Question

What are the different rules for filling up the orbitals? Explain each rule in detail.

Short answer

Question: List and briefly explain the three main rules that govern the filling up of orbitals with electrons in an atom. Answer: The three main rules for filling up orbitals with electrons are: 1. Aufbau Principle: Electrons fill orbitals of the lowest available energy level first before filling higher levels. 2. Pauli's Exclusion Principle: An orbital can hold a maximum of two electrons, and each electron in the same orbital must have opposite spins. 3. Hund's Rule: Electrons fill degenerate orbitals singly with parallel spins before occupying an individual orbital with opposite spins.

Step-by-step solution

Introduction to orbitals

Orbitals are regions around the nucleus in an atom where electrons are most likely to be found. Electron configuration is the arrangement of electrons in orbitals to determine the properties and reactivity of elements. The following rules are observed when filling up the orbitals with electrons.

1. Aufbau Principle

The Aufbau principle states that in the ground state of an atom, electrons fill orbitals of the lowest available energy levels before filling higher levels. This is similar to building a house from the ground up; thus, the name "Aufbau" comes from the German word for "building up." In other words, electrons will first occupy the lowest energy orbital, and then move to the next higher energy orbital once the lower ones are filled.

2. Pauli's Exclusion Principle

Pauli's exclusion principle explains that no two electrons in an atom can have the same set of four quantum numbers. In simpler terms, this means that an orbital can hold a maximum of two electrons, and each electron in the same orbital must have opposite spins. The spin is represented by an up or down arrow, and the fact that electrons in the same orbital have opposite spins ensures that their quantum numbers are unique.

3. Hund's Rule

Hund's rule states that when electrons occupy orbitals of equal energy, known as degenerate orbitals, they should first occupy these orbitals singly with parallel spins before occupying a single orbital with two electrons with opposite spins. This is because electrons are negatively charged particles, and having parallel spins minimizes repulsion between them, leading to a more stable and low-energy configuration. In summary, when filling up the orbitals, electrons follow these rules: 1. Fill orbitals of the lowest available energy level first (Aufbau Principle). 2. An orbital can hold a maximum of two electrons, and they must have opposite spins (Pauli's Exclusion Principle). 3. Electrons fill degenerate orbitals singly with parallel spins before occupying an individual orbital with opposite spins (Hund's Rule).