Quantum Mechanical Model AWESOME Quantum Mechanical Model February 28, 2007 Chem 102B

Probability of electron in 3-D space around the nucleus 1s Orbital ()

More “s” orbitals The higher the energy level, the larger the size, and the more nodes that are present Note the Nodes

Nodes Region of zero probablity

“P” Orbitals Dumbell shapes Sets of 3

The 3p orbital has 3 nodes

“D” Orbitals

“F” Orbitals

Quantum Numbers n - principal Size and Energy l - angular Shape integer values l - angular Shape integral values from 0 to n-1 ml - magnetic Orientation integral values from -l to l including 0 ms - spin Spin +1/2 or -1/2

Pauli Exclusion Principle Two electrons in the same orbital have opposing spins In a given atom: No two electrons can have same QN’s!

Aufbau Principle “Building up” Add electrons one at a time Energy tells us what order to fill the electrons in the orbitals - Hund’s Rule Lowest energy equals max number of “unpaired electrons”

Periodic Table

Ionization Energies Energy required to completely remove an electron from an atom.

Electron Affinity The energy change associated with the addition of an electron to a gaseous atom X(g) + e-  X-(g) Atoms that tend to form negative ions release more energy when an electron is added

Atomic radius Half the distance between the nuclei in a molecule consisting of identical atoms Not exact measure!

Radii trends Down the group the atoms get larger, more electrons, bigger size. Across the period the atoms get smaller, why?

Summary of Trends Too erratic to predict IE EA R