📚 Atomic Shells, Subshells, and Orbitals | 原子层、亚层与轨道
Understanding the arrangement of electrons in atoms is fundamental to explaining chemical bonding and periodicity. The concepts of shells, subshells, and orbitals provide a structured way to describe the spatial distribution and energy of electrons, moving beyond the simple Bohr model.
理解原子中电子的排布是解释化学键和周期性的基础。电子层、亚层和轨道的概念为描述电子的空间分布和能量提供了一种结构化的方式，超越了简单的玻尔模型。
1. Introduction to Quantum Numbers | 量子数简介
In the quantum mechanical model, each electron in an atom is described by a set of four quantum numbers: principal (n), azimuthal (l), magnetic (ml), and spin (ms). Together they define the energy, shape, orientation, and spin of an electron. The shell, subshell, and orbital hierarchy emerges from the first three quantum numbers.
在量子力学模型中，原子中的每个电子由四个量子数描述：主量子数 (n)、角量子数 (l)、磁量子数 (ml) 和自旋量子数 (ms)。它们共同定义了电子的能量、形状、方向和自旋。电子层、亚层和轨道的层次结构正是从前三个量子数衍生而来。
2. Principal Quantum Number and Shells | 主量子数与电子层
shell (n=1) is closest to the nucleus and has the lowest energy. As n increases, the shell' s higher. Shells are often labelled with letters: K (n=1), L (n=2), M (n=3), N (n=4), etc.
主量子数 n 可以取任何正整数值（n = 1, 2, 3, ...）。它决定了电子所处的主能级，即电子层。第一层 (n=1) 最靠近原子核，能量最低。随着 n 增大，电子层到原子核的平均距离增加，能量也更高。电子层常用字母标记：K (n=1)、L (n=2)、M (n=3)、N (n=4) 等。
3. Subshells: s, p, d, f | 亚层：s、p、d、f
s and 2p; the third shell has 3s, 3p, and 3d; and the fourth shell has 4s, 4p, 4d, and 4f.
每个电子层又可划分为亚层，由角量子数 l 表示。l 的取值范围是 0 到 n-1。当 l=0,1,2,3 时，亚层分别标记为 s, p, d, f。因此，第一层 (n=1) 只有一个亚层 (1s)；第二层 (n=2) 有 2s 和 2p；第三层有 3s, 3p, 3d；第四层有 4s, 4p, 4d, 4f。
| l value | Subshell letter | Number of orbitals | Max electrons |
|---|---|---|---|
| 0 | s | 1 | 2 |
| 1 | p | 3 | 6 |
| 2 | d | 5 | 10 |
| 3 | f | 7 | 14 |
The energy of a subshell depends on both n and l. In a multi-electron atom, subshells with the same n but higher l have slightly higher energy: s < p < d < f.
亚层的能量取决于 n 和 l。在多电子原子中，n 相同但 l 较大的亚层能量略高：s < p < d < f。
4. Orbitals: Shapes and Orientation | 轨道形状与方向
An orbital is a region of space around the nucleus where there is a high probability (usually >90%) of finding an electron. Each orbital is defined by a unique set of n, l, and ml quantum numbers. The magnetic quantum number ml ing 0. Thus, an s subshell (l=0) has one orbital; a p subshell (l=1) has three orbitals (ml 0, +1); a d subshell (l=2) has five orbitals; and an f subshell (l=3) has seven orbitals.
轨道是原子核周围空间中电子出现概率很高（通常 >90%）的区域。每个轨道由一组独特的 n、l 和 ml 量子数定义。磁量子数 ml 取从 -l 到 +l 的整数值，包括 0。因此，s 亚层 (l=0) 有一个轨道；p 亚层 (l=1) 有三个轨道 (ml = -1, 0, +1)；d 亚层 (l=2) 有五个轨道；
Published by TutorHao | IB Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图