Molecular Definition and 583 Threads

Show aging effects at the molecular level https://www.nature.com/articles/d41586-024-03105-x

Since SO3 has an expanded octet structure, the central S should form three double bonds with O, meaning S forms 3 pi bonds in total. However, after hybridisation of S, there are less than three unpaired electrons in unhybridised p-orbitals of S. How can S form 3 pi bonds when there aren’t enough...

This letter in PhysRevLett describes molecular dynamics simulations to investigate the underlying factors that drive osmosis. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.97.024501 Copy on Internet Archive ...

Hello, I am fairly new to the world of molecular spectroscopy, so I apologize for any ignorance on my part. For the last few months, I've been working on a diatomic spectral simulation tool and have reached a point where I want to incorporate more advanced theory to model complex interactions in...

Are physical atoms really arranged in hexagon patterns, or is that some sort of way to represent them for illustrations in textbooks and in science articles? (i.e. atoms aren't actually arranged in any hexagon pattern)

why dna absorbs best at 260nm?

Hello, I am having some trouble finishing this problem from my textbook and would like some insight on the problem. We are looking for the molecular formula of a hydrocarbon. So, if we let x = number of C atoms and y = number of H atoms then we need to find ##C_xH_y##. From the problem...

Hello! I saw many paper extracting the magnetic dipole and electric quadrupole moments of the nuclei by performing RF/microwave spectroscopy on the rotational levels of a molecule. However, I can't seem to find paper measuring higher order moments. For example, the magnetic octupole moment has...

I suppose there is a database for that, but I can't find it. Could anyone send here a link?

Starting with a), I have learnt that the potential energy function has a minimum at the equilibrium distance ##a##. So at the equilibrium distance the derivative of the potential energy function should equal zero: ##\begin{align} V'(a)&=-\frac{4A}{a^5}+\frac{B}{a^2}=0 \nonumber \\ \iff...

Molecular speed of gas is generally $$v=\sqrt{\frac{3RT}{M}},$$where R is gas constant and M is molecular mass. Can we use this formula for the air as well, when the air is a mixture of different gasses?

I thought it was trigonal bipyramidal, with iodine forming 5 bonds with 5 fluorine atoms. Actually, iodine has another lone electron pair, making it square planar. Is there a reason why iodine has another lone pair when it has already exceeded the octet rule? And how would I predict how many...

Princeton U. has a great intro to molec. behav. w. sound, but neither there or elsewhere have I found much on the initial acceleration phase. Is it assumed that movement over these nano-distances is already happening at c - and then there is just more of it ? How can a little stone you drop on a...

##K = \frac{N}{m} = \frac{3eV}{bondlength^2} = \frac{4.806*10^-19 J}{(2*10^-10)^2} = 12.015## Then I know that ##H = \frac{1}{2}mωx^2 ## where ## k = mω^2 ## and also ##H=ħω(n+\frac{1}{2}) ## Therefore, ## \frac{1}{2}kx^2 = ħω(n+\frac{1}{2})## Solving for n, ## n = \frac{1/2kx^2}{ħω} -...

Hello What experiment or observation shows that for atoms, molecules or masses of gas, there is attraction in the sense of Newton's law (universal attraction)? Bernadette

Hello. As an assignment, I have to explain the total molecular Hamiltonian. Problem is, I can't find it anywhere in my book (Atkins, Physical Chemistry: Quanta, Matter, and Change, 2nd Edition), even when I access the index for "Hamiltonian -> polyatomic molecules". They do give the electronic...

I am sure this is an elementary question; I'm just trying to clarify some points that were poorly explained to me years ago in secondary school. I know that a full answer would involve solving Schrödinger's equation etc., but keeping this on the level of valence electrons,...) I was confused by...

Hello! Is there a place where I can find the expressions for higher order terms of molecular parameters (in particular the spin rotational parameter, ##\gamma##)? All the papers I find just show them up to second order. Thank you!

Hello! Can we have molecular transitions (not restricted to electric dipole) that change the multiplicity of the electronic level i.e. ##2S+1##. For electric dipole that is strictly forbidden. For magnetic dipole, we have a term in the operator of the form ##S\cdot B## and assuming the B is...

Hello! I see that in experiments at facilities like ISOLDE, they produce molecular beams at energies of tens of keV. If I understand it right, they first create the molecule as a positive ion, and using electric fields (and maybe magnetic for mass selection) they take the particle out of the...

Good morning, I read on the internet that a molecular cloud contains denser part, I also read that a molecular cloud start to collapse according the Jeans law If it's the full cloud collapsing what is happening to these denser parts ? and after collapsing how the fragmentation occurs ? In fact...

Is the following molecular formula for Sugar can be written as H22C12O11 or O11C12H22 or O11H22C12 or C12O11H22 or H22O11C12 instead of C12H22O11? Logically they can be written as mentioned above? If Not, Why? There can be many more examples similar to above.

Hello! If I have a beam of positively (single) charged molecular ions (they can be either bunched on continuous), and I want to end up with a decelerated (close to stationary) ensemble of neutral molecules (e.g. to trap them in a MOT trap), is there a way to reduce the velocity of the charged...

Hello! I noticed in several papers describing high resolution vibrational measurements in diatomic molecules, such as this one, in the conclusion section, that they mention that we can search for new forces (or deviation from gravity inverse square law) between the 2 nuclei by measuring well...

Molecular potential energy of hydrogen in dependence with atomic distance for bonding orbital is given by picture below. We can see that at large distances force between atoms is attractive and potential energy drops to minimum which corresponds to bond energy and length. This part of the...

I don't see how isolate m or M. That is, how to get rid of <v^2> which is how I wrote the average of v2

Hello! I am reading some stuff about the effective hamiltonian for a diatomic molecule and I have some questions about relating the parameters of these hamiltonian to experiment and theory. From what I understand, one starts (usually, although not always) with the electronic energy levels, by...

Hello everyone I am trying to solve the following question from the book Analytical Chemistry 7th edition by Gard D. Christian - Page 164 Example 5.17 My problem is when I calculate the molecular weight of Pb(NO_3)_2 I get 331.2 g/mol but in the book they get 283.2 g/mol . Could you explain...

So, doing an experiment with my daughter (making similar size balloons filled with carbon dioxide and air), and verifying that the CO2 balloon fell quite noticeably faster due to higher molecular weight; I later noticed that the CO2 balloon shrank clearly faster than the air balloon. This was...

Suppose we have a molecule A-A and a molecule A-B . And we want to compare the differences in energy of the different molecular orbitals for example the 1s antibonding orbital with the 2s bonding orbital.How can we do that?

I'd like approximate the noise floor of an ultrasonic air transducer starting from molecular vibrations. Simply put, if I treat atmospheric air as an ideal gas and I confine each air molecule to exist in a volumetric cube with a square face ##A_\mathrm{face}##, then I approximate the number of...

Moles are proportional to volume. There is 1000 cm3 of gas (carbon dioxide gas plus water vapour) after the reaction, and 200 cm3 of water vapour after the carbon dioxide has been absorbed. Therefore, there is 800 cm3 of carbon dioxide. Since the stoichiometric ratio of carbon dioxide to the...

I am from physics background and I need some background in Genetics to learn Genomic Data Science. So, can people here suggest some youtube playlist ? I have not studied biology for a long time , so no idea about biology. Suggestions welcome Thanks

Hey guys, I decide I need to learn the mathematics of molecular-orbital theory, to build on the qualitative approach of my chemistry coursee. To do this I also first need to study single-electron systems and then many-electron systems, the Born-Oppenheimer approximation, and relevant topics...

I've searched high and low for an answer to my question and I can't find a thing. Let's say I blow into the end of a tube. The opposite end is connected to a reed; when the air hits the reed, the reed vibrates and I can hear a sound. The harder I blow, the louder the reed sounds. I've tested...

Hi all. Feynman writes: https://www.feynmanlectures.caltech.edu/I_46.html https://en.wikipedia.org/wiki/Brownian_ratchet Does emerging of temperature differences supposedly violate the 2nd law? (yes?) As soon as a temperature difference occurs, e.g. a Carnot process could work...

Hello, The sigma $(\sigma)$ molecular orbitals are symmetrical around the bond-axis while pi $(\pi)$ molecular orbitals are not symmetrical. For example, the linear combination of 1s orbitals centered on two nuclei produces two molecular orbitals which are symmetrical around the bond-axis. Such...

mx remets to mass in gram of the compost x nx remets to moles of the compost x nTot remets to the total moles x remets to the additional moles of D2 I considered the molar mass: MH2 = 2u MHD = 3u MD2 = 4u 10 = mH2 + mHD + mD2 10 = nH2*2 + nHD*3 + nD2*4 10 = nTot + 0.9nTot + 0.8nTot nTot =...

The equation can be seen in the picture. I was assuming it was an Sn2 reaction given the polar aprotic solvent and strong nucleophile. For b), I assumed that the question asked me to draw the orbitals as shown above (as opposed to orbital diagram) because it asked me to identify the HOMO and...

Hello! I have some data for rovibrational transitions between a ##X^2\Sigma^+## and ##A^2\Pi_{1/2}## and I need to extract the molecular parameters (e.g. B, D, ##\gamma## etc) for the 2 levels. I tried pgopher for a while, using Hund case B and A for the 2 states, respectively. However it...

hi guys i am a the third year undergrad student and in this 2nd semester in my collage we should start taking quantum mechanics along with molecular physics , our molecular physics professor choose a book that we are going to take which is " molecular physics by wolfgang Demtroder " when i...

How can I calculate diameter of a molecule

This article from Science Advances (probably not open access, an AAAS publication) has described a complex and interesting molecular mechanism (a nano-bio-molecular machine). A rotary motor in the cell membrane (driving mechanisms unknown) spins a gear that pushes a "tread" along a track imbeded...

I don't understand how to use output from an NPT molecular dynamics simulation to compute a thermodynamic derivative. I need to compute this (where "d" is a partial derivative, "T" is a subscript that means, "at constant temperature," and "E" is internal energy): -(dE/dV)T I have a simulation...

Will finish B.S. in molecular biology in May. Have found asking vague questions about where to go/apply to next are pretty unhelpful. I believe that going through indexes of interesting research is the closest I can get to finding a place to advance myself and be happy in. here is an example...

Hello! I have some data from a molecular spectroscopy experiment, containing vibrational and rotational spectra, and I want to fit the peaks with Voigt profiles (one for each peak) in order to obtain the centers of the peaks. Do you know any software suitable for this kind of fit? I usually use...

In molecular dynamics people use periodic boundaries to confine particles being simulated. I read here that they are used to simulate large "infinite" particle systems. How can I know that the periodic boundary is simulating actual molecular outcomes for a finite particle system that had a large...

I am interested in showing a visualization of water molecules in a time-varying electric/magnetic field as part of my PhD work. I would like something like this visualization: , but with an external time-varying field applied. At first, I thought of simply animating water molecules...

Answer given is " The molecule could be trigonal pyramidal or T shaped, but could not be trigonal planar." I am confused as the shape of BF3 is trigonal planar...

In figure. Why F use 2P rather than 2S to bonding in HF MO model.