1 / 35

Chapter 5 - PowerPoint PPT Presentation

Chapter 5. Electrons in Atoms. Wave Nature of Light. Wavelength ( λ ) – shortest distance between equivalent points on a continuous wave (unit: m or nm) Ex: Crest to Crest or Trough to Trough. Wave Nature of Light.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

PowerPoint Slideshow about ' Chapter 5' - wilson

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Chapter 5

Electrons in Atoms

• Wavelength (λ) – shortest distance between equivalent points on a continuous wave (unit: m or nm)

• Ex: Crest to Crest or Trough to Trough

• Frequency (ν) – the number of waves that pass a given point per second (unit: Hz or 1/s)

• 1 Hertz (Hz) = 1 wave per second

• form of energy with wave-like behavior

Wavelength and Frequency Relationship:

Inverse Relationship: Long Wavelength mean Low Frequency

• ALL electromagnetic radiation moves at the speed of light

• speed of light = c = 3.0 x 108 m/s

• Formula:

c = λν = (wavelength) x (frequency)

• Microwaves are used to cook food and transmit information. What is the wavelength of a microwave that has a frequency of 3.44x109 Hz?

Given:

ν = 3.44 x 109 Hz

Find: λ = ?

Equation:

• shows all forms of electromagnetic radiation (pg 139)

• shows all forms of electromagnetic radiation (pg 139)

• Ground State: lowest, most stable energy state of an electron

• Excited State: has more energy than the ground state

• Photon: particle of electromagnetic radiation

• Light is both a particle and a wave

• Every element has its own specific atomic emission spectrum

• When an excited electron returns to the ground state, it gives off a photon of electromagnetic radiation.

• Electrons are located in the electron cloud.

• The electron does not have a definitepath nor can it be specifically located, but we can predict its whereabouts based on probabilities called orbitals

Quantum Theory and Numbers

• gives an electron’s position in an atom

• 4 quantum numbers

• n

• l

• m

• s

Quantum Numbers

Indicates the average distance of the electron from the nucleus

n is the period number (a number between 1 and 7)

n

Principle QN

state

Subshell indicates the shape of the orbital

Shapes are labeled by letters (s,p,d,f)

l

Orbital QN

city

Indicates the orientation in space (dependent on the shape)

s = 1 orientation

p = 3 orientations

d = 5 orientations

f = 7 orientations

m

Magnetic QN

street

Indicates the direction of spin of the electron

Spin is either +1/2 or -1/2

s

Spin QN

Side of street

Important note:

EVERY electron in an atom has a specific, unique set of the four quantum numbers!

• Discovered and presented by Niels Bohr in the Bohr model of the atom

• Indicates:

• The distance from the nucleus

• The size/volume of the electron’s orbital

• The atom’s major energy levels

• The further the electron is from the nucleus the greater n will be

• The larger the n the greater volume of the electron cloud and the greater the energy

n can be a number between 1 and 7

• Indicates the shape of the orbital (the sub shell)

p

f

d

s

The shape is determined by l but m determines how the shape is oriented in space.

s orbital – spherical

Only 1 orientation

The shape is determined by l but m determines how the shape is oriented in space.

p orbital: “dumbbell”

3 orientations

The shape is determined by l but m determines how the shape is oriented in space.

d orbital:

5 orientations

The shape is determined by l but m determines how the shape is oriented in space.

f orbital:

7 orientations

Each orbital orientation can hold only 2 electrons:

s : 1 orientation = 2 total electrons

p : 3 orientations = 6 total electrons

d : 5 orientations = 10 total electrons

f : 7 orientations = 14 total electrons

• Indicates which direction the electron spins

• The 2 electrons in an orbital orientation will have opposite spins ( + ½ or – ½)

Pauli Exclusion Principle

Each electron in an atom has a unique set of quantum numbertherefore, a maximum of two electrons can occupy a single atomic orbital

• Quantum numbers are used to write electron configurations of an element

Hydrogen H

Atomic number: 1

1s1

n

# of electrons

Shape determined by l

Aufbau Principle

Each electron occupies the lowestenergy orbital available

Method 1

Write the configuration of Na:

1s2

2s2

2p6

3s1

Na has 11 electrons

The electrons from the configuration should add up to 11.

Remember: s can hold 2 electrons, p 6, d 10 and f 14

Use the periodic table

Always start at 1s

Ar

Argon’s atomic number is 18

The superscripts from the electron configuration added equal 18.

Write the electron configuration for Ar:

1s2

2s2

2p6

3s2

3p6

• Write the electron configuration for the following elements:

C:

P:

Ag:

Rn:

1s22s22p2

1s22s22p63s23p3

1s22s22p63s23p64s23d104p65s24d9

1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p6

• Electron configurations can be written as diagrams

• Orbital Notation diagrams show the individual orientations and the electrons that fill them.

• Hund’s Rule: fill orbitals so that the number of unpaired spins is maximized; electrons will fill orbitals before pairing up

• Write the orbital notation for Carbon:

Electron configuration: 1s22s22p2

1. Write a line for each orientation associated with a orbital shape: s = 1, p = 3, d = 5, f = 7

2. Fill electrons in each shape. Place a single electron in each orbital before pairing them up.

1s

2s

2p

• Write the orbital notation for the following elements:

C:

P:

Ag:

Rn:

All electron configurations can be abbreviated…

Electron Configuration for Ca is:

Noble gas configuration for Ca is:

• The outer electrons are use to draw Lewis Dot Diagrams

• The number of electrons in the highest principle quantum number (largest “n” values) determines the number of electrons in the diagram

H

.

.

Be

:

.

.

N

.

:

:

Ne

:

:

Examples

H 1s1

Be 1s22s2

N 1s22s22p3

Ne 1s22s22p6

1 electron

2 electrons

5 electrons

8 electrons