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THE ELECTRON
CHAPTER 5
Chapter 5 Overview
Chapter 5 focuses on the electrons within
atoms for two reasons:
1. Electrons account for the element’s
reactivity or “personality”
2. Electrons are the first things that
surrounding atoms encounter when they
come upon the atom
5.1 Light & Quantized Energy
•Electromagnetic Radiation
-A form of energy that exhibits wavelike behavior as it
travels through space.
-Visible light
-Microwave
-X-rays
-Radio waves
-Television waves
•All electromagnetic waves are standing waves that have frequency,
wavelength, and amplitude
Waves
•λ (wavelength)
-the distance between crests or troughs
•V (frequency)
-the number of waves that pass a point every second measured in
Hertz
(Hz)
•A (amplitude)
-The highest point or the lowest point from the equilibrium line of a
wave
•C (speed of a wave)
-The speed = wavelength x frequency
•T (period of the wave)
-complete cycle of the wave crest-trough-crest
•Speed of Electromagnetic Magnetic Radiation
-3.00 x 108 m/s
Wavelength vs. Frequency
• Wavelength and
frequency have an
inverse relationship
Electromagnetic Spectrum
Planck’s Theory
•There is a specific amount of energy that matter can gain or lose.
This small amount of energy is a quanta.
•Quantum-is the minimum amount of energy that can be gained or
lost by an atom.
•Quantum-fixed amount
• Mathematical formula for quantum energy (E= v x h)
E= energy
v= frequency
h= Planck’s constant (6.626 x 10-34 J per second)
Einstein & Planck
•Einstein used photons to explain the photoelectric
effect.
•Einstein proposed that the energy of a photon of light
must have a certain minimum value to cause the
ejection of a photoelectron.
Emission & Line Spectra
• Atomic Emission Spectrum/Line Spectrum
– contains only certain colors, or wavelengths
• All elements emit light when they are vaporized
in an intense flame or when electricity passes
through their gaseous state.
• Atoms absorb then release energy in the form of
light.
• Every element emits light containing only certain
wavelengths (line spectrum, color)
5.2 Quantum Theory and the Atom
• Neils Bohr Atomic Model
– Described the atom as
electrons moving around
the nucleus in well
defined orbits .
• The smaller the orbit, the
lower the energy.
• The larger the orbit, the
higher the energy.
-n=1, n=2, n=3, n=4
• Ground State
– the lowest allowable
energy state of an atom
Excited Electrons
• When electrons in the ground
state gain energy, they can
move a greater distance from
the nucleus to an excited
state.
• When the electrons lose the
gained energy they fall back
to the ground state and
release the energy in the form
of radiation.
http://micro.magnet.fsu.edu/primer/java/fluorescence/exciteemit/
Electron Excitation
• Electrons are not stuck in ONE principle energy level
– If energy is added to the atom, the electrons can jump
to higher energy levels
• Ground State
– Resting state
• Excited State
– State where electron goes when energy is
added
– Atomic Spectrum (energy released)
• Wavelength
• Frequency
• ROYGBIV
Broglie & Heinsberg
• Louis de Broglie
– predicted all moving particles have wave
characteristics.
• Heisenberg Uncertainty Principle
– it is impossible to know precisely the
velocity and position of a particle at same
time.
Schrödinger
• Quantum Mechanical
Model of the Atom
-An atomic model in
which the electrons
are treated as waves.
• Atomic Orbital
-a three dimensional
region around the
nucleus
Principle Energy Levels
•Energy levels of an atom
-n specifies the atom’s major energy levels
-The principal energy levels are assigned a
number from 1-7
-The principal energy levels contain energy
sublevels
-These sublevels are called orbitals.
n=1
-principal energy level =1
-consists of 1 sublevel
n=2
-principal energy level =2
-consists of 2 sublevels
n=3
-principal energy level =3
-consists of 3 sublevels
n=4
-principal energy level =4
-consists of 4 sublevels
Atomic Orbitals
•The orbital is a particular volume of space around the
nucleus.
•Each atomic orbital is a three dimensional region around
the nucleus.
•Each orbital describes the electron’s probable location.
-All Electrons occupy energy levels only… no electrons between
-All principal quantum numbers n = 1, 2, 3, 4
-All Communicates the distance from the nucleus and amount of
energy
-All Outermost electrons communicate the row on the periodic table
Principle Energy Levels
•Principal Energy Levels
( n = 1 through 7 )
•Sublevels
-( s. p. d. f )
•Orbitals
-s = 2 electrons
-p = 6 electrons
-d = 10 electrons
-f = 14 electrons
5.3 Electron Configuration
•The arrangement of electrons in an atom.
-s =1 orbital
(maximum of 2 electrons )
-p = 3 orbitals
(maximum of 6 electrons)
-d = 5 orbitals
(maximum of 10 electrons)
-f = 7 orbitals
(maximum of 14 electrons)
Maximum Electrons
• Each energy level can
only hold so many
electrons
– Energy Level 1 (n=1)
• MAXIMUM of 2 e-
– Energy Level 2 (n=2)
• MAXIMUM of 8 e-
– Energy Level 3 (n=3)
• MAXIMUM of 18 e-
Stop Notes Part 1 Here
• Complete Sections 5.1-5.2 Review
Worksheets
Electron Configuration using the
Periodic Table
Electron Arrangement
• Called ELECTRON
CONFIGURATION
–A series of letters & numbers
giving specific information about
every electron in an atom
–We will use the analogy of CHIEF
HOTEL to describe Electron
Configuration set-up and rules….
CHIEF HOTEL
ACCOMODATIONS
• Single Room (s)
– One “bed”
– Two “guests” maximum
– Spruce (green) in color
– Located on floors 1-7
CHIEF HOTEL
ACCOMODATIONS
• Prestige Room (p)
– Three “beds”
– Six “guests” maximum
– Purple in color
– Located on floors 2-7
CHIEF HOTEL
ACCOMODATIONS
• Deluxe Room (d)
– Five “beds”
– Ten “guests” maximum
– Dandelion (yellow) in color
– Located on floors 3-6
CHIEF HOTEL
ACCOMODATIONS
• Fabulous Room (f)
–
–
–
–
Seven “beds”
Fourteen “guests” maximum
Fuchsia in color
Located on floors 4 & 5
Electron Configuration Practice
Complete the electron configurations for the
following elements:
12
Mg
1s2 2s2 2p6 3s2
24.02
36
Kr
83.80
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
Orbital Diagrams
•Aufbau principle
-each electron occupies the lowest energy orbital
available.
•Pauli exclusion principle
-maximum of two electrons may occupy a single
orbital
•Hund’s rule
-single electrons with the same spin must occupy
equal energy orbital before an additional electron
of an opposite spin can occupy the same orbitals.
Orbital Diagrams
Mg
___
1s
___ ___ ___ ___
2s
2p
___
3s
Orbital Diagrams
Noble Gas Notation for Electron Configuration
Example:
Bohr Model – Sodium (Na)
Atomic Number
11
Protons
11
Neutrons
12
Electrons
11
Valence Electrons
• Electrons in the atom’s outermost
orbitals
– Orbitals are associated with the atom’s
highest principal energy level
– These electrons will be the ones
involved in reactions
– Use the valence electrons to complete
the electron dot structure.
Na = 1s22s22p63s1
Sodium has ONE valence electrons
Group
Name
Valence e-
1A
Alkali
1
2A
Alkaline Earth Metals
2
3A
Boron Group
3
4A
Carbon Group
4
5A
Nitrogen Group
5
6A
Oxygen Group
6
7A
Halogen
7
8A
Noble Gases
8
Electron Dot Structure
• Elements symbol represents the atomic
nucleus and inner electrons Na
• Symbol is surrounded by dots representing
the valence electrons.
Na
• Apply one dot per side and then pair up…
Li
O
Ne
Mg