1. Periodic Trends Vocabulary: atomic radius metal electronegativity
“Wolfram”, Viza Arlington, 2010
Vocabulary:
atomic radius
metal
electronegativity
nonmetal
ionization energy
metalloid
shielding
malleable
ductile

2. Trend
What is a trend?
a pattern or direction
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3. Periodic trends Nonmetals Metaloids Metals
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.
Nonmetals
Metaloids
Metals

4. Important side-note dull good insulators brittle accept electrons
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

5. Important side-note
Metals
Nonmetals
sulfur
bromine
carbon

6. Important side-note
Metal
Nonmetal

7. 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

8. 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

9. 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.

10. 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.

11. 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.

12. 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
Atomic Radius values of group 1.
Atomic Radius values of period 4.
Option 2
Electronegativity values of group 1.
Electronegativity values of period 4.
Option 3
Ionization energy values of group 1.
Ionization energy values of period 4.

13. Questions
What trend do you see on each graph as you move across a period?
What trend do you see on each graph as you move down a family?

14. Atomic Radius Trends Decreasing Atomic Radius 
Increasing Atomic Radius 

15. Electronegativity Trends
Increasing Electronegativity
Decreasing Electronegativity

16. Ionization Energy Trends
Increasing Ionization Energy
Decreasing Ionization Energy

17. 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.

18. 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).

19. Why?
Now let’s look at some of the atoms in period 4.

20. 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.