Sections 7.1 – 7.3 Electron Spin, Orbital Energies and Electron Configurations

Atomic Electronic Structure In these sections… Electron Spin and Magnetism Energies of Orbitals Electron Configurations of Atoms

Electron Spin: Electrons exhibit a magnetic field We think of them as spinning. They can spin only two ways: think of it as left or right Spin quantum number: ms can be +1/2 or -1/2

Magnetic Properties come from additive effects of electron spins Magnetic Properties come from additive effects of electron spins. Diamagnetic: all electrons are paired Paramagnetic: 1 or more unpaired electrons Ferromagnetic (real magnets): unpaired electrons all lined up in the same direction

Pauli Exclusion Principle No two electrons in an atom can have the same 4 quantum numbers n, ℓ, mℓ define an orbital Therefore: an orbital can hold only two electrons, with opposite spins because ms can only be +1/2 or -1/2

Pauli Exclusion Principle What’s allowed?

Orbital Energies Single Electron Atoms Multi-electron Atoms Why? With a single electron, energy depends only on how far from the nucleus. With multiple electrons, e-e- repulsions also play a role and differ depending on orbital shape.

Single Electron Atoms Multi-electron Atoms For most atoms: Energy increases as n increases: 1 < 2 < 3 < 4 … Energy increases as subshells progress: s < p < d < f

Atomic Electron Configurations An atom has lots of electrons and lots of orbitals. Which orbitals do the electrons occupy?

Atomic Electron Configurations An atom has lots of electrons and lots of orbitals. Which orbitals do the electrons occupy? Electrons fill the lowest energy orbitals first. Electron Configuration: a listing of how many electrons occupy each orbital.

Electron Configurations General Rule: electrons fill lowest energy orbitals first Sodium, Na as an example Na has 11 electrons. Fill 2 electrons per orbital till you run out A box represents an orbital. An arrow represents an electron.

Electron Configurations: Three Notation Types 1. 2. spdf (or spectroscopic) notation: List subshells and how many electrons they contain: 1s22s22p63s1 3. Noble gas notation: short [Ne]3s1 Where [Ne] = 1s22s22p6

Electron Configurations and the Periodic Table Examples using Electron Configuration Simulation Periodic Blocks Hund’s Rule (using the p block) n value increases as you move down table Anomalies: Cr and Cu

Electron Configurations and the Periodic Table: Periodic Blocks

Electron Configurations and the Periodic Table II

Periodic Table and the Order of Filling In what order are subshells filled?

Hund’s Rule: Subshells are filled to give the maximum number of unpaired electrons

Using Periodic Blocks: C

Using Periodic Blocks: Cl

Noble Gas Notation: Mg

Noble Gas Notation: Mg

Diamagnetic vs. Paramagnetic Elements

d-Block Elements: Fe

Two Anomalies: Cr and Cu