Periodic Trends

1
Periodic Trends
You will know what ionization energy is and how
it trends on the periodic table
You will know what electron affinity and
electronegativity are and how they trend on the
periodic table
You will know how cations and anions compare in
size to their parent atoms
2
What Are Ions?
Ion Definition - An atom or group of bonded
atoms that have a positive or negative charge
Na
Sodium cation
Cl-
Chloride anion
NH4
Ammonium cation
SO32-
Sulfite anion
Any process that creates an ion is referred to as
ionization.
3
Ionization Energy
The energy required to remove one electron from a
neutral atom ionization energy
A energy ------gt A e-
For main group elements .
Ionization energy increases across each period
Ionization energy decreases down each group
4
(No Transcript)
5
What determines IE?

• The greater the nuclear charge, the greater IE
  (for periods)
• Greater distance from nucleus decreases IE (for
  groups)

6
Electron Affinity
The energy produced when an electron is added to
neutral atom electron affinity
A e- ------gt A- energy
7
Electron Affinity Trend
Electron Affinity The energy release when an
electron is added to an atom. Most favorable
toward NE corner of PT since these atoms have a
great affinity for e-.
8
Electronegativity
Measure of how much an atom can attract electrons
Higher electronegativity results in higher number
Highest value is 4.0 - Fluorine Lowest value is
0.7 - Francium
Proposed by Linus Pauling --- Useful in
describing properties of compounds
9
Electronegativity Chart
10
Trends in Ionic Size(page 175-176 book)
Cations are always smaller than the atoms they
come from. Example Na is smaller than Na
Anions are always larger than the atoms they come
from. Example F- is larger than F
11
Ionic Radii vs Atomic Radii
12
A Closer Look At Ions
13
Putting it all Together
14
Group Properties of Some Main Group Elements
Alkali metals
Alkaline Earth Metals
Halogens
Halogens 2
Noble Gases
Braniac Alkali Metals