Question

What is electron configuration? Describe the roles that the Pauli exclusion principle and Hund's rule play in writing the electron configuration of elements.

Short answer

Electron configuration is the distribution of electrons in an atom or molecule's atomic or molecular orbitals. Pauli exclusion principle ensures that each electron in an atom occupies its own unique state, which is identified by a unique set of quantum numbers. Hund's rule states that every orbital in a subshell is individually occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin. These principles help determine how atoms achieve the lowest energy and thus the most stable states.

Step-by-step solution

Defining Electron Configuration

Electron configuration refers to the distribution of electrons of an atom or molecule in atomic or molecular orbitals. It provides a means to understand the structure of shells and their make up. In elements, electrons populate the orbitals, subshells, and shells in a particular manner.

Understanding the Pauli Exclusion Principle

The Pauli Exclusion Principle, stated by Wolfgang Pauli, establishes that no two electrons within a given atom can share the same set of quantum numbers. This principle is fundamental in the arrangement of electrons into shells and subshells in an atom. It basically ensures that each electron in an atom occupies its own unique state, which is identified by a unique set of quantum numbers.

Explaining Hund's rule

Hund's rule, named after Friedrich Hund, is used when populating electron orbitals with electrons. It states that every orbital in a subshell is individually occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin. This is principally applied when writing out the electron configurations of elements, resulting in the most stable configuration (least energy) for an atom. In real-world terms, it's like people preferring to have their own seats before sharing.

Applying the concepts to Electron Configuration

When writing the electron configurations of elements, first distribute the electrons in different orbitals based on the increasing order of energy levels according to the Pauli exclusion principle ensures each electron is unique. Then apply Hund's rule to fill each orbital in a subshell singly before any is doubly occupied, and all electrons in singly occupied orbitals have the same spin to ensure the atom reaches the least energy and the most stable state.