1. Graph #1: Atomic Radius vs. Atomic Number
Atomic radius decreases with increasing atomic number…

2. Graph #2: Period vs. Atomic Radius
Atomic radius increases as you go down a period…

3. Graph #3: Ionization Energy vs. Atomic Number
Ionization energy generally increases with atomic number, or from left to right (within a period)…

4. Graph #4: Ionization Energy vs. Period (see Graph #3)

5. Periodic Trends

6. Periodic Law Example: Group 2
When elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals.
All the elements in a group have the same electron configuration in their outermost shells (same # of valence electrons)
Example: Group 2
Be 2, 2
Mg 2, 8, 2
Ca 2, 2, 8, 2

7. Chemical Reactivity Within a group or family:
Increases as you go down within a group for metals
Decreases as you go down within a group for nonmetals

8. Atomic Radius Increases to the LEFT and DOWN Atomic Radius
© 1998 LOGAL
Atomic Radius
Increases to the LEFT and DOWN

9. Melting/Boiling Point
Highest in the middle of a period.

10. Ions Some compounds are composed of particles called “ions”
An ion is an atom (or group of atoms) that has a positive or negative charge
Atoms are neutral because the number of protons equals electrons
Positive and negative ions are formed when electrons are transferred (lost or gained) between atoms

11. Metals tend to LOSE electrons, from their outer energy level
Ions
Metals tend to LOSE electrons, from their outer energy level
Sodium loses one: there are now more protons (11) than electrons (10), and thus a positively charged particle is formed = “cation”
The charge is written as a number followed by a plus sign: Na1+
Now named a “sodium ion”

12. Nonmetals tend to GAIN one or more electrons
Ions
Nonmetals tend to GAIN one or more electrons
Chlorine will gain one electron
Protons (17) no longer equals the electrons (18), so a charge of -1
Cl1- is re-named a “chloride ion”
Negative ions are called “anions”

13. Ion Period Trends
Ion size
Increases to the LEFT and DOWN

14. Ionization Energy
Ionization energy is the amount of energy required to completely remove an electron (from a gaseous atom).
Removing one electron makes a 1+ ion.
The energy required to remove only the first electron is called the first ionization energy.

15. Trends in Ionization Energy
Increases UP and to the RIGHT

16. Electronegativity
Electronegativity is the tendency for an atom to attract electrons to itself when it is chemically combined with another element.
They share the electron, but how equally do they share it?
An element with a big electronegativity means it pulls the electron towards itself strongly!

17. Trends in Electronegativity
Increases UP and to the RIGHT

18. SUMMARY:
Ionization energy and Electronegativity INCREASE in these directions

19. Atomic size and Ionic size increase in these directions:

20. ALL Periodic Table Trends
Influenced by three factors:
1. Energy Level
Higher energy levels are further away from the nucleus.
2. Charge on nucleus (# protons)
More charge pulls electrons in closer. (+ and – attract each other)
3. Shielding effect

21. Shielding
The electron on the outermost energy level has to “look through” all the other energy levels to see the nucleus.