What is Diatomic molecule: Definition and 29 Discussions

Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements. The prefix di- is of Greek origin, meaning "two". If a diatomic molecule consists of two atoms of the same element, such as hydrogen (H2) or oxygen (O2), then it is said to be homonuclear. Otherwise, if a diatomic molecule consists of two different atoms, such as carbon monoxide (CO) or nitric oxide (NO), the molecule is said to be heteronuclear. The bond in a homonuclear diatomic molecule is non-polar.

The only chemical elements that form stable homonuclear diatomic molecules at standard temperature and pressure (STP) (or typical laboratory conditions of 1 bar and 25 °C) are the gases hydrogen (H2), nitrogen (N2), oxygen (O2), fluorine (F2), and chlorine (Cl2).The noble gases (helium, neon, argon, krypton, xenon, and radon) are also gases at STP, but they are monatomic. The homonuclear diatomic gases and noble gases together are called "elemental gases" or "molecular gases", to distinguish them from other gases that are chemical compounds.At slightly elevated temperatures, the halogens bromine (Br2) and iodine (I2) also form diatomic gases. All halogens have been observed as diatomic molecules, except for astatine and tennessine, which are uncertain.
Other elements form diatomic molecules when evaporated, but these diatomic species repolymerize when cooled. Heating ("cracking") elemental phosphorus gives diphosphorus, P2. Sulfur vapor is mostly disulfur (S2). Dilithium (Li2) and disodium (Na2) are known in the gas phase. Ditungsten (W2) and dimolybdenum (Mo2) form with sextuple bonds in the gas phase. Dirubidium (Rb2) is diatomic.

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  1. S

    I Selection Rules for a Diatomic Molecule?

    Hello! I have a question about selection rules and electronic transitions of a diatomic molecule: I can't find a good explanation about that, and there's so much confusion about the right rules to use. I studied that on Bransden-Joachain's "Physics of atoms and molecules", but there (to whom...
  2. LCSphysicist

    Diatomic molecule at a constant temperature

    A diatomic molecule ##D_{2}## in ##30K##, in ##t=0##, is in the state ##| \psi (0) \rangle = \frac{1}{\sqrt{26}}(3 | 1,1 \rangle + 4| 7,3 \rangle + | 7,1 \rangle )##, where the kets denote states ##| l,m \rangle##. Use ##\frac{\hbar}{Ic4\pi}=30.4cm^{-1}##. Obtain ##| \psi (t) \rangle ## I...
  3. M

    A Dissociation of a diatomic molecule containing Al

    Hello! Is there any diatomic molecule containing Al (or even a molecular ion), which upon dissociation from a given electronic level, leaves behind Al as a neutral atom? Any reference is appreciated. Thank you!
  4. K

    A Centrifugal distortion of a diatomic molecule

    Hello! Is it possible for the centrifugal distortion constants (D, H and so on) of a diatomic molecules to be negative? It looks like for high enough vibrational distortions they can be negative, but I don't think I've ever seen that in practice so I was wondering if there is something...
  5. B

    A Power induced shift in rotational transitions for a diatomic molecule

    Hello! I am analyzing some data from some rotational transitions between 2 electronic energy levels in a diatomic molecule. I noticed that for different runs that covered the same regions, the peaks we observe are shifted with respect to each other when the power of the laser driving the...
  6. F

    Momentum of intertia for a dihydrogen molecule

    I don't know if the value for distance between protons given in the homework is right (##d = 74.14 pm##). Indeed, on the following link : https://brainly.in/question/7147660 , they take a distance equal to ##d = 4\times10^{-10} m##. In all cases, the same formula is applied ...
  7. MathematicalPhysicist

    How to simplify the diatomic molecule Hamiltonian using an expansion?

    Homework Statement I have the diatomic molecule hamiltonian given by: $$-\hbar^2/(2\mu)d^2/dr^2+\hbar^2\ell(\ell+1)/(2\mu r^2)+(1/4)K(r-d_0)^2$$ Now it's written in my solutions that if we put: $$K\equiv 2\mu \omega_0^2, \hbar^2\ell(\ell+1)/(2\mu d_0^4)\equiv \gamma_{\ell} K, r-d_0\equiv...
  8. Pushoam

    Degrees of freedom of a diatomic molecule

    Homework Statement Homework EquationsThe Attempt at a Solution Considering the molecule as collection of two spherical atoms whose centers are joined such that they touch each other, Then, as a rigid body the system has 6 degrees of freedom and around the axis joining the two centers, the...
  9. A

    A Diffusion of Hydrogen through Molybdenum alloy

    I have been preforming experiments to study the diffusion of Hydrogen through Molybdenum. According to Sievert's law diatomic molecules would diffuse as atoms. But according to my experiments I notice that the flux of hydrogen is directly proportional to the pressure of hydrogen and not to the...
  10. thegirl

    I Finding the vibrational partition function of a diatomic molecule

    Hi, How did they break down the following summation? When finding the vibrational partition function ofa diatomic molecule it was approximated that the energy levels of the vibrational part of the diatomic molecule were harmonic and therefore the energy equation for a harmonic oscillator was...
  11. samst

    Hund's cases for diatomic molecules

    Dear All, May anyone please advise me to the following questions in case of diatomic molecules: 1. How do we choose which Hund's case ((a), (b), or (c)...) that best describes a particular diatomic molecule? 2. How can we deduce from Hund's cases molecular electronic states (2s+1)ΛΩ (e,g...
  12. M

    Is ionization potential a function of internuclear distance?

    Has there been a study which concludes that the ionization potential of a diatomic molecule depends on the internuclear distance? For example, let this molecule interact with an EM wave, and hence after the disturbance the molecule vibrates. If subsequently I send an ionizing radiation with...
  13. Runei

    What causes the repulsive force in diatomic molecules?

    Hello, I'm working here with a model for a diatomic molecule. The potential is modeled as two finite wells. For a given distance between the wells, the energy of the ground state will be minimized. If you move the "atoms" closer to each other, the energy rises, and if you move them away from...
  14. A

    X(t) of a diatomic molecule with given v_0

    Homework Statement Two identical carts (of mass m) are free to move on a frictionless, straight horizontal track. The masses are connected by a spring of constant k and un-stretched length l_{0}. Initially the masses are a distance l_{0} apart with the mass on the left having a speed v_{0} to...
  15. A

    Why is there a sin^2(theta) factor in the diatomic molecule Hamiltonian?

    Homework Statement I have to find the hamiltonian for a diatomic molecule, where the molecule can only rotate and translate and we supose that potencial energy doesn't change.Homework Equations The Attempt at a Solution Okey so I used Spherical coordinate system such as the kinetic energy of...
  16. C

    How to graph potential energy for 2 atoms in diatomic molecule w/ 3 unknowns

    Homework Statement The potential energy of two atoms in a diatomic molecule is approximated by U(r)=a/r^12 - b/r^6, where r is the spacing between the atoms and a and b are positive constants. Find the force F(r) on one atom as a function of r. Make two graphs one of U(r)...
  17. V

    Diatomic molecule vibrational frequency

    Homework Statement Calculate the ratio of frequencies of oscillations of the molecules H2 and HD. Homework Equations f=(1/2pi)(k/m)^0.5 f=frequency k=spring constant m= mass or reduced mass The Attempt at a Solution I got (2/6)^0.5 but the given answer is (4/3)^0.5. I...
  18. H

    Short Answer SHM of diatomic molecule

    Homework Statement Two identical atoms in a diatomic molecule vibrate as harmonic oscillators. However, their center of mass, midway between them, remains at rest. 1)Show that at any instant, the momenta of the atoms relative to the center of mass are p and -p 2)Show that the total...
  19. A

    Sketching a Phase Portrait for Diatomic Molecule

    Homework Statement I have to sketch a phase portrait (in phase space) for a system which is a diatomic molecule. The effective potential is equal to a potential that is attractive at long range and repulsive at short range plus the centrifugal barrier. It basically looks like a Morse...
  20. B

    Vibrational frequency of diatomic molecule

    Homework Statement Using specific heat data for a nitrogen molecule, estimate then vibrational frequency of the diatomic molecule Homework Equations C= 3N_a k = 3R The Attempt at a Solution unable to attempt a solution
  21. N

    Rotational energy of diatomic molecule

    Hi, I consider harmonic model of diatomic molecule: two atoms connected with a massless rod. Let one axis be along the rod, other two perpendicular to it. Let rotational velocity have components only trough perpendicular axes. In one book it is said that rotational energy of such diatomic...
  22. H

    3D isotropic harmonic oscillator vs. diatomic molecule

    The Hamiltonian of the diatomic molecule is given by H = p1^2 / 2m + p2^2 / 2m + 1/2 k R^2, where R equals the distance between atoms. Using this result, given in standard texbooks, I keep geting C = 9/2 kT instead of 7/2 kT for heat capacity. I've traced down my problem to the potential energy...
  23. H

    Quantum Mechanics on Diatomic Molecule: Info Sources

    Does anyone know where I can find information about using quantum mechanics on the diatomic molecule (E.g. Lectures on YouTube or just notes)? Thanks.
  24. G

    Potential-energy function of diatomic molecule

    Hi there all, I have this problem which I have issues with; there's some stuff I need to do in C and any help would be much appreciated. For V(o) = 36 i need to find the ground state energy and normalised ground state function using matrix methods. I am allowed to use Matlab to find the...
  25. J

    Rotation Spectrum of a diatomic molecule (QM)

    Homework Statement In the rotation spectrum of 12C16O the line arising from the transition l = 4 -> 3 is at 461.04077GHz, while that arising from l = 36 -> 35 is at 4115.6055GHz. Show from these data that in a non-rotating CO molecule the intra-nuclear distance is s ~ 0.113 nm, and that the...
  26. L

    Quantized Vibrations in Diatomic Molecules | HyperPhysics

    Is this saying that the frequency of vibrations in a diatomic molecule is quantized? http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/hosc.html#c1
  27. P

    QM perturbation theory: rigid diatomic molecule

    Homework Statement The Hamiltonian for a rigid diatomic molecule is H_0 = {L^2 \over {2I}} where I is the moment of inertia of the molecule. (a) What are the lowest four energy states of this system? (b) An external electric field is applied, leading to a perturbation H_1 = ED\cos\theta...
  28. Q

    How Do Rotational Spectra Reveal Molecular Structure?

    We have Heteronuclear diatomic molecules with atomic masses m1 and m2 and an internuclear distance R have rotational energy eigenvalues EJ = BJ(J + 1) , J = 0, 1, 2, . . . when they are considered as a rigid rotor. The rotational constant is given by B = h^2/2µR^2 with the reduced mass µ =...
  29. quasar987

    A diatomic molecule rotating about it's axis of symetry

    In my thermo text, they consider a diatomic molecule that is rotating about the axis joining the two atoms (also the axis of symetry) and make a quantum argument involving the energy levels of a rigid rotator to conclude that kT<<\Delta E for this particular degree of freedom. But isn't this...