atomic structure

[lord molly]

just started my a-levels, and doing chemistry. in GCSE we were told that atoms had "rings" of electrons orbiting them, all in perfect circles, with 2 in the first then up to 8 in all the others.

now i have been told that there are difrent types of orbitals, following elipses and flower like patters in "energy" levels, and that there are now three types, S, P, and D orbitals.


im so confused could n e budding scientist explane to me the core basics of this new theory.


thanks sooooooooooo much


lord molly

[shammydodger]

Boy, do I remember the frustration you must be feeling. To get into the first A level class and be told to forget much of what you were told at O level because it was too simplistic a model!

One of the first concepts you will have to try to come to terms with is that electrons don't have any truly defined "paths of travel", for want of a better term, around the nucleus of an atom. These orbitals that you are being "introduced to describe the space around a nucleus where one would, in all probability, expect to "find" these electrons at any moment if one could observe them. It's based on a mathematical treatment by quantum mechanics. Happily, you won't need to concern yourself with the nasty mathematical formulae (that delight is saved for the masochists who go onto study chemistry and/or physics at degree level).

As one moves further away from the nucleus, the volume of space in which electrons may be expected to be found becomes larger and more complicated (hence the elaboration from sphere, to "dumbell" to "clover" as one goes from s to p to d orbitals. Incidentally, there are f orbitals beyond the d orbitals but, as I seem to recall, you are only required to know the first 30 elements in detail so ought not to be concerned with f orbitals. Thank heaven for small mercies!

There are further things to explain, of course, but you need to get away from thinking that electrons go around in neatly defined capsules of space, holding hands, all at the same distance from the nucleus. On the atomic level, things don't behave in ways that are familiar to us at macroscopic level. You even need to get away from the simplistic idea that electrons are like little, solid balls of matter. So, try to get used to the idea that these orbital thingies are merely "probability volumes" in which one would expect to "find" a particular electron. I think the often quoted probability is 95%, but I'll stand corrected on that point.

[lord molly]

wooo, thanks, it just seems odd that you lean "the right way" in GCSE, the get told it is wrong, then you lean a different "right way"


thatnks


lord molly

[theprof]

Brilliant explanation shammydodger - full marks.

[mibn2cweus]

Simplified models are useful for explaining simpler concepts. The important thing to remember is that they are just that, models.

basic concepts and evolving science

[Dr. Chaos]

shammydodger, I read in an old physics book that the electrons travel around their orbits at about 150,000 miles per second. At that speed in such a small space as the shells, they are darn near everwhere in the shell at practically the same time. Is this information correct ? The book was from the 1940's