Chemistry

Chapter 5

Notes #3

Rules

Neils BohrAdded on to Planck’s and Einstein’s theories

• Lowest available energy state of an atom

• Ground State

• When an atom gains energy =

• Excited StateThis applies to the Atomic emission spectra!!

Rules

Heisenberg Uncertainty PrincipleIt is fundamentally impossible to know

precisely both the velocity and the position of a particle at the same time

Ex. Blades of a running fan (on high)That is how the electrons are traveling

Rules

Aufbau PrincipleElectrons “fill”

atoms starting at the lowest energy and moving out to higher amounts of energy

Excited vs. Ground State

Rules

Pauli Exclusion PrincipleA max of 2 electrons

will occupy a single orbital

The electrons have opposite spins

The opposite spin requirement is born out of quantum physics….2 electrons cannot have the same quantum number – therefore they must have opposite spins

Rules

Hund’s Rule Single electrons with

the same spin occupy each orbital (of a multi-orbital sublevel) before additional electrons with opposite spins occupy the same orbital.

Remember – Electrons are all negative – so they repel each other –meaning they take as much space as they can…

“Blocks on the table!

Noble gas Configuration

Shorthand to electron configuration Steps:

Find the noble gas that comes directly before the element you are looking at

Put the chemical symbol of the noble gas in brackets

Then, continue the electron configuration at the beginning of the row immediately following the noble gas

Noble gas Configuration

Element Atomic #

e- conf Noble gas Conf.

Na 11

Ca 20

Sr 38

P 15

Br 35

I 53