The aufbau principle states that, in determining the lowest energy electron configuration for an element,
a. all electrons must be paired as much as possible
b. only two electrons can be placed in a single orbital
c. electrons in a subshell of orbitals should occupy all
orbitals singly with parallel spins before the electrons are paired
d. electrons should occupy the orbitals lowest in energy
e. no two electrons can have the same spin
f. no two electrons can have the same set of four quantum numbers
The Correct Answer and Explanation is :
The correct answer to your question on the aufbau principle is:
d. electrons should occupy the orbitals lowest in energy
Explanation
The aufbau principle is a fundamental concept in quantum chemistry, particularly when configuring the electrons of an atom in their lowest energy states. This principle serves as a guideline for determining the electron configuration of elements in their ground state. It is essential for understanding how electrons fill atomic orbitals.
The principle’s name, “aufbau,” is derived from the German word for “building up” or “construction.” It suggests that electron configuration for atoms builds up by progressively filling electron orbitals from the lowest energy level to higher ones. Here’s a breakdown of how it works:
- Lowest Energy First: Electrons occupy the orbitals that have the lowest energy first. This is because electrons naturally tend to exist in the most stable (lowest energy) state possible. For example, in a neutral hydrogen atom, the single electron goes into the 1s orbital, the lowest available energy level.
- Pauli Exclusion Principle and Hund’s Rule: While the aufbau principle dictates the order in which orbitals are filled, the Pauli Exclusion Principle and Hund’s Rule describe how electrons fill these orbitals. The Pauli Exclusion Principle states that no two electrons can have the same set of four quantum numbers, which leads to the requirement that each orbital can hold a maximum of two electrons with opposite spins. Hund’s Rule states that electrons must occupy all orbitals in a subshell singly before any orbital is doubly occupied, and all electrons in singly occupied orbitals should have the same spin to maximize total spin.
- Orbital Energy Levels: The typical order of filling orbitals based on their increasing energy levels is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, and so forth. This order can be predicted through (n+l) rule where ‘n’ is the principal quantum number and ‘l’ is the azimuthal quantum number, determining the shape of the orbital.
The aufbau principle helps in predicting how the electrons are structured in atoms, which is crucial for understanding chemical properties and reactions. This principle provides the foundational knowledge for electron distribution in atomic orbitals, influencing chemical bonding and the periodic properties of the elements.