Final answer:
The three rules of orbital filling are the Aufbau Principle, Hund's Rule, and the Pauli Exclusion Principle, which dictate the order of electron placement within an atom's orbitals, and thus, its electron configuration and chemical properties.
Step-by-step explanation:
The student's question pertains to the three rules that govern how orbitals are filled with electrons in an atom. These rules include:
- Aufbau Principle: Electrons fill the lowest-energy orbitals first, starting with the 1s orbital and progressing to orbitals of higher energy levels.
- Hund's Rule: When electrons occupy orbitals of equal energy, known as degenerate orbitals, they fill each orbital singly before any orbital gets a second electron, with unpaired electrons having parallel spins.
- Pauli Exclusion Principle: No two electrons can have the same set of four quantum numbers, which means that an orbital can hold a maximum of two electrons with opposing spins.
These rules are based on principles of quantum mechanics and are essential for our understanding of atomic structure, specifically the electron configuration which is key to determining the chemical properties of an atom. The electron configurations are typically written with symbols signifying the principal quantum shell (n), the subshell type (s, p, d, f), and the number of electrons in each subshell. The way that electrons are arranged across the periodic table of elements can be explained in terms of the total energy, orbital angular momentum, and spin of electrons in an atom. Keeping these rules in mind, we understand the energetic stability of atoms and their tendencies in chemical bonding.