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Ch.12 - Solids and Modern Materials
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경
12장, 문제 52f

Repeat Exercise 12.51 for a linear chain of eight lithium atoms. (f) How does the HOMO–LUMO energy gap for this case compare to that of the four-atom case?

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1
insert step 1: Understand the concept of HOMO and LUMO. The Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) are important in determining the electronic properties of molecules.
insert step 2: Recognize that the problem involves a linear chain of lithium atoms. In a linear chain, the atomic orbitals combine to form molecular orbitals.
insert step 3: Recall that as the number of atoms in a chain increases, the number of molecular orbitals also increases, leading to a smaller energy gap between HOMO and LUMO.
insert step 4: Compare the eight-atom chain to the four-atom chain. With more atoms, the molecular orbitals are more closely spaced, which typically results in a smaller HOMO-LUMO gap.
insert step 5: Conclude that the HOMO-LUMO energy gap for the eight-atom lithium chain is expected to be smaller than that of the four-atom chain due to the increased number of molecular orbitals and closer energy levels.

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주요 개념

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HOMO-LUMO Energy Gap

The HOMO-LUMO energy gap refers to the energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). This gap is crucial in determining the electronic properties of a molecule, including its stability and reactivity. A smaller gap often indicates a greater likelihood of electronic transitions, which can affect the material's conductivity and optical properties.
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가이드 코스
01:26
Nature of Energy

Molecular Orbital Theory

Molecular Orbital Theory describes how atomic orbitals combine to form molecular orbitals that can be occupied by electrons. In a linear chain of atoms, the overlap of atomic orbitals leads to the formation of delocalized molecular orbitals, which can significantly influence the HOMO-LUMO gap. Understanding this theory helps in predicting how changes in the number of atoms in a chain affect electronic properties.
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가이드 코스
03:06
Molecular Orbital Theory

Size Dependence in Nanostructures

In nanostructures, the size and arrangement of atoms can greatly influence their electronic properties. As the number of atoms in a linear chain increases, the HOMO-LUMO energy gap typically decreases due to increased orbital overlap and delocalization of electrons. This size dependence is a key factor in materials science and nanotechnology, affecting how materials behave at the nanoscale.
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01:24
Kw Temperature Dependence
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The molecular-orbital diagrams for two- and four-atom linear chains of lithium atoms are shown in Figure 12.22. Construct a molecular-orbital diagram for a chain containing six lithium atoms and use it to answer the following questions: (c) How many nodes are in the highest-energy molecular orbital?

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Which of the following statements does not follow from the fact that the alkali metals have relatively weak metal–metal bonding? (a) The alkali metals are less dense than other metals. (b) The alkali metals are soft enough to be cut with a knife. (c) The alkali metals are more reactive than other metals. (d) The alkali metals have higher melting points than other metals. (e) The alkali metals have low ionization energies.

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교과서 질문

The molecular-orbital diagrams for two- and four-atom linear chains of lithium atoms are shown in Figure 12.22. Construct a molecular-orbital diagram for a chain containing six lithium atoms and use it to answer the following questions: (e) How many nodes are in the lowest-energy unoccupied molecular orbital (LUMO)?

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교과서 질문

Repeat Exercise 12.51 for a linear chain of eight lithium atoms. (b) How many nodes are in the lowest-energy molecular orbital? (c) How many nodes are in the highestenergy molecular orbital? (d) How many nodes are in the highest-energy occupied molecular orbital (HOMO)? (e) How many nodes are in the lowest-energy unoccupied molecular orbital (LUMO)?