Unit 7: Electrons
Test Date
1
Electromagnetic (EM) radiation
• A form of energy produced by electrical and
magnetic vibrations, or by the movement of
electrically charged particles
• Can travel in a “vacuum” (they do NOT need a
medium)
• Travel at the speed of light
2
Electromagnetic Spectrum
• Page 147 yellow book
Frequency and energy have a direct relationship. Watch this.
3
The Electromagnetic Spectrum
• Shows all types of EM radiation
• Red Martians Invaded Venus Using X-Ray Guns
• Shorter wavelength, high frequency light has higher
energy. Radio wave has the lowest energy.
– Gamma ray has the highest energy.
• High energy electromagnetic radiation damages
biological molecules. It is called ionizing radiation
Visible light
• Has wave-like and particle-like properties
• A particle of light is called a photon.
• Make the colors of the
rainbow
• ROY. G. BIV
• Each color has a
different wavelength,
energy, and frequency
5
Wave properties
• (f) Frequency-number of waves that pass a
given point per unit of time. (Hz)
• () Wavelength- distance between similar
points in a set of waves (crest to crest.) (m)
• 1m = 1.0 x 109 nm
6
Wave properties
• Amplitude- distance from crest or
trough to the normal (baseline).
Energy- Waves transmit energy.
The amount of energy
determines the amplitude and
the frequency.
7
Energy & Amplitude
• DIRECTLY related
• Determines the intensity of light
• The bulb on the right is emitting
energy with a higher amplitude
than the bulb on the left
8
Amplitude and Wavelength
Write this
9
Speed of the wave
Write everything
10
Practice Problem
• What is the wavelength of a radio wave with
a frequency of 1.01 x 108 Hz?
11
Energy of Electromagnetic Waves
Write everything
• The energy is carried in small packages called
photons. The energy carried in each photon is
calculated by:
E = hf
• E = energy
• h = Planck’s constant =h = 6.63 x 10-34 Js
• energy and frequency are DIRECTLY related
12
• Calculate the energy of a photon of radiation
with a frequency of 8.5 x 1014 Hz.
13
Electrons
Write everything
Electrons and Light
Vocabulary:
Ground State- the electron
occupies the LOWEST energy
level.
Excited State- the electron
temporarily occupies a
HIGHER energy level.
Energy is needed to go up a level
Photons are released when
falling down a level.
15
Quantum
• The specific amount
of energy absorbed
to excite an electron
Energy in
• The specific amount of
energy released when
an electron falls to the
ground state.
Energy out
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Atoms and Photons and Color
• Each atom’s electrons “jump” to certain excited
states.
• Each “fall” releases a photon of a certain
wavelength. These wavelengths of light correspond
to certain colors of light. The colors of light emitted
by an atom’s electrons can be used to identify the
element.
• The brightness of the color depends on the number
of photons emitted.
17
Auroras Explained
Why do auroras have different colors?
http://www.webexhibits.org
Electrons in an Atom
hyperphysics.phy-astr.gsu.edu
Where are the Electrons in the Cloud?
• Electrons are located at specific distances
from the nucleus
• The distance from the nucleus determines the
amount of energy associated with the
electrons
21
Principal Energy Levels
• 7 Energy Levels
• Abbreviated “n”
• n= 1 is closest to
nucleus and has
least energy
• n=7 is furthest
from nucleus and
has most energy
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Energy levels contain sublevels
•
•
•
•
•
There are four types of sublevels
s,
p,
d,
f
Energy Sublevels & the PT
Label your periodic tables according to the diagram
Bohr and Quantum Models
www.newbation.com
Electron sublevel (subshell) shapes
silver-bromide.tumblr.com
Three rules of electron configuration—
According to the aufbau
principle, electrons occupy the
orbitals of lowest energy first. In
the aufbau diagram, each box
represents an atomic orbital.
wavicles.webs.com
Three rules of electron configuration—
According to the Pauli exclusion principle, an
atomic orbital may contain at most two
electrons.
• A vertical arrow indicates an electron and its
direction of spin ( or ).
• An orbital containing paired electrons is written as
Three rules of electron configuration—
• According to Hund’s rule, electrons tend to
occupy all the sublevels (same energy orbitals)
singly before pairing up.
– Three electrons occupying a p orbital will be
arranged this way:
– Four electrons occupying a p orbital will have
paired electrons:
Examples of orbital diagram
Representing Electron Configuration
1s22s22p5
2
5
[He]2s 2p
Orbital Filling Diagrams
• Use arrows to
represent
electrons in
orbitals.
• The number of
arrows must
match the
number of
electrons
contained in the
atom
31
Electron Configuration
• Electron Configuration
is ordered the way you
read a book: from left
to right and top to
bottom
• Note that d orbital is 1
energy level behind
and the f orbital is 2
energy levels behind
the s & p orbitals
Practice
• 1. Write the electron configuration for the
following:
• Fe
• P
• Mg
• Ti
Ions
• Ions are atoms that have gained or lost
electrons; indicated by a superscript that
shows the ion’s charge
• Cl 1s22s22p63s23p5
• Cl-1 1s22s22p63s23p6 chlorine added an
electron
Chlorine adds a valence electron and becomes a
negative ion (anion)
.
• Sodium loses a valence electron and
becomes a pawsitive ion (cation).
Practice
• 1. Write the electron configuration for the
following:
• Na+1
• F-1
• Ba+2
• S-2
Review: Name the Element
• Given the Orbital Diagram
1s
2s
2p
• Write the Electron Configuration
2
2
4
1s 2s 2p
O
8e
Excited Electron Configuration
How is a carbon ground state electron
configuration different from a carbon excited
state electron configuration?
Ground State
1s
2s
1s2 2s2 2p2
Excited State
2p
1s
2s
1s2 2s1 2p3
2p
Electron Configuration
• Longhand Configuration
S 16e- 1s2 2s2 2p6 3s2 3p4
Inner Electrons
(Noble gas)
Outer (valence)
Electrons
• Shorthand Configuration
S
16e
2
4
[Ne] 3s 3p
Shorthand Electron Configuration
[Noble Gas Core] + Outer electrons
• Aluminum: 1s22s22p6 3s23p1
– shorthand configuration [Ne] 3s23p1
• Calcium: 1s22s22p63s23p6 4s2
– shorthand configuration [Ar] 4s2
The number of valence electrons is equal to the
number in the 1’s place of the group number.
Elements in the same group have the same # of
valence electrons.
41
Lewis-Dot Diagrams
• Lewis Dot Diagrams are a way to represent
the valence electrons in an atom.
– Element’s symbol represents the nucleus
and inner-level electrons
– Dots represent the valence electrons
– Dots are placed one at a time on the four
sides of the symbol, then paired until all
valence electrons are used…
– Maximum of 8 e- will be around the
symbol
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