Download Chapter 5 Electrons in Atoms

CHAPTER 5
“ELECTRONS IN ATOMS”
TERMS
1. Wavelength
8. Electron configuration
2. Frequency
9. Valence electron
3. Amplitude
4. Electromagnetic
spectrum
5. Atomic orbital
6. Excited state
7. Ground state
Take 15-20 minutes and
create a Vocabulary
Poster using a Chapter 3
Term
PARTS OF A WAVE
Crest
Wavelength
Amplitude
Origin
Trough
Wave
• Wavelength (represented by λ,
the Greek letter lambda) is the
shortest distance between
equivalent points on a continuous
wave.
Wave
• Frequency (represented by ν, the
Greek letter nu) is the number of
“waves” that pass a given point per
second.
• One hertz (Hz), the SI unit of
frequency, equals one wave per
second.
Wave
• In calculations, frequency is expressed
with units of “waves per second,”
example:
(
or (s–1).
• C = speed of wave = 3.00 x 108m/s
)
Calculating Wavelength of an EM Wave
• What is the wavelength of a microwave
having a frequency of 3.44 x 109 Hz?
1. Rearrange
Calculating Wavelength of an EM Wave
• Substitute c and the microwave’s frequency, v,
into the equation.
• Divide the values to determine wavelength,
λ, and cancel units as required.
ELECTROMAGNETIC SPECTRUM: EM
SPECTRUM
Used to describe electromagnetic radiation
Includes a wide range of wavelengths and frequencies.
Visible light are the colors we see
STOP
Do practice problems on white
boards.
Then, create your own EM Spectra.
Make interpretations of how an EM
Spectra reads to you.
Question 1
A helium-neon laser emits light with a
wavelength of 633 dm. What is the
frequency of this light?
Question 2
What is the wavelength of X rays having
a frequency of 4.80 x 1017 Hz?
Question 3
A laser emits light with a wavelength of
5.65x102 mm. What is the frequency of
this light?
Question 4
What is the wavelength of a ray that
has a frequency of 8.94 x 1016 Hz?
SECTION 5.2
Quantum Theory and The
Atom
Energy states
• The lowest energy state is called its
ground state.
• When an atom gains energy, it in an
excited state.
Quantum Numbers
• A quantum number, n, is
assigned to each orbit.
• For the first orbit n = 1, the
second orbit, n = 2; and so on.
BOHR SAID THAT:
• Energy related to orbit
• Electrons cannot exist between
orbits
• Higher energy level : Further away
from nucleus
• Maximum number of electrons in
outermost orbital the energy level
is stable (unreactive)
BOHR’S MODEL
Nucleus
Electron
Orbit
Energy Levels
CHANGING THE ENERGY
A hydrogen atom, with only one electron,
and in the first energy level. Ground state
Changing the energy
Heat, electricity, or light can move the electron
up to different energy levels. The electron is
now said to be “excited”
Changing the energy
As the electron falls back to the ground state, it
gives the energy back as light
LINE SPECTRUM OF VARIOUS ELEMENTS
STOP
Flame Test
Ground-state Electron
Configuration
The arrangement of electrons in an
atom is the electron configuration.
Low-energy systems are more stable.
Orbitals on the PT
In order of increasing energy, the
sequence of orbitals is
s, p, d, and f.
• S – 2 electrons
• P – 6 elections
• D – 10 electrons
• F – 14 electrons
WRITING ELECTRON CONFIGURATION
USE YOUR PT
1.Number row.
2.Orbital
3.Electrons = atomic
number
PRACTICE
How would you write the electron configuration
for Sodium?
What’s the atomic number?
11, so the superscript numbers should add
to 11
1s22s22p63s1
Do the superscript numbers should add to
11?
GROUND-STATE ELECTRON
CONFIGURATION
Three rules apply
•The aufbau principle/rule
•The Pauli exclusion principle/rule
•Hund’s rule
These all define how an electron is
arranged.
AUFBAU PRINCIPLE
States: each electron occupies the
lowest energy orbital available.
Step 1: determine ground-state by
learning the sequence of atomic
orbital's
•The aufbau Diagram
THE AUFBAU DIAGRAM
Each box represents an atomic
orbital.
Fig: 5.17 Page 135
ELECTRON CONFIGURATIONS…
2) Pauli Exclusion Principle - at
most 2 electrons per orbital different spins
ELECTRON CONFIGURATIONS
3) Hund’s Rule- When electrons
occupy orbitals of equal
energy, they don’t pair up
until they have to.
ELECTRON CONFIGURATIONS
Let’s write the electron configuration
diagram for Phosphorus

We need to account for all 15
electrons in phosphorus
Increasing energy
7s
6s
5s
7p
6p
5p
4p
4s
3p
3s
2p
2s
1s
6d
5d
4d
5f
4f
3d
The first two electrons go
into the 1s orbital
Notice the opposite
direction of the spins
only 13 more to go...
Increasing energy
7s
6s
5s
7p
6p
5p
4p
4s
6d
5d
4d
5f
4f
3d
3p
3s
2p
2s
1s
The next electrons go into
the 2s orbital
only 11 more...
Increasing energy
7s
6s
5s
7p
6p
5p
4p
4s
6d
5d
4d
5f
4f
3d
3p
3s
2p
2s
1s
• The next electrons
go into the 2p orbital
• only 5 more...
Increasing energy
7s
6s
5s
7p
6p
5p
4p
4s
6d
5d
4d
5f
4f
3d
3p
3s
2p
2s
1s
• The next electrons
go into the 3s orbital
• only 3 more...
Increasing energy
7s
6s
5s
7p
6p
5p
4p
4s
6d
5d
4d
5f
4f
3d
3p
3s
2p
2s
1s
• The last three electrons
go into the 3p orbitals.
• 3 unpaired electrons
NOBLE GAS NOTATION
Travel back to the last noble gas prior to
your element.
Sodium last pasted Ne therefore we can
write its electron configuration like…
 [Ne] 3s1
Reads: go to Neon then to the 3rd row in
the s orbital 1 element in.
VALENCE ELECTRONS
Define as the electrons in the atom’s outermost orbitals.
Example: Sulfur has 16 electron total.
Representative elements go by the
column number
Transition metals are given
Valance Electrons
1
2
3 4
5 6 7
8
ELECTRON-DOT STRUCTURE
Include:
 element’s symbol = innerelectrons
 Surrounded by dots = valence
electrons
Check out Table 5.5 as a
Reference
ELECTRON-DOT STRUCTURE
O
Cl
CLASSWORK
Create a poster of your element Include…
symbol
name
electron configuration
Aufbau diagram
electron-dot structure
Noble gas configuration if possible