Two possible electron configurations for an Li atom are shown here. (c) In the absence of an external magnetic field, can we say that one electron configuration has a lower energy than the other? If so, which one has the lowest energy?

Verified step by step guidance

1. Identify the electron configurations given for the Li atom. Typically, the ground state electron configuration for Lithium (Li) is 1s^2 2s^1.
2. Understand that the energy of an electron configuration depends on the shells and subshells in which electrons are located. Electrons in lower shells (closer to the nucleus) generally have lower energy.
3. Consider the Pauli Exclusion Principle and Hund's Rule to determine if the given configurations are in their lowest possible energy states. The Pauli Exclusion Principle states that no two electrons in an atom can have the same set of four quantum numbers, and Hund's Rule states that electrons must occupy every orbital singly before any orbital is doubly occupied.
4. Analyze if the electrons are placed in the lowest available energy states according to the Aufbau principle, which states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.
5. Determine which configuration has electrons in the lowest energy states and thus represents the lowest energy configuration for the Li atom in the absence of an external magnetic field.

Key Concepts

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. For lithium (Li), which has three electrons, the configurations can vary based on how these electrons occupy the available energy levels. Understanding the specific arrangement of electrons is crucial for determining the atom's energy state.

Energy Levels and Stability

Electrons occupy specific energy levels, with lower levels being more stable. When electrons fill orbitals, they tend to occupy the lowest available energy states first, following the Aufbau principle. A configuration that minimizes energy is generally more stable, which is essential for comparing the energy of different configurations.

Pauli Exclusion Principle

The Pauli Exclusion Principle states that no two electrons in an atom can have the same set of quantum numbers. This principle influences how electrons are arranged in orbitals, affecting the overall energy of the atom. Configurations that adhere to this principle while minimizing energy will be more stable and thus lower in energy.