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What is the bond order of He2? How to turn a weak acid into a strong acid. Answer. The electrons in antibonding orbitals cancel (and exceed) the stabilization resulting from electrons in bonding orbitals. For example, uranium-238 isotope ( 238 92 U) disintegrates to emit α-rays (consisting of doubly charged helium ion, He2 + ). And the explanation given is quite plausible to me. Can You Describe the Smell of Ammonia to Me? report. The value of the bond order gives the number of electron pairs being shared between two atoms in a chemical bond. Therefore, He2 molecules are not predicted to be stable (and are not stable) in the lowest energy Expert Answer: According to Molecular Orbital theory, only those molecule can exists which have net positive bond order while the molecules with negative or zero bond order will not exists. c. Is unstable molecule with bond order of zero and it is diamagnetic. He2 is not possible. 3- H 2 is the most stable because it has the highest bond order (1), in comparison with the bond orders (1/2) of H 2 + and H 2-. According to molecular orbital theory, He2 cannot exist as a stable diatomic molecule due to there being 2 bonding and 2 antibonding electrons. It can only exist at very low cryogenic temperatures. Excited state doesn't have lower energy! – will exist, explain many properties – for example why O 2 is a paramagnetic diradical – and identify the important frontier molecular orbitals (FMOs). For a "standard" molecule - one that doesn't have filled antibonding orbital - that would be true. 18 vertical columns. Please explain reasons. Postby Nhi Vo 3A » Tue Oct 25, 2016 7:08 pm, Postby Chem_Mod » Tue Oct 25, 2016 11:31 pm, Users browsing this forum: No registered users and 2 guests. 6. Suppose you're correct, then why would stabler excited He2 molecules, Because in the ground state the antibonding effect of the antibonding orbitals gets higher than in the excited molecule - and it gets high enough for the molecule to become unstable. The helium dimer is a van der Waals molecule with formula He 2 consisting of two helium atoms. The σ 1s bonding and antibonding orbitals will be full. 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Dihelium does not exist. So, the bond order is zero. This is a question in "Chemical Principles, 6th Edition, Steven Zumdahl": I'm sorry you are not finding help at the moment. Since there are as many bonding electrons as as antibonding, there is no net bond. O 2 + is more stable than O 2-.Because According to molecular orbital theory O 2 + has 15 electrons &it has one electron in antibonding orbital. Therefore, C2- has a stronger bond as it is more stable and harder to pull an electron away from it. I mean, what's the reason the stable, low-energy excited state would spontaneously drop electron to transform to the unstable, high-energy ground state? He2+: 3 valence → BO=1/2 → stable He2: 4 valence → BO=0 → unstable. Noboru, the cat below, is the administrator of this unstable place. Which nuclear particle is identical to an He2+ ion? was last updated on 28th December 2020 Therefore, the 8 electrons would fill up both outer orbitals, the s and p orbitals, while for C2- it would only fill up the 1s orbital and have 2 electrons in the 2s orbital. Question starts telling you it IS the experimental fact, doesn't it? How could Helium gas be nonexistent? e. Is stable molecule with bond order of 1 and it is diamagnetic Please don't post links to copyrighted material, I have replaced it with a link to acs abstract. Well, it doesn't say anything about configuration, but it tells us the molecule exist. Two atomic orbitals combined to form a molecular orbital which have bonding, non bonding ,anti bonding orbital s. In Be _ 1s2 2s2 has 2bonding &2anti bonding orbital s. Bond … To answer the question, you must construct a molecular orbital (MO) diagram for the hypothetical He 2 molecule. That's where you are wrong. Is unstable molecule with bond order of 1/2 and it is diamagnetic. In physics, metastability is a stable state of a dynamical system other than the system's state of least energy.A ball resting in a hollow on a slope is a simple example of metastability. Two electrons total, both occupy the sigma orbital, two more electrons in bonding than antibonding orbitals, the compound is stable. d. Is stable molecule with bond order of 3 and it is paramagnetic. Download Free solutions of NCERT chemistry Class 11th from SaralStudy. ... Isotopes with even numbers of protons and neutrons are more stable than those with odd numbers of protons and neutrons. Calculating the bond order results in 0. Draw the molecular orbital diagram for each and explain your answer. All of the following can act as a semiconductor except The spontaneous decay of an unstable heavier nucleus with a simultaneous emission of certain radiations is called radioactivity. Its negative ionic character suggests that it could be even less stable. molecular orbital diagram of O 2 + Electronic configuration of O 2 + In the case of O 2-17 electrons are present &3 electrons are present in antibonding orbitals. Answer and Explanation: 1420 MHz--- the emission frequency of cold hydrogen gas. Use molecular orbital theory to determine whether He2 or He2+ is more stable. 71% Upvoted. If the ball is only slightly pushed, it will settle back into its hollow, but a stronger push may start the ball rolling down the slope. With the help of molecular orbital theory show that Ne2 cannot exist as stable species . Asked by Aashna Anith Kumar | 4th Feb, 2014, 11:50: PM. SaralStudy helps in prepare for NCERT CBSE solutions for Class 11th chemistry. save. a. I am afraid I won't be of much help when it comes to books - the ones I can suggest will be in Polish, so of no use for you. , Using Standard Molar Entropies), Gibbs Free Energy Concepts and Calculations, Environment, Fossil Fuels, Alternative Fuels, Biological Examples (*DNA Structural Transitions, etc. All of the following can act as a semiconductor except (a) Ga (b) Ge (c) Si (d) GaAs (e) GaN x2. However, antibonding effect of the excited antibonding orbital is weaker than the antibonding effect of the antibonding orbital in the ground state - so once the antibonding orbital gets excited, its overall effect on the molecule stability gets lower and the molecule becomes stable. Although there is a bonding influence from the two bonding electrons, there is an antibonding influence from two antibonding electrons. For a bond to be stable, the bond order must be a positive value. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. b. Faster, greener way of producing carbon spheres, Discovery boosts theory that life on Earth arose from RNA-DNA mix, New chemistry for controlling the volume of liquid in volumetric additive manufacturing, http://pubs.acs.org/doi/abs/10.1021/ed084p860, Roughly 20% of the molecules in the air are oxygen molecules. Two He atoms might then form a He2 molecule with configuration (σ1s)2(σ1s*)2 which is stabler than the two excited He atoms. Di helium cation (He2+) possess three electron over all two are present in bonding sigma molecular orbital and are paired and one electron in antibonding sigma orbital which is unpaired. 3 comments. Eg: He + He; same mixing as above. Diprotons are not stable; this is due to spin-spin interactions in the nuclear force, and the Pauli exclusion principle, which forces the two protons to have anti-aligned spins and gives the diproton a binding energy greater than zero. Is my reasoning on this correct: According to MO theory, H2 + will be more stable than He2 + because while they both have same bond order, He2 + has anti bonding electrons which destabilizes the molecule. Polarity in water molecule and electronegativity of oxygen in that molecule. If number of electrons more in antibonding orbital the molecule become unstable. The larger the bond order, the more stable the molecule. But we are talking about molecule that is not a standard one - it has a filled antibonding oribtal, which makes is completely unstable in the ground state. This thread is archived. Be2- is more stable that Be2, and Be2 is more stable than Be2+. In the periodic table, there are 18 groups i.e. Since diatomic noble gas molecules, such as He2 and Ne2, do not exist. Be2 is stable and paramagnetic, but Li2 is unstable. The net result is a less stable molecule than if the electrons remained in their respective \(1s\) atomic orbitals. On moving from group 1 to group 2 i.e. Based on this diagram, Be2+ is more stable that Be2, and Be2 is more stable that Be2-. The bond that holds this dimer together is so weak that it will break if the molecule rotates, or vibrates too much. Which type of radiation emitted by radioactive nuclei is similar in mass to a helium atom? share. Is a stable molecule with bond order is 3 and it is diamagnetic. A few years ago, this extremely weakly bonded system has been finally observed, although some controversies still remain on the inter- pretation of the experimental results [6]. Why is he2+ stable? It has a higher energy, which is what makes the antibonding effect weaker. hide. The ground state MO electron configuration for He2 is (σ1s)2 (σ1s*)2 giving a bond order of 0. Removing green copper oxides with Electrolysis, chemicals, etc. From above discussion hope you have guessed that only dihydrogen H2 is diamagnetic species. Be2 is more stable than either Be2- or Be2+. with this explanation, excited-state configuration (...) seems stabler than ground-state configuration (...) while it's not the case. It was to my understanding that He2 = Helium Gas = what we used to put in party balloons? Never heard about it. This chemical is the largest diatomic molecule—a molecule consisting of two atoms bonded together. Noble Gas. Is there any additional information you can share with us? New comments cannot be posted and votes cannot be cast. According to J.D Lee, compounds with fraction bond number are unstable--Li2+ BOND ORDER = 0.5 Li2 BOND ORDER =1 Hence Li2+ must be unstable than Li2 but then why Li2 is more stable than Li2+. Use the following MO diagram for Be2, Be2+, and Be2-. Ga bc must have the possibility of averaging 4 valence electrons. Do you have any source for that? In other words, no bond can be sustained between two He atoms according to … The substance emits high energy particles or rays from its unstable nucleus. Using molecular orbital theory, state why He2 not a stable molecule? Diatomic Species by Molecular Orbital Theory. Even rather simple molecular orbital (MO) theory can be used to predict which homonuclear diatomic species – H 2, N 2, O 2, etc. So, O 2 2+ is more stable than O 2 2- ion because of high bond order of O 2 2+ ion. The electron configuration of dihelium: If the molecule He2 were to exist, the 4s electrons would have to fully occupy both the bonding and antibonding levels, giving a bond order of zero. As a result, the He 2 molecule does not have a lower energy than two widely separated helium atoms and hence has no tendency to form. 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