1. Periodic Trends

2. The Periodic Table Rows = periods (left to right)
Columns: families or groups(up & down)
Alkali Metals (Group 1 or IA)
Alkaline Earth Metals (Group 2 or IIA)
Halogens (Group 17 or VIIA)
Noble Gases (Group 18 or VIIIA)
A-group families = main group or representative elements
B -group = transition elements or metals

3. The periodic table

4. Metals, Nonmetals, and Semiconductors
What makes an element a metal?
A substance that has a tendency to lose electrons to empty its valence shell.
What makes an element a nonmetal?
A substance that has a tendency to gain electrons to fill its valence shell.
A few elements exhibit properties of both metals and nonmetals.
These elements are called metalloids or semiconductors

5. Metals, nonmetals and semiconductors

6. Metals, nonmetals and semiconductors
Noble gases - filled shells, stable elements
1A, 2A, & 3A Groups
Lose outer electrons to become positive ions - cations
All elements in these groups are metals
5A, 6A & 7A Groups
Tend gain electrons and form negative ions - anions
All elements in these groups are nonmetals
Semiconductors- intermediate between metals and nonmetals

7. Oxidation Numbers of Ions Formed
Oxidation number refers to the charge on the ion formed from atoms in a particular group

9. Atomic Radius
Remember, electrons are added one at a time moving from left to right across a period
As this happens, the electrons of the outermost shell experience increasingly strong nuclear attraction
Electrons become closer to the nucleus

10. Atomic Radius
The increased number of protons going across a given period increase the pull on the outer shell electrons
Shrinking atom
Going down a group, each new element represents a new shell of electrons and thus a fatter element!
Generally, the atomic radius decreases across a period from left to right and increases down a given group

11. Relative Atomic Radii

12. Ionization Energy
Ionization energy- energy required to completely remove an electron from a gaseous atom
The closer an electron is to the nucleus, the more difficult it will be to remove
Greater ionization energy

13. Ionization Energy
Ionization energies increase moving from left to right across a period (decreasing atomic radius) and decrease moving down a group (increasing atomic radius)

14. Ionization Energy

15. Ionization Energy
Metals have lower ionization energies than non-metals that share their period or group.
The lower the ionization energy for metals, the more reactive they will be.
Non-metals have higher ionization energies than metals that share their period or group.
The valence shell is closer to the nucleus, thus electrons experience a stronger nuclear force of attraction.

16. Electronegativity
Electronegativity is a measure of the attraction of an atom for the electrons in a chemical bond
AKA- electron affinity
The higher the electronegativity of an atom, the greater its attraction for bonding electrons
The atom wants to bring in electrons
Electronegativity increases from left to right across a period and decreases as you move down a group

17. Electronegativities of the representative elements

18. Electronegativity
The smaller the atom the easier it is to attract electron and the more reactive a non-metal will be.
High electronegativity
Atoms with low ionization energies have low electronegativities because their nuclei do not exert a strong attractive force on electrons

19. Summary

20. Ionic Radius- Cations
Cations are formed when an atom gives up an electron
Positive ion
All metals form cations
Down a group, the ionic radius of cations increases
Extra shells of electrons

21. Ionic Radius- Cations
Across a period (within cations) ionic radius will decrease
Fewer electrons, same number of protons pulling them in
Cations always have a smaller radius than the atoms they formed from

22. Ionic Radii (Cations)

23. Ionic Radius- Anions
Anions form when an atom gains electrons to reach an octet
Overall negative charge
Nonmetals form anions
Down a group, ionic radius of anions increases
More shells of electrons

24. Ionic Radius- Anions Across a period, ionic radius of anions decreases
Anions always have a larger radius than the atoms they came from
Adding electrons to the same number of protons

25. Ionic Radii (Anions)