Electron configuration

Electron Configuration is a term used in Atomic Physics and Quantum Mechanics to describe the arrangement of electrons in an atom. It is fundamental to understanding the chemical behavior of atoms and molecules.

Overview

The electron configuration of an atom is the representation of the arrangement of electrons distributed among the orbitals of an atom. Electrons are placed into available orbitals, sublevels, and levels. This arrangement is often depicted graphically as an electron configuration diagram.

Quantum Numbers

The electron configuration of an atom is determined by its Quantum Numbers. These are sets of numerical values which give acceptable solutions to the Schrödinger wave equation for the hydrogen atom. There are four quantum numbers: the principal quantum number (n), the azimuthal quantum number (l), the magnetic quantum number (m), and the spin quantum number (s).

Aufbau Principle

The Aufbau Principle states that in the ground state of an atom, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. For example, the 1s shell is filled before the 2s subshell is occupied.

Hund's Rule

Hund's Rule states that every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin.

Pauli Exclusion Principle

The Pauli Exclusion Principle states that no two electrons in an atom can have identical values for all four of their quantum numbers. This principle explains the entire structure of the periodic table and the existence of the four quantum numbers.

Electron Configuration Notation

The electron configuration of an atom can be represented by a notation that consists of the atomic symbol, the energy level number, the type of orbital and the number of electrons in the orbital. For example, the electron configuration of lithium would be written as Li 1s² 2s¹.

See Also

• Atomic Structure
• Periodic Table
• Quantum Mechanics
• Atomic Physics

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