Unit 1: Subatomic Organization and Spectroscopic Evidence

Quantum Mechanical Model

Describes electrons as energy states defined by wave functions rather than as particles in orbits.

Orbitals

Regions of space with a high probability (90%) of finding an electron.

Coulomb’s Law

Describes the electrostatic interaction between electrically charged particles.

Principal Quantum Number (n)

Indicates the main energy level or shell of an electron.

Angular Momentum Quantum Number (l)

Indicates the shape of the orbital, known as subshell.

Aufbau Principle

Electrons occupy the lowest energy orbitals first.

Pauli Exclusion Principle

No two electrons can have the same four quantum numbers; an orbital can hold a maximum of 2 electrons with opposite spins.

Hund’s Rule

Electrons fill degenerate orbitals singly with parallel spins before pairing.

Full Electron Configuration

Lists every subshell in order of increasing energy.

Noble Gas Notation

A shorthand to represent electron configurations using the last noble gas.

Cation

A positively charged ion formed by removing electrons.

Ionization Energy

The energy required to remove an electron from an atom.

Photoelectron Spectroscopy (PES)

An experimental technique that measures the binding energies of electrons to validate electron configurations.

Binding Energy (BE)

The energy required to remove an electron from an atom, calculated using the formula BE = hν - KE.

Kinetic Energy (KE) of ejected electron

The energy of an electron after being ejected from an atom by photon energy.

Energy Levels in PES graph

The x-axis represents binding energy, with higher energy corresponding to electrons closer to the nucleus.

Peak Height in PES graph

Indicates the number of electrons in a specific subshell.

Isoelectronic

Atoms or ions that have the same electron configuration.

Electrons in s-orbital

Can hold a maximum of 2 electrons.

Electrons in p-orbital

Can hold a maximum of 6 electrons.

Electrons in d-orbital

Can hold a maximum of 10 electrons.

Electrons in f-orbital

Can hold a maximum of 14 electrons.

Exceptions to Electron Configuration

Chromium and Copper have unique configurations for added stability in their d-orbitals.

Electron Configuration of Iron (Fe)

[Ar] 4s² 3d⁶.

Electron Configuration of Fe²⁺

[Ar] 3d⁶ (removal of 4s²).

Reading PES Spectrum

Analyze the position and height of peaks to identify electron subshells and ratios.