo about probability clouds and the Uncertainty Principle.)

Grrr … fucking magnets … .

How the fuck do they work???

In a very technical sense, magnets don’t work.

But seriously, there are many, many ways of answering that question, depending on what level of detail you want.

In the interest of avoiding an inadvertent derailing, I should point out that “fucking magnets, how do they work”, is a line from Insane Clown Posse’s Miracles.

All electrons can “see” are other electrons; that is to say, no electron can peer into the nucleus to see its structure. So electron microscopes can make very crude images of molecules, but you literally can’t “see” anything smaller.

The o.p. has a number of misapprehensions (such as the electrons physically orbiting the nucleus at high speed, or that the space in atoms is “empty”), which is not his fault but an artifact of the extremely faulty methods of conceptualizing and teaching basic science in general education. Suffice it to say that fundamentally what you think of as particles are actually distributed fields that interact at a point that is determined statistically at the time of interaction, following a set of laws we call quantum mechanics (as distinguished from classical mechanics). Some people would call this “collapsing the waveform” though there is no evidence that there is any physicality to this business of collapse; it is considered a mathematical formalism that is used because it works.

The same is true for the rest of atomic and subatomic physics; we have mathematical models that invoke things like composite bosons like protons and neutrons, made up of quarks, electrons, photons and other “gauge bosons” that “carry” force interactions. To make this more confusing, all of these particles have at least two generations of particles that have similar properties but are heavier and highly unstable, appearing only in the highest energy interactions in cosmic rays entering the atmosphere or particle accelerators. We can’t “see” any of this; instead, we take our existing model for particle physics (now unimaginatively called the “Standard Model”), look for holes in it, work out what sort of properties a particle would have to fill those holes, and then run particles into targets or each other at fantastic energies until we get decay products that match our predictions.

If the whole thing seems like a bit of a Ponzi scheme, well, you may not be terribly far off. Elegance and economy has been a guideline to identifying credible theories of physical mechanics, and the elegance and symmetry of Newtons laws of motion and gravitation and Maxwell’s equations of electrodynamics have proven out the value of such an approach. After a couple decades struggling with phenomena at the extreme of speed and gravity, special and then general relativity settled down into a very precious and useful theory that has been almost universally adopted (albeit, without still providing a fundamental answer to what “spacetime” is). But quantum mechanics and the Standard Model is a ghastly, cobbled together theory for which the primary (and perhaps only) virtue is that it works, or, at least works well enough for any practical purpose. Attempts to join quantum mechanics to other theories like electrodynamics (called quantum electrodynamics) have resulting in a generally usable theory only by taking some pretty large leaps across formal proof.

I think most physicists who stop to think about it believe that there is some further, deeper set of mechanics that are fundamentally more elegant, or at least, not as ugly as a warthog at a prom, but aside from vague and sometimes mystical ramblings about things like “the implicate and explicit order” or how Buddha had quantum mechanics figured out even though he couldn’t calculate a parabolic trajectory, no real explanation has emerged.

So, to get back to the question of the o.p., scientists know what they know about the structure of atoms by making up some wack-ass theories, throwing them up against the wall, and running experiment after experiment to see which ones stick, and then assuming that it all means something that, if not sensible, is at least consistently repeatable.

Stranger

[quote=“Stranger_On_A_Train, post:10, topic:549989”]

That is the best explanation that I have ever heard.

I have wondered the exact same thing as the OP many times and I went to a grad school in science but at least that was stuff you could see with a microscope. I am better with abstract thinking with things you can’t see now that I work in IT but I was always mystified how people in the 1900’s could use things like foil to figure out something so fundamental. I fully admit that I would be much more comfortable if they were using a lab full of really expensive equipment because that type of reasoning escapes me. However, physicists do seem to like to make some big mistakes and reverse themselves all the time as I view it from a laypersons perspective. The structure of an atom seems to be pretty solid (:rimshot) but I have to take anything beyond that on blind faith.

I think “extremely faulty methods” is too kind. Plenty of lower level school science textbooks clearly stated that the electrons orbit the nucleus. When my daughter was in high school, we put her science textbook next to one of my college physics texts and compared them. She was amazed that they would just flat out lie, and between us we could not come up with any reason for it. Her textbook didn’t even use the orbiting story to explain something else - they just wrote this incorrect statement for no purpose.

Indeed, “orbit the nucleus” is clearly the wrong term, but the alternative explanation is a bit vague without going into detail about wave/particle duality and Schrodinger’s equation: “the electrons are quite likely to probably be here [orbital], but can never be there [at a node], and may not even actually be in the nucleus at all”.

I’m sure there’s a better way to word it, but it also has to fit with the rest of the curriculum at that level - for example, dot and cross diagrams of atoms in chemistry. My A level chemistry was over 10 years ago, so I can’t remember precisely what level we went to, but I do remember we learned about the specific orbital shells (s, p, d, f) and how many electrons could go into each, just not why that was the case.

It reminds me a little of the best on-the-spot reply to a question I think I’ve ever heard. It was at a scifi convention with a panel of writers for Star Trek and someone asked, in regard to the fake tech invented to make the transporter function - “how do the Heisenberg Compensators work?” to which the immediate reply was “very well thank you.”

The primary source used for elementary school science textbooks is other elementary school science textbooks. So you start off with something with a grain of truth to it, or something which was once believed true but is now disproven, and you feed it through a game of Telephone, and what you get out the other end is an elementary school text.

I see what you did there. :slight_smile:

What **Bijou Drains **said pretty much. The experiments they do generally consist of smashing things together at higher and higher speeds and then seeing what happens. You know that’s cool even if we don’t learn anything.

All of the text book pictures are generalizations to some extent but aren’t necessarily false.

Kind of like congress and the media.

Richard Feynman relates in Surely You’re Joking, Mr. Feynman an anecdote in which he was invited to participate in a board that reviewed science and mathematics textbooks for the State Curriculum Commission for the California Board of Education (which mandated uniformity in curricula and textbooks across public school districts in the state). Aside from the blatant corruption (one volume of a series of books was delivered for selection with blank pages, as they hadn’t had time to print the text), the books themselves had very poor content. One grade school science text had a section entitled “Energy makes it go!” which explained that energy powers all sorts of things, but not what energy is, where it comes from, or why it has to be conserved.

Stranger

Is the OP thinking of the Rutherford model of the atom?

You actually can see things as small as an atom or electron I understand. I recall this physicist came up with a trick where you trap an atom or electron in a Penning trap, and using a small telescope mirror and a laser (to excite the particle into glowing) you can see the atom or electron as a dot.

You might be able to do that, but you wouldn’t be able to resolve the atom that way.