Difference between Shell, Subshell and Orbital

In atomic physics, shells, subshells, and orbitals are terms used to describe different aspects of the arrangement of electrons around an atom's nucleus. Here's a breakdown of the differences between them:

 

1. Shell:

   • Definition: A shell, also known as an energy level or principal quantum level, is a region of space around an atom's nucleus where electrons with similar energies are most likely to be found.
   • Designation: Shells are designated by integers (n = 1, 2, 3, etc.), with higher integer values corresponding to higher energy levels farther from the nucleus.
   • Capacity: Each shell can hold a maximum number of electrons, determined by the formula 2n^2, where n is the principal quantum number of the shell. For example, the first shell (n = 1) can hold a maximum of 2 electrons, the second shell (n = 2) can hold a maximum of 8 electrons, and so on.

2. Subshell:

   • Definition: A subshell is a subdivision of a shell characterized by a specific shape and energy level. Subshells represent different orbital types within a shell and are designated by letters (s, p, d, f, etc.).
   • Designation: Subshells are designated by letters that correspond to their angular momentum quantum number (l). The s-subshell has l = 0, the p-subshell has l = 1, the d-subshell has l = 2, and the f-subshell has l = 3, and so on.
   • Capacity: Each subshell can hold a maximum number of electrons, determined by the formula 2(2l + 1). For example, the s-subshell (l = 0) can hold a maximum of 2 electrons, the p-subshell (l = 1) can hold a maximum of 6 electrons, the d-subshell (l = 2) can hold a maximum of 10 electrons, and the f-subshell (l = 3) can hold a maximum of 14 electrons.

3. Orbital:

   • Definition: An orbital is a region of space within a subshell where electrons are most likely to be found. Orbitals are characterized by their shape, orientation, and energy level.
   • Designation: Orbitals within a subshell are designated by combinations of letters and numbers that represent their angular momentum quantum number (l) and magnetic quantum number (ml). For example, the s-subshell contains one s-orbital (l = 0, ml = 0), the p-subshell contains three p-orbitals (l = 1, ml = -1, 0, 1), the d-subshell contains five d-orbitals (l = 2, ml = -2, -1, 0, 1, 2), and so on.
   • Capacity: Each orbital can hold a maximum of 2 electrons, with one electron having a spin up (↑) and the other having a spin down (↓), as dictated by the Pauli exclusion principle.

 

In summary, shells represent different energy levels around an atom's nucleus, subshells represent different types of orbitals within a shell, and orbitals represent regions of space within a subshell where electrons are likely to be found. Together, they provide a hierarchical framework for describing the arrangement of electrons in atoms.

 

 

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