Name: electron regions in atomic orbitals
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 44 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry and Physics

IPC.7

IPC.7.E

Atomic Orbitals

电子云最密集的区域 电子最有可能被发现的地方 可以用原子轨道来描述。原子轨道的形状 由角动量量子数 l 决定。回想一下，l 的值是基于主量子 数，n 的—l 的可能值的范围是从 0 到 n-1。当 n 大于 1 时，会存在多个子级。l 的每个值对应于 s、p、d 或 f 轨道。最低能量轨道是 1-s 轨道。这是一个球对称的轨道。1-s 轨道的 概率密度揭示了电子 最有可能在原子核中被发现。然而，考虑到质子和电子之间的 静电力—这不太可能。用概率密度乘以 半径为 r 的薄球壳的体积 则更具代表性。在离原子核 r 远的薄壳内 找到电子的总概率 为径向分布函数。对于氢，在离原子核 52.9 皮米处找到电子的 可能性最大。因此，氢的 1-s 原子轨道的形状 是球形的，半径为 52.9 皮米。2-s 和 3-s 轨道也是球形的。它们更大并且有节点。在一个节点上，找到电子的概率为零。n 等于或大于 2 的主能级 也包含三个 p 轨道。这些轨道是叶状的并且在核心处有一个节点。它们的取向用 m-l 的值来描述。这三个 p 轨道相互正交。n 等于或大于 3 的主能级 也有五个 d 轨道。具有三叶草形状的 d 轨道 有四个电子密集的叶和两个垂直的节点 平面。其中一个 d 轨道稍有不同。f 轨道有更多的叶和节点。这些轨道存在于 n 等于或 大于 4 的主能级。当你把这些轨道一个接一个叠加在一起时，会出现一个大致呈球形的形状。这就是为什么原子通常被表示为球体的原因。

原子轨道

原子轨道表示电子中最有可能存在的原子中的三维区域。径向分布函数表示在距原子核的距离r处的薄壳中找到电子的总概率。原子轨道具有不同的形状，这些形状由角动量量子数 l 决定。轨道通常是用边界表面绘制的，包围了云的最密集区域。
 
 角动量量子数是一个整数，可以取值 l = 0、1、2＆hellip ;、 n ＆ndash; 1.主量子数为1（ n = 1）的轨道只能有一个 l （ l = 0）值，而主量子数2（ n = 2）允许 l = 0和 l = 1。 > l 定义一个子外壳。
 
 l = 0的轨道称为 s 轨道，它们构成了 s 子壳。值 l = 1对应于 p 轨道。对于给定的 n ， p 轨道构成一个 p 子壳（即，如果 n = 3）。 l = 2的轨道称为 d 轨道。 l = 3、4和5的轨道是 f ， g 和 h 轨道。 ; 
 
 最低能量轨道是1 s 轨道。这是一个球对称的轨道。 1 s 轨道的概率密度（＆psi; 2 ）表示电子最有可能在原子核处发现。但是，给定质子和电子之间的静电力，这不能准确地表示电子将驻留的位置。取而代之的是使用径向分布函数，它是在给定半径 r 的情况下在轨道上找到电子的总概率图。通过将概率密度乘以半径为 r 的薄球形壳的体积，可以找到径向分布函数。对于氢的1 s 轨道，径向分布函数在原子核处的值为零，该值在52.9皮米处增加到最大值，然后随 r 的增加而减小。</ >
 
 距原子核有一定距离，在该距离处找到位于特定轨道的电子的概率密度为零。换句话说，波函数＆psi; 的值在此距离处为此轨道为零。这样的 r 值称为径向节点。轨道中的径向节点数为 n ＆ndash; l ＆ndash; 1.对于2个 s 轨道，其中 n = 1，有一个径向节点，而3 s 轨道具有两个径向节点。 
 
 n n = 2或更高的每个主能级包含三个 p 轨道。这三个 p 轨道有两个裂片，其结点位于原子核上。 p 轨道在空间中的方向由 m l 的值描述。三个 p 轨道相互垂直（正交）。较高的 p 轨道（3 p ，4 p ，5 p 和更高）具有相似的形状，但是尺寸更大，并带有更多的径向节点。
 
 n = 3或更高的主能级包含五个 d 轨道。这些轨道中的四个由三叶草形状组成，带有四个电子致密波瓣。有两个垂直的节点平面在原子核处相交。在这些节点平面上，电子密度为零。 d 轨道之一的形状略有不同，并且有两个沿 z 轴定向的瓣，并且在 xy 中有一个甜甜圈形环。飞机。 n = 4或更大的主能级包含七个形状复杂的 f 轨道。这些轨道比 d 轨道具有更多的节点和波瓣。
 
 <img alt =“ Figure1” src =“ https://www.jove.com/files/core/CDNSource/lessons/983/983Image 1.png” style =“ width：700px; ” /> 
 
 图1：代表性 s ， p ， d 和 f 轨道。
 
 这些不同形状的原子轨道代表了可能在其中发现电子的三维区域。所有轨道共同构成一个大致球形，这就是为什么原子通常表示为球形的原因。
 
 本文改编自<a href="https://openstax.org/books/chemistry-2e/pages/6-3-development-of-quantum-theory"> Openstax，化学 2e，第6.3节：量子理论的发展。</a>

原子轨道表示原子中电子最有可能存在的三维区域。径向分布……

Education

教育

JoVE Core

Chemistry

化学

Electronic Structure of Atoms

原子的电子结构

KEY TERMS AND CONCEPTS

关键术语与概念

electron regions in atomic orbitals

Electron regions in atomic orbitals show where an electron is most likely to be found in an atom. These three-dimensional regions are often drawn as boundary surfaces around the densest part of the cloud.

The shape of an orbital depends on the angular momentum quantum number, l. This value can range from 0 to n - 1, where n is the principal quantum number. For n = 1, only l = 0 is allowed. For n = 2, both l = 0 and l = 1 are allowed.

Orbitals with the same value of l form a subshell. The l = 0 orbitals are s orbitals, and they make up s subshells. The l = 1 orbitals are p orbitals, which form a p subshell such as 3p when n = 3. The l = 2 orbitals are d orbitals. The l = 3, 4, and 5 orbitals are called f, g, and h orbitals.

The lowest-energy orbital is the 1s orbital. It is spherically symmetric. The probability density, ψ², suggests that an electron is most likely found at the nucleus. But this does not fully match electron behavior. The radial distribution function gives the total probability of finding an electron at a distance r from the nucleus. It is found by multiplying the probability density by the volume of thin spherical shells.

For the 1s orbital of hydrogen, the radial distribution function is zero at the nucleus. It rises to a maximum at 52.9 picometers and then decreases as r increases. Some distances from the nucleus have zero probability density for a given orbital. These points are called radial nodes. The number of radial nodes is n - l - 1. A 2s orbital has one radial node, and a 3s orbital has two.

Each principal level with n = 2 or more contains three p orbitals. Each p orbital has two lobes and a node at the nucleus. Their orientation in space is described by m_l. The three p orbitals are mutually perpendicular. Higher p orbitals, such as 3p, 4p, and 5p, have the same general shape but are larger and contain additional radial nodes.

Principal levels with n = 3 or more contain five d orbitals. Four of them have a cloverleaf shape with four electron-dense lobes. They also have two perpendicular nodal planes that meet at the nucleus. The fifth d orbital has two lobes along the z-axis and a donut-shaped ring in the xy plane.

Principal levels with n = 4 and greater contain seven f orbitals. These orbitals have complex shapes with more nodes and lobes than d orbitals. Together, s, p, d, and f orbitals help explain why atoms are often drawn as spheres, even though the electron regions inside them have distinct shapes.

Electron Regions in Atomic Orbitals

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Electron Regions in Atomic Orbitals

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