Wikipedia:Reference desk/Archives/Science/2015 March 15

= March 15 =

Does it matter which way you apply a Nyloc nut?
When fastening a Nyloc nut on a screw, does it matter whether the nylon side points forward or backwards? &mdash; Sebastian 02:27, 15 March 2015 (UTC)


 * The nylon is not threaded. Unless the Nyloc nut was reused, which is not recommended, I think one would have difficulty getting the Nyloc nut started onto the bolt. This is just a guess. I hope someone familiar with the product weighs in. Bus stop (talk) 02:52, 15 March 2015 (UTC)


 * Yes, the nylon portion is not pre-threaded. Sebastian, are you proposing to run a bolt through from the "proper" end to cut or press correctly aligned threads into the nylon, and then to attempt to engage these threads to run the bolt in from the other direction?  If successful, you are facing some reuse safety issues on your first use.
 * Also, the end away from the nylon has the better seating / bearing surface. -- ToE 03:04, 15 March 2015 (UTC)


 * Sorry about being unclear. I think your answers already give me the answer I was looking for: The metal side is the "proper" side; I agree that it's harder to put the nylon side on a bolt first, presumably because it has no precise guidance for the thread. And no, I wasn't proposing a two-stage process as in ToE's first paragraph. Thanks! &mdash; Sebastian 03:38, 15 March 2015 (UTC)

numbers that stands for part of sublevels in electron configuration
What is the explanation for the negative numbers that stands for part of sublevels in electron configuration? (-2,-1,0,1,2)5.28.179.219 (talk) 07:48, 15 March 2015 (UTC)
 * That isn't a standard notation for Electron configuration - a typical example is 1s22s22p63s1, the ground state of the sodium atom. Where did you see the notation in your question? Tevildo (talk) 09:31, 15 March 2015 (UTC)


 * These numbers look to be the magnetic quantum number. It describes the space quantization of the angular momentum of the orbiting electron. The + number means that the angular momentum vector is closest in direction to the field direction, and a negative means it is pointing in the maximum backwards direction. 0 is perpendicular. Graeme Bartlett (talk) 11:32, 15 March 2015 (UTC)
 * Another possibility that these are valences, or oxidation states, see e.g. List of oxidation states of the elements -- 87.151.33.39 (talk) 12:26, 15 March 2015 (UTC)


 * I think that they refer to valencies, -1 refers to a lack of an electron that would make up the full outer shell, 0 would mean that the atom has the full complement for its outer shell, while +2 means that there is an excess of electrons. DISCLAIMER..Chemistry is not my strength. I'd go with Tevildo's answerRead-write-services (talk) 04:15, 16 March 2015 (UTC)
 * Given electrons have negative charge, it's not common to say that having excess electrons would be a positive-sign electronic situation (compare to 87.151.33.39's answer that is standard for concepts of atomic charge). But given the question is about identifying sublevels, Graeme is right on with explanation and links for this standard meaning. DMacks (talk) 04:25, 16 March 2015 (UTC)


 * The OP is talking about the magnetic quantum number for the l=2 (i.e. d sublevel) state. Without going to deep into the mathematics, (most of which I forget anyways), the quantum numbers are solutions to the Schrödinger equation that produce the various quantized energy states an electron can exist in.  To simplify the equation, the quantum numbers are always integers, and they follow a rather simple set of rules.  For example, n must be a positive integer, while the l = 0 --> -n for each value of n (thus, at n = 1, l = 1, at n = 2, l = 0 or 1, at n = 3, l = 0 or 1 or 2).  The m values (the third quantum number) can equal -l --> +l for any value of l, so if l = 1, m = -1, 0, +1.  Two of the quantum numbers, the n (energy level) and l (energy sublevel) are of different energy (thus a 1st level electron has less energy than a second level electron, while a 2p electron has more energy than a 2s electron).  However, all of the m values for any given l are equal in energy, so the designation of a particular orbital as m = -2 or m = -1 is arbitrary.  There's some conventions that say define the orientation of a specific orbital with a specific m values, but these conventions require one to pick an arbitrary direction to define the alignment of the orbitals to.  The - has no physical meaning per se, except as a sign convention for directionality.  -- Jayron 32 05:13, 16 March 2015 (UTC)

Could hydrogen and oxygen form a ring molecule?
Could a molecule be something like H-O-H-O-...-connect to the first H atom? Would this molecule be stable? Llaanngg (talk) 16:31, 15 March 2015 (UTC)
 * The ring that you describe appears to have the hydrogen exhibiting a valence of 2, and hydrogen only has one native electron, and doesn't have a valence, in the usual sense, of 2, so that, no, the molecule wouldn't be stable, and wouldn't exist as a molecule at all. If, on the other hand, you are asking whether the hydrogen atoms could be attracted to nearby oxygen atoms by hydrogen bonding, then that is one of the characteristics of water, which isn't a ring molecule, but consists of H2O molecules bound to each other (weakly compared to the strength of the internal bonds).  Robert McClenon (talk) 16:45, 15 March 2015 (UTC)


 * Such a configuration would be an electron deficient cycle of Three-center two-electron bonds, whereby each hydrogen will have two electrons, and each oxygen will have seven electrons. It would also be a polyradical, with each oxygen having an unpaired electron. This would mean that the molecule is extremely reactive and unstable with respect to rearrangement, or decomposition. Plasmic Physics (talk) 06:49, 16 March 2015 (UTC)


 * You may be interested in water dimer. Graeme Bartlett (talk) 09:45, 16 March 2015 (UTC)


 * The structure of ordinary ice has loops like this ... but the hydrogens always prefer a position closer to one oxygen, further from the other. What's interesting though is that you could take those structures and reverse them, i.e. there must be some absolutely stupendous information storage capacity in ice if you could read and write bits of data by moving the hydrogens around the ring.  I think. Wnt (talk) 13:57, 16 March 2015 (UTC)

Basic species question
Suppose a group of organisms, a "species", can interbreed with each other to produce fertile offspring. Is it generally supposed that the group should be able to reproduce and produce fertile offspring with the group's most recent common ancestor?--Leon (talk) 18:36, 15 March 2015 (UTC)
 * That isn't an easy question. See species problem to see the complexity of what is considered a species.  Part of the question would be how long ago the group had a single common ancestor.  Thousands of years ago?  Tens of thousands of years?  Hundreds of thousands of years?  Has the species been under selective pressure since it began radiating from a common ancestor, so that all of its modern members differ from the common ancestor?  Sometimes it isn't even easy to define a "common ancestor", as the discussion of mitochondrial Eve and Y-chromosomal Adam should indicate.  Questions involving what is a species are often more complicated than one might think.  Robert McClenon (talk) 18:52, 15 March 2015 (UTC)
 * I think the answer is not necesarily. Try ring species perhaps mightbe relavant? Vespine (talk) 23:10, 15 March 2015 (UTC)
 * Actually i'm going to change my answer to "this is a malformed question". Have you read Most recent common ancestor? It took me several goes around before I started understanding it. Neither "species" nor MRCA hass a very "fixed" definition. Most recent common ancestor of a single species, could by definition be of that species, so would be able to breed with the species. BUT on the other hand, a single isolated population of a species COULD undergo a speciation event (that's how "it" happens after all), then the population that was isolated would have a common ancestor that could no longer breed with the "new" species, but then is the MRCA of the new species, the same as the MRCA of the "old" isolated species, or is there a "new" MRCA from when the speciation event occurred? Vespine (talk) 21:59, 16 March 2015 (UTC)
 * I'm not sure how to answer your last question. But my gut says surely that the new species has a new MRCA. How could it not be? Where am I going wrong?--Leon (talk) 13:16, 17 March 2015 (UTC)
 * The other thing to think about is simple timing. If I have a set of N individuals (not necessarily a species), then as N gets larger, the MRCA becomes almost certainly dead - so no breeding is possible without a time machine. I'm not sure, but I suspect sympatric speciation could lead to a situation where the MRCA of species A could not make viable offspring with species A, even if we had a time machine. Island biogeography may well have some examples of this. SemanticMantis (talk) 14:41, 17 March 2015 (UTC)
 * I assumed the OP meant with access to a time machine. I doubt there are any species (beyond bacteria perhaps) where the MCRA is still "alive". In any case, i think the OP has more of a problem with semantics than genetics. I would recommend the OP read The Ancestor's Tale, I think it explains certain concepts about evolution very well, specifically concepts relating to common ancestry. Vespine (talk) 22:10, 17 March 2015 (UTC)