# Electrons In Atoms

### Page: 6, Ryleigh Purser

## Electron Configuration

The coordinates (“address”) for where electrons are

located within an atom;

includes the energy level, sublevel, orbital, and spin of

each electron

## Electron configurations for ions

Losing electrons = positive ions (Na+1)

Gaining electrons = negative ions (Cl-1)

Add or subtract the correct number of electrons from the

highest energy level

## RULES

__Electron Configurations are the way electrons are __

__arranged in various orbitals around the nuclei of atoms. __

**These rules tell us how to create orbital notation:**

__ Aufbau principle__ - electrons enter the lowest energy

first. This causes difficulties because of the overlap of orbitals of

different energies.

** Pauli Exclusion Principle** - at most 2 electrons per

orbital - different spins

- "No two electrons in an atom can have the same four quantum numbers."
- To show the different direction of spin, a pair in the same orbital

** Hund’s Rule **– Every orbital in a sublevel is singly occupied before any orbital

is doubly occupied.

- Also known as “the school bus rule”
- Electrons individually fill empty orbitals before pairing up

__ Heisenberg's Rule -__ “One cannot simultaneously determine both the position and momentum of an electron.”

- You can find out where the electron is, but not where it is going.
- You can find out where the electron is going, but not where it is!

All of the electrons in singly occupied orbitals have the same

spin (to maximize total spin).

## Orbital Notation

Orbital Notation is a drawing of the Electron Configuration using arrows. It is very useful in determining electron grouping and quantum numbers.

## QUANTUM NUMBERS

## PRINCIPLE QUANTUM NUMBER: N

- Principal quantum number
- Represents the main energy level of an electron
- Maximum # of e- in an energy level = 2n2

## ANGULAR QUANTUM NUMBER: L

- The 2nd quantum number
- Describes the orbital shape within an energy level
- Number of orbital shapes possible in energy level = n (same as principle quantum number)
- n = 1 has 1 shape, n = 2 has 2 shapes, etc...

## MAGNETIC QUANTUM NUMBER: M

- The 3rd quantum number
- Describes the orientation of the orbital in space (on x, y, or z axis)

## QUANTUM SPIN: S

- The 4th quantum number
- Describes the spin of electrons in orbitals
- Ground state: lowest energy arrangement of electrons
- spin up or spin down