1. CHEMISTRY Trends and Configurations

2. Electron Configurations and the Periodic Table
Valence electron configurations repeat down a group

3. Ground state electron configurations
Example: Li
atomic number = 3
nucleus has 3 protons
neutral atom has 3 electrons
2 electrons in 1s orbital, 1 electron in 2s orbital 2s 1s

4. Different ways to show electron configuration
Energy level diagram
Box notation   2s 1s 2s 1s
Spectroscopic notation
Li 1s2 2s1
Read this “one s two” not “one s squared”
Write the superscript 1. Don’t leave it blank

5. Using the Periodic Table
The last subshell in the electron configuration is one of these
(row #) s (row # – 1) d
(row #) p (row # – 2) f

6. The f-block is inserted into to the d-block

7. Electron configuration of O
Atomic number of O = 8 so neutral atom has 8 e–

8. Electron configuration of Co
Atomic number of Co = 27 so neutral atom has 27 e–

9. Simplifying electron configurations Shorthand Noble Gas Configuration    
Build on the atom’s noble gas core
He 1s2
O 1s22s22p4
O [He]2s22p4
Ar 1s22s22p63s23p6
Co 1s22s22p63s23p64s23d7
Co [Ar]4s23d7 1s 2s 2p                1s 2s 2p 3s 3p 4s 3d

10. Noble Gas electron configurations
What is the electron configurations for Neon
Abbreviated way to write configurations
Start with full outer shell then add on Br Ba

11. Why are we doing all of this?
Properties of atoms correlate with the number and energy of electrons
Electron configurations are used to summarize the distribution of electrons among the various orbitals

12. Electron configuration of ions
What is an ion?
How many electrons does Cl1- have?
What is the electron configuration for the chloride ion?
How many electrons does Ca2+ have?
What is the electron configuration for the calcium ion?
What do you notice?

13. Why is this important Valence electrons
Electrons in the outermost energy level
Where all the action occurs

14. The f-block is inserted into to the d-block

15. Find the electron configuration of Au
Locate Au on the periodic table

16. Find the electron configuration of Au
Au [Xe]
The noble gas core is Xe

17. Find the electron configuration of Au
Au [Xe]6s2
The noble gas core is Xe
From Xe, go 2 spaces across the s-block in the 6th row  6s2

18. Find the electron configuration of Au
Au [Xe]6s24f14
The noble gas core is Xe
From Xe, go 2 spaces across the s-block in the 6th row  6s2
Then detour to go 14 spaces across the f-block  4f14
note: for the f-block, n = row – 2 = 6 – 2 = 4

19. Find the electron configuration of Au
Au [Xe]6s24f145d9
The noble gas core is Xe
From Xe, go 2 spaces across the s-block in the 6th row  6s2
Then detour to go 14 spaces across the f-block  4f14
note: for the f-block, n = row – 2 = 6 – 2 = 4
Finally go 9 spaces into the d-block on the 6th row  5d9
note: for the d-block, n = row – 1 = 6 – 1 = 5

20. Practice Draw the orbital diagram for sulfur.
What ion does sulfur want to form and why?
Draw the orbital diagram for Potassium.

21. Periodic Trends

22. Preview 4 Periodic Trends 2 main factors affect periodic trends
Atomic Size/Radius
Ionic Size (**)
Ionization Energy
Electronegativity
2 main factors affect periodic trends
Number of electron shells (group)
Effective Nuclear Charge (period)

23. Periodic Trends Atomic radius
The distance from the center of an atoms nucleus to it’s outermost electron
Measure of atomic size

24. Periodic Trends

25. Atomic Radius Group Trend Period Trend Increases from top to bottom
More energy levels or quantum levels (or “shell”) as you go down a group – atomic radius increases
Period Trend
Decreases from left to right
All electrons in the same energy level. Increased # of protons holds them closer to nucleus.

26. Table of Atomic Radii

27. Period Trend: Atomic Radius

28. Periodic Trends Size of an atom when electrons are added or removed.
Electrons removed atom becomes smaller.
Electrons added atoms become larger
Why?
Electron-Electron Repulsion
Ionic Size

29. Ionic Size Cations Anions Positively charged ions formed when
an atom of a metal loses one or
more electrons
Cations
Smaller than the corresponding
atom
Negatively charged ions formed
when nonmetallic atoms gain one
or more electrons
Anions
Larger than the corresponding
atom

30. Table of Ion Sizes

31. Ionic Size Group Trend Period Trend Increases from top to bottom
More energy levels as you go down a group – ionic size increases
Period Trend
Decreases as atoms lose more electrons
Increases dramatically as atoms start gaining electrons, decreases as atoms gain fewer electrons.

32. Periodic Trends Ionization Energy
Energy needed to remove one of the electrons on an atom’s outer shell.
How strongly does an atom hold it’s outermost electron.

33. Graph the first 20 elements. What is the trend down a group
Graph the first 20 elements. What is the trend down a group? Across a Period?

34. Ionization Energy Group Trends Period Trend
Decreases from top to bottom.
Shielding makes electrons easier to remove.
Period Trend
Increases from left to right.
Increased Effective Nuclear Charge makes it harder to remove electrons.

35. Periodic Trend: Ionization Energy

36. Periodic Trends Electronegativity
Is a measure of the level of attraction (pull) an atom exerts on the electrons of another atom.
Ability of an atom to attract electrons
Which elements want to gain electrons the most?

37. Graph the first 20 elements. What is the trend down a group
Graph the first 20 elements. What is the trend down a group? Across a Period?

38. Periodic Table of Electronegativities

39. Electronegativity Group Trend Period Trend
Decreases from top to bottom.
As radius increases, electrons are farther to the nucleus (increase in number of electron shells, Shielding effect)
Period Trend
Increases from left to right
Increased Effective Nuclear Charge means the atom wants to attract more electrons.
Exception: Trend does not apply to Noble Gases

40. Periodic Trend: Electronegativity

41. Summary of Periodic Trends

42. Practice Se and Br P, S, Se Cl, Cl1-, Br, Br1- Mg, Mg2+, Na, Na1+
Smallest atom
Lowest Ionization Energy
P, S, Se
Largest atom
Highest Ionization Energy
Cl, Cl1-, Br, Br1-
Largest ionic size
Mg, Mg2+, Na, Na1+
Smallest ionic size

43. Atomic Properties Definitions
Ionization Energy:
Energy needed to remove an electron from an atom or molecule.
The higher the effective core charge and lower the number of electrons shells, the greater the ionization energy
Atomic size
How big (e.g., radius) an atom is
Atomic radius is measured from the center of the nucleus to the valence electron shell.
The higher the effective core charge and lower the number of electron shells, the smaller the atom.
Electronegativity
Measure of the level of attraction (pull) an atom exerts on the electrons of another atom.
The higher the effective core charge and lower the number of electron shells, the greater the electronegativity