Download Electronegativity and Ionization Energy

Periodic Trends
Vocabulary:
1. metal
2. nonmetal
3. metalloid
4. malleable
5. ductile
“Wolfram”, Viza Arlington, 2010
6.
7.
8.
9.
atomic radius
electronegativity
ionization energy
shielding
Trend
• What is a trend?
▫ a pattern or direction
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Periodic trends
• The elements have trends, too. For example:
• Look at the zig-zag line on your periodic table.
Metals are on the left, nonmetals on the right,
and the metalloids are adjacent to the line.
Important side-note
Metals
• shiny
• good conductors of
electricity and heat
• hard
• malleable
• ductile
• give away electrons
Nonmetals
• dull
• good insulators
• brittle
• accept electrons
Metalloids
• some properties of
metals and some of
nonmetals
Important side-note
Metals
Nonmetals
sulfur
bromine
carbon
Important side-note
Metal
Nonmetal
Periodic Trends
• We’re going to look at trends on the
periodic table for physical properties of
elements. These are:
▫ atomic radius
▫ electronegativity
▫ ionization energy
Atomic Radius
• Distance from the nucleus of an atom to the
outermost electrons.
• Typically measured as half the distance
between the nuclei of identical bonded
atoms.
• The range is about 25 pm for the smallest
atoms to about 250 pm for the largest atoms
Electronegativity
• The ability of an atom in a chemical compound
to attract valence electrons. The scale is from 0-4
with 0 meaning no attraction for valence
electrons and 4 as the highest attraction.
Electronegativity
• What do you think would affect the ability of an
atom to attract electrons?
▫ Number of protons in the nucleus and distance of
electron from nucleus
• When an atom gains or loses
an electron, the atom is
called an ion.
This is a negative ion because it
gained an extra negative electron.
Ionization Energy
• The energy required to remove one electron
from a neutral atom of an element.
• What do you think
would affect the
amount of energy
required to remove
an electron?
▫ Number of protons
▫ Distance from nucleus
This is a positive ion because it
lost an electron.
Periodic Trends
• You will now look at trends on the periodic table for
atomic radius, electronegativity, or ionization energy.
• To do this, you will pick one of the following options and
use Open Office to make two graphs:
Option 1
1. Atomic Radius values of group 1.
2. Atomic Radius values of period 4.
Option 2
1.
2.
Electronegativity values of group 1.
Electronegativity values of period 4.
Option 3
1.
2.
Ionization energy values of group 1.
Ionization energy values of period 4.
Questions
1. What trend do you see on each graph as you
move across a period?
2. What trend do you see on each graph as you
move down a family?
Atomic Radius Trends
Decreasing Atomic Radius 
Increasing Atomic Radius 
Electronegativity Trends
Increasing Electronegativity
Decreasing Electronegativity
Ionization Energy Trends
Increasing Ionization Energy
Decreasing Ionization Energy
Why?
• Why do these trends exist? Let’s take a look first
at the elements in group 1 to find out about the
trends in families.
Group 1
Shielding: the blocking of the nuclear
charge to the valence electrons by the core
electrons. More energy levels = more
shielding. (Valence electrons are circled.)
Two consequences of more shielding:
1) Less attraction to outer electrons by
nucleus (lower electronegativity);
2) Easier to remove electrons from
valence shell (lower ionization energy).
Why?
Now let’s look at some of the atoms in period 4.
Period 4
K
Ca
Sc
Ti
V
Cr
•The number of protons increases as you go
across a period, yet the shielding does not
increase. More protons = more attraction of
the electrons to the nucleus.
•More attraction of electrons to nucleus =
higher electronegativity, higher ionization
energy, and smaller atomic radius.