TheSigma和Pi分子轨道之间的关键区别is that sigma molecular orbital forms from the overlapping ofatomic orbitals沿着核对轴的轴向正向方向,而PI分子轨道是由平行方向上原子轨道重叠的。
Sigma and pi molecular orbitals are two types of molecular orbitals that contribute to the actual structure of a chemical compound. The molecular orbitals are responsible for the formation ofsingle and doubleor triple bonds, respectively.
内容
1.Overview and Key Difference
2.What are Molecular Orbitals
3.What are Sigma Molecular Orbitals
4.什么是PI分子轨道
5.Sigma与PI分子轨道的表格形式
6.Summary – Sigma vs Pi Molecular Orbitals
What are Molecular Orbitals?
原子结合在一起形成分子。当两个原子靠近形成一个分子时,原子轨道重叠并合并为分子轨道。新形成的分子轨道的数量等于组合原子轨道的数量。此外,分子轨道围绕原子的两个核,电子可以在两个核周围移动。与原子轨道相似,分子轨道最大包含2个具有相反旋转的电子。
Moreover, there are two types of molecular orbitals asbonding molecular orbitals and antibonding molecular orbitals。成键分子轨道包含电子the ground state, while antibonding molecular orbitals contain no electrons in the ground state. Furthermore, electrons may occupy antibonding orbitals if the molecule is in an excited state.
What are Sigma Molecular Orbitals?
Sigma molecular orbitals are types of hybrid orbitals that form from the overlapping of two atomic orbitals from head-to-head along the internuclear axis. Typically, the first covalent bond between two atoms is always a sigma bond. Overlapping of two atomic orbitals in the inter-nuclear axis forms a sigma covalent bond. In a sigma molecular orbital, the electron density at the middle of the molecular orbital is high if the two atoms from which the atomic orbitals overlap are identical.
在以氢为例时,Sigma分子轨道是由来自每个氢原子的两个1S原子轨道的重叠形成的。我们可以将此Sigma键缩写为σ。在这里,共享电子密度直接发生在沿键轴的键合原子之间。与单独原子的稳定性相比,这使两个键合原子与粘结电子之间的相互作用更加稳定。通常,Sigma键是在两个原子之间形成的第一个键。
什么是PI分子轨道?
Pi molecular orbitals are types of hybrid orbitals that form from the overlapping of two atomic orbitals in the parallel direction. Here, the bonding electron density occurs above and below the internuclear axis. Further, we cannot observe electrons at the bonding axis. This type of interaction between two atoms forms a more stable arrangement than the stability of separated free atoms. Usually, electrons tend to occupy this type of molecular orbitals when enough electrons are present in the atoms. Pi molecular orbitals always form as second or third molecular orbital formation regarding the bonding of two atoms because sigma molecular orbital is the first molecular bond to form between two atoms.
Moreover, the number of atoms that are contributing to a p atomic orbital of the pi system is always equal to the number of pi molecular orbitals present in a chemical bond. Typically, the lowest pi molecular orbital has zero vertical nodes existing. Here, the successive pi molecular orbitals get one additional vertical node upon increasing the energy. We can abbreviate a pi molecular orbital as π.
Sigma和Pi分子轨道有什么区别?
Sigma and pi molecular orbitals are two types of molecular orbitals that contribute to the actual structure of a chemical compound. The key difference between sigma and pi molecular orbitals is that sigma molecular orbital forms from the overlapping of atomic orbitals in a head-to-head direction along the internuclear axis, whereas pi molecular orbitals form from the overlapping of atomic orbitals in a parallel direction.
The following infographic lists the differences between sigma and pi molecular orbitals in tabular form for side by side comparison.
Summary – Sigma vs Pi Molecular Orbitals
A molecular orbital is a type of orbital that forms from the overlapping of atomic orbitals. The key difference between sigma and pi molecular orbitals is that sigma molecular orbital forms from the overlapping of atomic orbitals in a head-to-head direction along the internuclear axis, whereas pi molecular orbitals form from the overlapping of atomic orbitals in a parallel direction.
Reference:
1.“”What Is a Sigma Molecular Orbital?”BYJUS,2020年12月24日。
1.“”15.3: Pi Molecular Orbitals of Benzene。”Chemistry LibreTexts,libretexts,2020年7月14日。
Image Courtesy:
1.“”Hydrogen Molecule” ByChiralJon(CC由2.0)via Flickr
2. “Mo图Pi轨道” By V8rik at en.wikipedia(CC BY-SA 3.0)via Commons Wikimedia
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