1. 3.4 Periodic Table and Periodic Trends
Chemistry
Objectives 5:a-b, d-e

2. Essential Questions Why do we use the periodic table?
How did the periodic table come into being?
How is the periodic table arranged?
Why do groups share properties?
What are the different periodic trends and how do they change going across and down the periodic table?

3. Periodic Table Why do we have a periodic table?
The periodic table provides a way for organizing elements
Why does this matter?
The periodic table tells us what properties an element will have

4. History of the Periodic Table
The first periodic table was based off of the work of Mendeleev
Mendeleev arranged the elements in his periodic table in order of increasing atomic mass and grouped them according to properties.

5. History of the Periodic Table (cont)
The elements were grouped in columns
He even left places for undiscovered elements.
Look at Ar, Ca, and K what do you notice?

6. History of the Periodic Table (cont)
How is the current periodic table arranged?
Atomic number
Moseley arranged the periodic table by atomic number so that elements with the same properties fall into the same column

7. Arrangement of the Periodic Table
The vertical columns of the periodic table are called groups
The horizontal rows of the periodic table are called periods
The properties of the elements change as you move across a period from left to right.
The elements in the same group share properties

8. Group Properties
The common properties of elements in the same group come from having the same valence electrons
Valence electrons are “outer shell” or outer energy level electrons.
Valence electrons determine an element’s chemical properties

9. Periodic Trends: Radius
Atomic radius is the distance from the center of the nucleus to the outermost electron
Atomic radii decreases going across the periodic table and increases as you go down the periodic table

10. Periodic Trends: Radius (cont)
Increases because of adding e- shells
Decreases because of increased attractions between nucleus and e-
Changes going across rows are smaller than changes going down columns

11. Periodic Trends: IE
Ionization energy (IE) is the energy required to remove an e-
Ionization energy increases as you move from left to right across the periodic table and decreases as you go down the periodic table

12. Periodic Trends: IE (cont)
The IE increases going across because as radius decreases the attraction between the nucleus and the electrons increases
The IE decreases going down because the as radius increases the attraction between the electron and the nucleus decreases

13. Periodic Trends: IE (cont)
First ionization is lower in energy then the second
The second electron is harder to remove because it is closer to the nucleus
Valence electrons have a much lower IE then inner shell electrons because inner shell electrons are entire energy level closer to the nucleus

14. Periodic Trends: e- affinity
The energy change that occurs when an electron is acquired by a neutral atom is called the atom’s electron affinity.
Electron affinity generally increases across periods.
Smaller radius makes it easier to attract electrons
Electron affinity generally decreases down groups.
The larger radius makes it more difficult to attract/gain electrons
Exception is column 18

15. Periodic Trends: Electroneg
Electronegativity is a measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound.
Electronegativities tend to increase across periods, and decrease or remain about the same down a group.
Exception is column 18 equals 0

16. Essential Questions Why do we use the periodic table?
How did the periodic table come into being?
How is the periodic table arranged?
Why do groups share properties?
What are the different periodic trends and how do they change going across and down the periodic table?

17. 3.4 Tracked Assignment p 160 # 2-3, 5, 7 p 178 # 16, 18, 20, 22, 23