1. Periodic Trends

2. What is a trend?
A trend is a predictable change in a particular direction.
Trends include ionization energy, reactivity, etc.

3. Ionization Energy
The ionization energy is the energy required to remove an electron from an atom or ion
A + ionization energy = A+ + e-
neutral atom = ion + electron

4. Ionization Trend
Ionization energies decrease down a group. (increase up a group)
Ionization energies increase across a period

5. Electron Shielding
As you move down in a group, the number of electrons increase and the energy level increases.
The inner electrons shield the outer shell electrons from the attractive pull of the nucleus
the reduction in the attractive force of the positively charged nucleus and the outermost electrons due to cancellation of some + charges by the e-.

6. Electron Shielding Constants

7. Atomic Radius
Atomic radius is not determined by measuring the radius of one atom, but 1/2 the distance between 2 adjacent nuclei (internuclear distance)
Internuclear distance
Atomic Radius

8. Atomic Radii Trends
Atomic radii increase as you move down a group and decreases as you move across a period.

9. Electronegativity
Electronegativity is the measure of an atom in a chemical compound to attract electrons
Linus Pauling created a chart of electronegativity values

10. Electronegativity Trends
Electronegativity decreases as you move down a group and increases across a period

11. Summary of Periodic Table Trends
Moving Left --> Right
Atomic Radius Decreases
Ionization Energy Increases
Electronegativity Increases
Moving Top --> Bottom
Atomic Radius Increases
Ionization Energy Decreases
Electronegativity Decreases

12. Ions Atoms form ions by either gaining or losing electrons.
Ionic radii decrease across the period and increases down the group

13. Ionic Radius Trends Metals Non-metals HOWEVER:
Ionic radius decreases from left to right.
Ionic radius increases down the chart
Non-metals
Ionic radius decreases from left to right
HOWEVER:
Non-metallic ions are larger than metallic ions
Decrease across the row, until you reach the non-metals

14. Electron Affinity
The energy change that occurs when a neutral atom gains an electron is electron affinity
Electron affinity increases across a period and decreases down a group