1. Periodic Trends

2. OUTCOME QUESTION(S): C12-2-07 PERIODIC TRENDS Vocabulary & Concepts
Identify factors and account for periodic trends among the properties of elements, and relate to electron configurations.
Include: atomic / ionic radii, ionization energy, and
electronegativity.
Construct Lewis dot diagrams for various compounds and use VSEPR to predict bond shape from the electron arrangement.
Vocabulary & Concepts 
Pauli Exclusion Principle Hund Rule
Aufbau Principle

3. Valence electrons are affected by these 3 factors:
*Atomic properties are controlled by valence electrons *
Valence electrons are affected by these 3 factors:
Nuclear charge - more protons, increased attractive force on valence electrons.
Distance – the further away from the nucleus, the less attractive force.
This is based on Coulomb's Law
Notice less force on the outer electron
3. Shielding Effect - inner electrons shield and
decrease the attractive force for outer electrons.

4. Atomic Radius Decreases Across same quantum (n) level (same distance)
increase proton number (more attraction)
Increases Down
new quantum level
(more distance)
more shielding
(less attraction)
FACT: Nuclear charge has the biggest impact moving across, but distance has the biggest impact moving down

5. Na:
11 p+
11 e-
Cl:
17 e-
17 p+
The increased nuclear charge attracting the same quantum level (n=3) pulls valence electrons inward

6. Note: cations and anions have different factors
2. Ionic Radius
Ion size differs from atom size
Note: cations and anions have different factors
Cations (lost electrons) – smaller radii
increased nuclear attraction (same protons, less electrons)
possible lost quantum (n) level (less distance)
Anions (gained electrons) – larger radii
decreased attraction (same protons, more electrons)
repulsion of extra electrons causes expansion

7. + - Na Cl Cations – smaller radii Anions – larger radii
- increased nuclear attraction decreased nuclear attraction
- possible lost quantum (n) level repulsion of extra electrons causes expansion

8. Gets larger at the jump to Anions….then decreases again
Notice: it is the same basic trend as atomic radius:
Size decreases across…size increases down
Gets larger at the jump to Anions….then decreases again

9. 3. Ionization Energy
Energy required to remove an electron from an atom forming an ion
Removing next electron takes more energy (IE2)
Atom + energy1 → Ion e1−
Ion energy2 → Ion e2−
The amount of energy required depends on the force on the electron – distance, shielding, nuclear charge

10. increase proton number (more attraction)
Increases Across
increase proton number (more attraction)
same quantum (n) level (same distance)
Decreases Down
new quantum level
(more distance)
more shielding
(less attraction)
Think about how/why charge, distance and shielding would affect energy needed to remove an electron

11. Na: nuclear charge is too weak to hold its valence electron – lower IE+ Na Cl
Comparing in a Period:
Na: nuclear charge is too weak to hold its valence electron – lower IE
Cl: nuclear charge is great enough to hold its valence electrons – higher IE

12. Na: distance is small enough to hold its valence electron – higher IE
Comparing in a Column:
Na: distance is small enough to hold its valence electron – higher IE
Cs: distance is too great to hold tight to its valence electrons – lower IE Na Cs

13. 1 valence e-
3 valence e-
6 valence e-
Notice: significantly larger energy needed after the valence shell is emptied
“Subsequent electrons takes more ionization energy”
The largest jumps in IE requirements occur when valence electrons are exhausted and electrons are then removed from closer quantum levels.

14. 4. Electronegativity
Value (from 0 – 4.0) representing attraction an atom has for bonding electrons
bigger the number, “greedier” they are for electrons
Increases Across
increase charge
Increases attractive force
Decreases Down
increase distance
Decreases attractive force

15. Stronger: able to attract your own…and grab after others
WEAKER nuclear charge
STRONGER nuclear charge
Na:
Cl:
Lower ionization energy
Lower Electronegativity
HIGHER ionization energy (yours)
HIGHER Electronegativity (others)
Stronger: able to attract your own…and grab after others

16. These numbers vary slightly depending on the source…
Bond type is less concrete than just ionic, polar and non-polar. It is a spectrum…
These numbers vary slightly depending on the source…
EN Difference
Bond Type
Percent Ionic
less than 0.4
non-polar covalent
0% − 5%
0.4 − 1.9
polar covalent
5% − 60%
greater than 1.9
ionic
> 60%

17. - + Large enough EN difference – create ionic bonds polar covalent
2.1
2.5 H C Cl H
2.1
polar covalent
non-polar covalent
3.0
Greater the EN difference - more polar the bonds
Large enough EN difference – create ionic bonds - +
0.9
3.0

18. Instead of trying to memorize this, understand how the 3 factors relate so you can figure all of this out

19. CAN YOU / HAVE YOU? C12-2-07 PERIODIC TRENDS Vocabulary & Concepts
Identify factors and account for periodic trends among the properties of elements, and relate to electron configurations.
Include: atomic / ionic radii, ionization energy, and
electronegativity.
Construct Lewis dot diagrams for various compounds and use VSEPR to predict bond shape from the electron arrangement.
Vocabulary & Concepts 
Pauli Exclusion Principle Hund Rule
Aufbau Principle