FACT:Chemical reactions

happen because electrons are shared or transferred from one substance to another

MAX NUMBER OF ELECTRONS IN AN ENERGY LEVEL

ENERGY LEVEL MAX # OF ELECTRONS

1 22 83 184 325 50

Write a mathematical equation that allows us to predict the Max # if we

know the energy level (n)

ENERGY LEVEL MAX # OF ELECTRONS

1 2

2 8

3 18

4 32

5 50

Max # = …n…

Equation to calculate Max # of e-

2n2

Where n is any energy level

There are 4 Quantum #s and those #s are

used to describe where an electron is likely to be found at any given

time

The first number we already know…

The Principle Quantum #

1st Quantum #Principle Quantum #

Specifies the energy level that the electron

is on

But this doesn’t explain why K’s last electron goes into the

4th energy level instead of the 3rd

2nd Quantum #

Specifies the shape of the sub-energy level

s and p Sub Energy Levels

III. Quantum Mechanical Model: Atomic OrbitalsE. Shapes of orbitals

d orbitals

ORBITALSpace occupied by a pair of electrons

Four Sub-Energy LevelsSub NRG

LevelShape Max # of

electrons# of

Orbitals

s Sphere 2 1

p Dumbbell 6 3

d 4-Lobed 10 5

f 6-8 Lobed 14 7

Sub-Energy Levels

So why do electrons fill in like they do?

i.e. why is K’s last electron in the 4th NRG level?

2 Factors Influencing Electron Placement

1.Energy Level- Closer to nucleus=easy

2. Subenergy level (shape) - spdf

Electron ConfigurationA detailed way of

showing the order in which electrons fill in around the nucleus

Electron Configuration Symbols

5f 3

Energy LevelSub-Energy

Level

# of e- in sub-energy

level

Electron Configuration PT

K

K: 2s21s2 4s13s22p6 3p6

Bohr Models

vs. e- Configs

Write the e- config for:

H:1s1

He: 1s2

Li: 1s22s1

K: 1s22s22p63s23p64s1

Again…Why are we concerned so much about electrons?

So do we really need to know

about all of the electrons?

Valence Electrons

Electrons in the outermost energy

level (involved in chemical reactions)

Noble Gas ShortcutK: 1s22s22p63s23p64s1

K: [Ar] 4s1

So what is different?

Aufbau Principle

All lower energy sublevels must be full before high energy sublevels begin

filling in

Steps for writing NGSC

1. Write the noble gas preceding the desired element [in brackets]

2. Carry on as usual

With only the first two Quantum #s, do we have as much information as possible as to where the electrons are likely to be

found?

3rd Quantum #m or magnetic Q#

Specifies the orientation of an orbital in space

4th Quantum #s or spin Q#

Spin of an electron on its own axis

Quantum Review1st Q#: Energy Level

2nd Q#: Shape of sub3rd Q#: Orientation of Orbital

4th Q#: Spin of e-

Quantum ReviewPrinciple (n): 1, 2, 3, 4, …

Azimuthal (l): 0, 1, 2, 3

Magnetic (ml): …-2, -1, 0, 1, 2

Spin (ms): +1/2 or -1/2

Pauli Exclusion Principle

No 2 electrons can have the same set of 4

quantum numbers

Arrow-Orbital Diagrams

A way to show orbital filling, spin,

relative energy

Hund’s RuleMost stable

arrangement of electrons is the one with the maximum number of

unpaired electrons

Arrow-Orbital DiagramsE

ner

gy

1s2s 2p

3p3s4s

3d

Lewis Electron Dot Diagrams

The easiest way to represent the # of valance electrons

Steps for writing electron dot diagrams

1. Write the element’s symbol

2. Write out e- config

3. Count # of valence e-s (1-8)

4. Place same # of dots as e- around symbol

Order to fill in an e- dot

Bm

12

34

5

6

7

8

What up?

Bm

12

Why do 1 and 2 fill in on the same side?

Who do 1 and 2 represent?

What up?

Bm

34

5

6

78

Who do 3-8 represent?

Why do 3,4,5 and 6,7,8 fill in on different sides?

What up?

Bm

34

5

6

78

Why will you never have

more than eight dots?

12

Examples of Lewis Electron Dots

What is different between the dot diagrams below and the

ones you’ve just seen?

The one you saw accounts for Quantum #s, this way doesn’t!

Flame Tests

Certain elements emit specific wavelengths of light when the electrons fall from outer energy levels back to their ground state.

The Electromagnetic Spectrum

Line Spectra of Excited Atoms• Excited atoms emit light of only certain wavelengths

• The wavelengths of emitted light depend on the element.

H

Hg

Ne