General Chemistry
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When an atom absorbs a sufficient amount of energy, it is excited to a higher-energy state and a valence electron temporarily occupies a higher subshell. Provide the electron configuration of an excited argon when its outermost electron is promoted to the next available subshell.
The illustrations below show s-s or p-p orbital overlaps. Identify the illustration that depicts a π bond based on the valence bond theory.
A.
B.
C.
D.
The following illustrations show the bond vibrations for the symmetric and asymmetric stretch in methane. Which vibration will cause IR radiation to be absorbed? Note that the arrows depict the movement of atoms during the vibration.
Consider the sulfur dioxide (SO2) molecule which has the same bond vibrations as carbon dioxide. Which of the following bond vibration in sulfur dioxide will cause IR radiation to be absorbed?
The structure of annulene, C10H10, is shown below. Focusing only on the π bonds (σ bonds are not included), the π molecular orbital of annulene can be described by the following energy diagram:
Identify which are the bonding, antibonding, and nonbonding molecular orbitals.
Consider a π2p for a certain type of MO diagram. Identify whether the bonding orbital or the antibonding orbital will have a higher energy. Justify your answer.
Which of the following describes the difference in electron distribution between a bonding MO and an antibonding MO?
Draw a diagram that illustrates the position and geometry of the p orbitals in ozone (O3). Using a localized valence bond model for σ bonds and a delocalized MO model for π bonds, explain the bonding in the compound.
The last step in the formation of the hybrid orbitals of a carbon atom is illustrated in the orbital diagram below. Which of the following statements most accurately sums up what happened prior to the step depicted in the diagram?
(a) three electrons fill up the 2p atomic orbital
(b) the promotion of an electron into the 2p atomic orbital from the 2s orbital
(c) the 2s orbital becomes three orbitals
What labels do we use for the two MOs shown that are part of the molecular orbital energy-level diagram for MOs constructed from 2s atomic orbitals?
Draw a molecular orbital diagram for a chain containing 5 sodium atoms and identify the number of molecular orbitals.
Determine the number of delocalized electrons in the pi system of formate.
Determine if the lone pair in the molecule below exhibits delocalization.
Determine if the pi bond in NO3– exhibits delocalization.
Identify if the statement below is true:
Bonding orbitals can only be filled in pairs since a bond needs two electrons.
If there are electrons in the antibonding orbital, it means that a bond does not exist between the atoms.
Give the illustration for two atoms that each has three 2p orbitals. Determine the number of bonding orbitals and the type of MO that can be constructed from the two sets of 2p orbitals.
If the He2+ ion was excited by light to move an electron:
a) there would be more antibonding electrons than bonding electrons In the excited state.
b) the light would excite the electron from a higher energy MO to a lower energy MO.
c) the light would excite the electron from a lower energy MO to a higher energy MO.
Determine the type of MO present in the given contour representation of a molecular orbital
a. σ type
b. π type
Which atomic orbital/s is involved in the creation of the given contour representation of a molecular orbital?
Draw the resulting bonding and antibonding molecular orbital from the combination of the following:
a) 2px + 2px
b) 2py + 2py
Identify the difference between the two.
Draw the resulting bonding and antibonding molecular orbital from the combination of 2sp3 + 2sp3.
Draw the resulting molecular orbital by the 2s + 2s constructive interference and identify the type of MO.
Draw the orbital diagram of OCl2 without hybridization and highlight the bonding electrons.
Draw the 3D representation of the molecule showing orbital overlap and identify the expected bond angle from the unhybridized orbitals.
It was experimentally determined that the bond angle is 110.9°.
What is the difference between the expected bond angle based on valence bond theory and the experimental measurement?
Which of the following statements is true about the overlap of two s atomic orbitals in terms of the molecular orbital theory?
Identify the molecular orbital electron configuration which does not represent an excited state.
Identify the molecule with one or more localized π (pi) bonds.
Classify each of these molecular orbital representations as constructed from two s atomic orbitals or two p atomic orbitals.
Classify each of the following molecular orbital representations as bonding or antibonding MO.
HOMO is the abbreviation for the highest occupied molecular orbital of a molecule and LUMO is the abbreviation for the lowest unoccupied molecular orbital. The difference in energy between the HOMO and LUMO can be determined by taking the electronic absorption (UV-visible) spectrum of the molecule. The HOMO-LUMO transition corresponds to molecules going from their ground state to their first excited state. Identify the orbital transition that the lowest energy peak of O2 corresponds to.
Which of the following statement is true regarding the comparison of the energy gap between the HOMO-LUMO for straight six-chain lithium atoms and straight eight-chain lithium atoms?
Which of the following statements is correct based on the given molecular orbital diagram for an eight lithium atom chain?a. There are no nodes in the highest-energy occupied molecular orbital (HOMO)b. There are 3 nodes in the highest-energy occupied molecular orbital (HOMO)c. There are 4 nodes in the highest-energy occupied molecular orbital (HOMO)d. There are 6 nodes in the highest-energy occupied molecular orbital (HOMO)
Which of the following statements is correct based on the given molecular orbital diagram for a six lithium atom chain?
a. There are no nodes in the lowest-energy unoccupied molecular orbital (LUMO)
b. There are 3 nodes in the lowest-energy unoccupied molecular orbital (LUMO)
c. There are 5 nodes in the lowest-energy unoccupied molecular orbital (LUMO)
d. There are 7 nodes in the lowest-energy unoccupied molecular orbital (LUMO)
The three structures shown below are for naphthalene, phenanthrene, and chrysene. These three are derivatives of benzene in a way that the six-membered rings of benzene are fused along the edges. Naphthalene and anthracene are colorless solids while chrysene is a golden-yellow crystalline solid. What can be inferred about the HOMO-LUMO gap in these molecules using this information?
The overlap of two 1s atomic orbitals in hydrogen, as shown in the diagram below, results in the formation of two molecular orbitals: One bonding (σ1s) orbital and one antibonding (σ*1s) orbital. Absorption of a high-energy photon can excite an electron from the bonding molecular orbital to the antibonding molecular orbital. Assuming that this transition is a HOMO-LUMO transition, identify the HOMO in hydrogen.
The overlap of two 1s atomic orbitals in hydrogen, as shown in the diagram below, results in the formation of two molecular orbitals: One bonding (σ1s) orbital and one antibonding (σ*1s) orbital. Absorption of a high-energy photon can excite an electron from the bonding molecular orbital to the antibonding molecular orbital. Assuming that this transition is a HOMO-LUMO transition, identify the LUMO in hydrogen.
Molecules that have small energy gaps between their HOMO and LUMO orbitals appear brightly colored. Which one of the following has a smaller HOMO-LUMO energy gap: Congo red, which is a red dye, or naphthol yellow S (a yellow dye).