1. Periodic Patterns
Unit 4 – Periodic Table

2. Lesson Essential Question:
What patterns exist on the periodic table?

3. METALLIC TREND
INCREASES
INCREASES

4. ATOMIC RADIUS
Radius is the distance from the center of the nucleus to the “edge” of the electron cloud.
Atomic radii are usually measured in picometers (pm) or angstroms (Å). An angstrom is
1 x m.

5. ATOMIC RADIUS
Since a cloud’s edge is difficult to define, scientists use define covalent radius, or half the distance between the nuclei of 2 bonded atoms.
BROMINE = Br2
2.86 Å
1.43 Å
1.43 Å

7. ATOMIC RADII TRENDS WHY? INCREASES
DOWN A FAMILY OR GROUP
WHY?
INCREASES
As you go down a family the n value increases making the radius larger.

8. ATOMIC RADII TRENDS WHY? DECREASES
ACROSS A PERIOD
WHY?
As you go across a period the number of protons increases, (nuclear charge) pulling the electrons in tighter making the radius smaller.

9. IONS - remember Metals Nonmetals Lose electrons becoming positive.
Calcium – Ca
[Ar]4s2
Loses 4s2 e-s becoming
Ca+2 and [Ar] Noble gas
Configuration (Octet Rule)
Nonmetals
Gain electrons becoming negative.
Chlorine – Cl
[Ne]3s23p5
Gains one e- becoming Cl-1 and [Ar] Noble gas configuration.
(Octet Rule)

10. IONS – How can I remember?
Metals
Nonmetals
This is Cat-ion - CATION
This is Ann ion - ANION
He is a “plussy” cat!
She is unhappy and negative.

11. IONIC RADII TRENDS WHY? INCREASES
DOWN A FAMILY OR GROUP
WHY?
INCREASES
As you go down a family the n value increases making the radius larger.

12. IONIC RADII TRENDS
DECREASES then INCREASE
ACROSS A PERIOD
WHY?
For the metals the nuclear charge is greater than then number of electrons pulling them in tighter making the radius smaller.
At the nonmetals the radius gets larger because the ion has gained electrons.

13. METALLIC ATOM AND ION COMPARISON

14. NONMETALLIC ATOM AND ION COMPARISON
Why do the Noble Gases not have an ionic Radius?

15. ATOM AND ION COMPARISON
Why does Hydrogen not have an ionic Radius?

16. Shielding Effect
As more electrons are added to atoms, the inner layers of electrons shield the outer electrons from the nucleus.
The effective nuclear charge on those outer electrons is less, and so the outer electrons are less tightly held

17. Example of Shielding Effect

18. Ionization Energy
The energy required to remove an electron from an atom is ionization energy. (measured in kilojoules, kJ)

19. IONIZATION ENERGY
The larger the atom is, the easier its electrons are to remove.
Ionization energy and atomic radius are inversely proportional.
Ionization energy is always endothermic, that is energy is added to the atom to remove the electron.

21. IONIZATION TREND
INCREASES
INCREASES

22. Electron Affinity
is a measure of the energy change when an electron is added to a neutral atom to form a negative ion

23. ELECTRON AFFINITY
Why do the Alkaline Earth Metals and Noble Gases not have measurable Electron Affinities?

24. Electronegativity
is a measure of the tendency of an atom to attract a bonding pair of electrons.

25. ELECTRONEGATIVITY

27. In Summary….
Electronegativity
Electronegativity