Parmi les configurations électroniques suivantes, distinguez...

Parmi les configurations électroniques suivantes, distinguez celles qui représentent un état fondamental ou un état excité, ainsi que celles qui sont impossibles. 1) Classez-les dans ces trois catégories. 2) Donnez l'état fondamental correspondant aux états excités. 3) Indiquez la raison qui rend certaines impossibles. A) K, L, $3 \mathrm{~s}^2, 3 \mathrm{p}^2, 4 \mathrm{~s}^1$ B) K, L, M, $4 \mathrm{~s}^2, 4 \mathrm{p}^6, 4 \mathrm{~d}^1, 5 \mathrm{~s}^2$ C) K, L, M D) $1 s^2, 2 s^2, 2 p^5, 2 d^1$ E) K, L, M, $4 \mathrm{~s}^2, 4 \mathrm{p}^6, 4 \mathrm{~d}^{10}, 4 \mathrm{f}^{14}, 5 \mathrm{~s}^2, 5 \mathrm{p}^6, 5 \mathrm{~d}^{10}, 6 \mathrm{~s}^2, 6 \mathrm{p}^3$ F) K, L, $3 \mathrm{~s}^2, 3 \mathrm{p}^6, 3 \mathrm{~d}^{11}, 4 \mathrm{~s}^2, 4 \mathrm{p}^2$ G) K, L, $3 \mathrm{~s}^2, 3 \mathrm{p}^6, 3 \mathrm{~d}^{10}, 3 \mathrm{f}^{14}, 4 \mathrm{~s}^2, 4 \mathrm{p}^2$ K) $\mathrm{K}, 2 \mathrm{~s} \square, 2 \mathrm{p}$ आ.ाी L) K, L, 3s $\square$

Parmi les configurations électroniques suivantes, distinguez celles qui représentent un état fondamental ou un état excité, ainsi que celles qui sont impossibles.
1) Classez-les dans ces trois catégories.
2) Donnez l'état fondamental correspondant aux états excités.
3) Indiquez la raison qui rend certaines impossibles.
A) K, L, $3 \mathrm{~s}^2, 3 \mathrm{p}^2, 4 \mathrm{~s}^1$
B) K, L, M, $4 \mathrm{~s}^2, 4 \mathrm{p}^6, 4 \mathrm{~d}^1, 5 \mathrm{~s}^2$
C) K, L, M
D) $1 s^2, 2 s^2, 2 p^5, 2 d^1$
E) K, L, M, $4 \mathrm{~s}^2, 4 \mathrm{p}^6, 4 \mathrm{~d}^{10}, 4 \mathrm{f}^{14}, 5 \mathrm{~s}^2, 5 \mathrm{p}^6, 5 \mathrm{~d}^{10}, 6 \mathrm{~s}^2, 6 \mathrm{p}^3$
F) K, L, $3 \mathrm{~s}^2, 3 \mathrm{p}^6, 3 \mathrm{~d}^{11}, 4 \mathrm{~s}^2, 4 \mathrm{p}^2$
G) K, L, $3 \mathrm{~s}^2, 3 \mathrm{p}^6, 3 \mathrm{~d}^{10}, 3 \mathrm{f}^{14}, 4 \mathrm{~s}^2, 4 \mathrm{p}^2$
K) $\mathrm{K}, 2 \mathrm{~s} \square, 2 \mathrm{p}$ आ.ाी
L) K, L, 3s $\square$

Key Concepts

Pauli Exclusion Principle

The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers. This rule limits the number of electrons that can occupy a single orbital (two per orbital with opposite spins) and is fundamental in validating or refuting configurations that might seem to violate electron occupancy limits.

Electron Shells and Subshells

Electron shells, designated by principal quantum numbers, and their respective subshells (s, p, d, f, etc.) determine the structure and energy hierarchy in an atom. Each shell and subshell has a specific capacity, and understanding these divisions is essential to discerning whether a given electron configuration is physically possible, corresponds to a ground state, or represents an excited state.

Aufbau Principle

The Aufbau principle is the guideline that electrons fill atomic orbitals in order of increasing energy, starting with the lowest energy orbital and moving upward. This principle is crucial for determining the ground state configuration and understanding why certain excited states occur when electrons are displaced from their expected positions.

Ground State

The ground state is the configuration in which an atom’s electrons reside in the lowest possible energy levels, obeying the Aufbau principle. It represents the most stable and lowest energy arrangement, making it the natural state of an atom when it is not under the influence of external energy sources.

Electron Configuration

This refers to the arrangement of electrons among the available atomic orbitals, following specific quantum mechanical rules. It is a systematic description of how electrons populate shells, subshells, and orbitals based on energy levels, and it provides the foundation for understanding the chemical properties of elements.

Excited State

An excited state occurs when one or more electrons are promoted to higher energy orbitals than those occupied in the ground state. This higher energy arrangement is less stable and temporary, often reverting back to the ground state by releasing energy, typically in the form of electromagnetic radiation.

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