The Quantum Mechanical Model

The Quantum Mechanical ModelThe nucleus is

found inside a blurry “electron cloud”

A area where there is a high probability of finding an electron.

Principal Quantum Number (n) = the energy level of the electron. (max # e- = 2n2 )

Sublevels- like theater seats arranged in sections (s,p,d,f) (# of sublevels = n )

Within each energy level, the complex math of Schrodinger’s equation describes several shapes.

These are called atomic orbitals - regions where there is a high probability of finding an electron

*No more than 2 electrons in each orbital*

Electron Configuration

Summary

s

p

d

f

# of orbitals

Max electrons

Starts at energy level

1 2 1

3 6 2

5 10 3

7 14 4

sublevel

Electron Configurations

Three main “guiding” principles:

The way electrons are arranged in atoms.

Aufbau principle- electrons enter the lowest energy first.

Electron ConfigurationsPauli Exclusion Principle- at most 2 electrons per orbital

Why only 2 electrons per orbital?like charges repel each other, but…

electrons spin on axis,

clockwise or counterclockwise,

creating magnetic polarization ( ↑↓ )

Hund’s Rule- When electrons occupy orbitals of equal energy (same sublevel ) they don’t pair up until they have to.

- one electron enters each orbital until all orbitals contain one electron with spins parallel.

Writing Electron Configurations(Letter - number designation)

H 1s1

Principle Energy Level

Sublevel

# of e-

Orbital Diagrams

Show each orbital as a circle, box, or line.

Show each electron as an arrow, ↑ or ↓ spin.

Label electron configuration (letter –number).

N 1s 2s 2p

7↑↑ ↑↑ ↑↓ ↓

2 2 3

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

Orbital (Aufbau) diagram

ExampleLet’s determine the electron configuration & orbital diagram for Phosphorus

Need to account for 15 electrons

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

1s22s22p6 3s23p3

Remember…When we write electron

configurations, we are writing the lowest energy (ground state) configuration.

Do Problems 21-24 pg 160

*** # 21 draw orbital diagrams,

not just e- configurations