Chapter 5 Notes
Chem210FL
page 1
Dr. Lara Baxley
Chapter 5 Notes: Electronic Structure and Periodic Trends
I. Electromagnetic Radiation
Learning Goal: Compare the wavelength of radiation with its frequency
A. Wavelength and Frequency
Wavelength (λ
λ):
Frequency (v):
Speed of light (c):
Mathematical relationship between these:
Important Concepts:
URL for animation: http://www.micro.magnet.fsu.edu/primer/java/electromagnetic/index.html
Practice
Calculate the frequency, in Hz, of red light with a wavelength of 695 nm.
Chapter 5 Notes
Chem210FL
page 2
Dr. Lara Baxley
B. Electromagnetic Spectrum
II. Atomic Spectra and Energy Levels
Learning Goal Explain how atomic spectra correlate with the energy levels of atoms
A. Photons
Photon:
B. Atomic Spectra
An interesting phenomenon: Different colors are produced when electricity is
passed through a noble gas or when different elements are put in a flame
URL for animation: http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/pem1s3_1.swf
Atomic spectra:
Chapter 5 Notes
Chem210FL
page 3
Dr. Lara Baxley
C. Electron Energy Levels
Electron Energy Levels:
Principal Quantum Numbers (n):
Ground State:
Ground state
Excited state:
D. Changes in Energy Levels
When an element is put in a flame or electricity,
_____________________________________________
When the electrons drop back to the lowest level,
________________________________________
The bigger the change in energy levels,
_____________________________________________
Learning Check
A. Is energy absorbed or emitted when an electron moves from the first energy level
(n =1) to the third energy level (n = 3)?
B. Is energy absorbed or emitted when an electron falls from the third energy level to
the second energy level.
C. If one electron moves from n = 3 to n =1, and another electron moves from n = 4 to
n =1, which electron releases the most energy?
Chapter 5 Notes
Chem210FL
page 4
Dr. Lara Baxley
III. Sublevels and Orbitals
Learning Goal Describe the sublevels and orbitals in an atom
A. Sublevels
• Each energy level has sublevels
• Each sublevel has a different shape of where the electrons can exist
• Each sublevel is identified by a different letter, s, p, d, or f
• Not all sublevels are present in each level (see diagram)
B. Orbitals
An orbital
• is a three-dimensional space around a nucleus where an electron has the
highest probability of being found
• has a shape that represents its electron density (not a path the electron
follows)
s, p, d, and f sublevels have differently shaped orbitals
s Orbitals: s orbitals are in the s sublevel
Chapter 5 Notes
Chem210FL
page 5
Dr. Lara Baxley
p Orbitals: p orbitals are in p sublevel
Sublevels in Energy Level 2
C. Orbital Capacity and Electron Spin
Each orbital can hold up to _______ electrons
The electrons in an orbital have opposite ____________
The opposite spins on electrons are represented as _____________________
Representation of an orbital with two electrons:
IV. Orbital Diagrams and Electron Configurations
Learning Goal Draw the orbital diagram and write the electrons configuration for an
element
A. Order of Orbital Filling
•
Orbitals fill with electrons
from ___________________________
to _____________________________
Chapter 5 Notes
Chem210FL
page 6
Dr. Lara Baxley
B. Orbital Diagrams
An orbital diagram is a drawing that represents the level and sublevel locations
of the electrons in an atom of a given element.
C. Electron Configurations
An electron configuration is a shorthand notation of an orbital diagram.
Orbital Diagrams and Electron Configurations of the First 10 Elements:
V. Using the Periodic Table to Determine Electron Configuration
Learning Goal Write the electrons configuration for an atoms using the periodic table
A. Determining Electron Configurations
Chapter 5 Notes
Chem210FL
page 7
Dr. Lara Baxley
Examples
1. Use the periodic table to determine the electron configurations of the following
elements
a. Oxygen
b. Nickel
2. Draw orbital diagrams for the
elements listed above
a. Oxygen
b. Nickel
B. Abbreviated Electron Configurations
In an abbreviated electron configuration, the configuration of the previous noble gas
is replaced by writing its symbol
Example
Write the abbreviated electron configuration of Nickel.
Practice
1. Write the abbreviated electron configurations of each of the following elements.
a. Sulfur
b. Iodine
2. Draw the abbreviated orbital diagram for iodine.
Chapter 5 Notes
Chem210FL
page 8
Dr. Lara Baxley
C. Two Notable Exceptions to Predicted Electron Configurations
(there are many other exceptions, but you only need to know these two!)
Cr:
Cu:
VI. Periodic Trends of the Elements
Learning Goal Use the periodic table to predict relative properties of elements
A. Group Number and Valence Electrons
Valence Electrons: __________________________________________
For main group elements (A groups), the number of valence electrons is
_______________________________________________________
In electron-dot symbols, valence electrons are represented as _______
Practice Electron-Dot Symbols
1. Draw the electron dot symbols for the following elements.
a. Calcium
c. Argon
b. Phosphorus
B. Atomic Radius (i.e. atomic size)
The atomic radius (atomic size) is determined by _______________________
•
across a period, same energy level, more electrons, also more protons,
attractive force strong, pulls in electrons
→ across a period atomic size ______________________
•
down a group, higher energy levels, atomic size increases with higher
energy levels
↓ down a group, atomic size ______________________
Chapter 5 Notes
Chem210FL
page 9
Dr. Lara Baxley
C. Ionization Energy
Ionization energy is the energy it takes to ___________________________
The smaller the atomic radius (i.e. the closest the outer electrons are to the
nucleus, the _____________________ the ionization energy.
→ across a period ionization energy, ______________________
↓ down a group ionization energy, ______________________
Practice Periodic Trends
1. Which atom in each pair is larger?
a. Ca or Sr
b. P or Cl
c. K or Kr
2. Which has the higher ionization energy, N or P?
3. For which atom would it be easiest to remove an electron, Mg or Na?
Suggested textbook problems:
Ch5: 3,5,7,17,19,23,*25,*27,31,33,35,37,39,41,43,45,47,49,51,53,57,59,61,63,65,
67,73,75,77,79,81,83,85,89,91,93,95,97,99,101,105,107,*109,117