1. Periodic Trends

2. Group 1: The Alkali Metals
# of valence electrons: 1
Ion charge: 1+
Extremely reactive, only found in compounds.
React with water violently to produce H2 and a base.
Alkali metals:

3. Group 2: The Alkaline Earth Metals
# of valence electrons: 2
Ion charge: 2+
Very reactive, only found in compounds.
React with water quickly to produce H2 and a base.

4. Group 3-12: The Transition Metals
# of valence electrons: varies
Ion charge: 1+ to 7+
Range of reactivities
Some can be found pure in nature
Ions are brightly colored

5. Group 17: The Halogens # of valence electrons: 7 Ion charge: 1-
Extremely reactive & corrosive, only found in compounds
Only group with all three phases at room temperature

6. Group 18: The Noble Gases # of valence electrons: 8 Ion charge: 0
Completely Nonreactive

7. How are trends and properties related?
Different properties are caused by the attraction between the positive nucleus and the negative electrons.
Every atoms has the same number of protons as electrons.
The location of the electrons affects the properties of an atom.

8. Definitions to Know:
Valence electrons - outermost electrons that can be gained or lost in a chemical reaction
Shielding electrons - electrons in the energy levels between the valence electrons and the nucleus. They “shield” the valence electrons from the attraction of the nucleus.

9. Periods As we move across a period, the number of protons increase.
Across the period the number of electrons increase, but the number of shielding electrons stay the same.
Same number of shielding electrons but a larger number of protons = stronger attractive force from the protons.

10. Label each element in period 2
Number of protons:
Number of shielding electrons:
Number of valence electrons:

11. Groups
As we move down groups there is a trend in shielding electrons and valence electrons.
Each group has the same number of valence electrons.
Moving down the group, the number of shielding electrons increase.

12. Label each element in group 1
Number of shielding electrons:
Number of valence electrons:

13. Properties
The amount of shielding electrons and protons affect three important properties.
These properties help to predict how an element will react.

14. Atomic Radius The distance from the nucleus to the valence shell.
The size of the atom.

15. Electronegativity
The measure of the ability of an atom to attract electrons
How strong it pulls on other electrons.

16. Ionization Energy
The energy required to remove one electron from a neutral atom.
How much energy you need to knock off an electron.

17. Ions Atoms are always neutral.
The number of protons = number of electrons.
If an electron gains or loses an electron, it becomes an ion.

18. Why does an atom lose or gain electrons?
An element with a full outer shell becomes stable.
An atom will take or give up electrons to have a full outer shell.
A full outer shell = stability.

19. Types of ions There are two different types of ions.
Cation: A positive ion [ca+ion]
An atom that gives up electrons
Anion: a negative ion
An atom that gains electrons

20. Lithium The lithium atom has 3 electrons total.
The lithium ion has 2 electrons total and a positive charge of 1+.
One electron has been lost.
When an electron is lost, an atoms becomes a positive ion or a cation.