1. The Periodic Table
Chapter 6

3. Steps to the Periodic Table
Chemists used the properties of elements to sort them into groups.
Triads (Dobereiner)
3 elements that were similar in properties and the lightest and heaviest averaged to the middle
Ex) Cl = Iodine = /2 equals Bromine 79.9
Periodic Table (Meyer and Mendeleev)
Sorted the elements based on atomic mass
The similar elements are organized into groups, which “flow” through periods

4. Periodic Law
When elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern
Must be sorted based on atomic number, not mass

5. 3 Classes of Elements Metals Non-Metals Metalloids % of elements ~80%
~15%
~6%
Luster
Shiny/bright
No/little luster
Medium
Bend or break?
Malleable and ductile (bendable)
Not malleable or ductile (brittle)
Brittle
State at room temperature (usually)
Solid
Gas
Density
HIGH
Low
Conductivity (electricity and heat)
High Conductivity
Low Conductivity (Insulator)
Semi-conductors
(Can be manipulated depending on conditions)

6. There is more than it seems…
The periodic table can tell you:
Element Symbol and Name
Classes of elements
Metal, non-metal, metalloid
Groups of elements
Electron configurations
Energy levels
Electrons in each
Atomic mass and number
State of matter (g, l, s)
And so much more!

7. Groups and Periods Groups (or families) form columns (vertical)
Have similar physical and chemical properties (reactivity, melting point, color, etc)
Periods form ROWS
The repetition of the groups with larger and larger sizes.
Also shows the energy levels described by Bohr, Heisenberg and Schrödinger

9. Groups of Elements
The columns in the periodic table are called “Groups” or “Families”
Elements in the same group have very similar physical and chemical properties (like family members)
There are 18 groups (ignoring the f-orbital metals, for some reason)
4 groups are important and very different from the other 14:
Alkali Metals – Group 1
Alkaline Earth Metals – Group 2
Halogens – Group 7
Noble Gasses – Group 8

10. WHY?!?
Elements in the same group have the same electron configurations!
Electron configuration determines how an atom reacts with other atoms.
Group 1
(Alkali metals) are s1
Group 2
(Alkaline earth metals) are s2
Group 7
(Halogens) are s2p5
Group 8
(Noble gasses) are s2p6

11. Periodic Trends
The elements in the Periodic Table can be used to predict properties like:
Atomic Size
What Ions are formed.
Ionization energy
Ionic size
Electronegativity

12. Atomic Size Two things determine how large an atom is:
Number of protons
More protons = smaller
Number of energy levels
More energy levels = larger
Atoms are larger in higher periods and smaller with higher groups
Ex) Francium is very large, Fluorine is very small.

14. Ions and Ionic Charge
Atoms become ions when they lose or gain electrons
Changes the charge from neutral to positive (when electrons are lost) or negative (when electrons are gained)
Cations (+)
I like cats, so cations are positive
Anions (-)
I don’t like onions, so they are negative
Cations are on the left, anions are on the right.

15. Ionization Energy How much energy it takes to take away an electron
Higher as you get closer to the noble gasses’ configuration.
Full (or empty) s and p orbitals
First ionization energy is higher at the top and the right side of the table
Ex) F is high, Fr is low

16. Ionic Size Cations (+) are smaller than their original atoms
Anions (-) are larger
Ex) C4+ is smaller than C4-
The same rules from atomic size (more energy levels = larger)

17. Electronegativity How much an atom is attracted to electrons
How much it “wants” an electron, or wants to give it away
Tells us how atoms treat their electrons
Electronegativity is highest at top right
Lowest at bottom left

19. WHY?!?!?
The atomic structure (protons, electrons, and energy levels) determine the periodic trends that exist.