1. Electron Configurations – a Review and More…

2. Electron Configurations
e- configuration notation:
Reminder – this notation uses # of e- in a sublevel as a superscript over the sublevel (block) designation
Write complete e- configuration notation for element 16

3. Electron Configurations
e- configuration notation (noble gas shortcut):
Reminder – this version uses a noble gas (group 18) “core” instead of beginning at 1s
Write noble gas shortcut for elements 12, 21, & 35.

4. Electron Configurations
e- dot notation:
simplest notation, only shows valence e- (outer shell e- that may be lost, gained, or shared when chemical compounds are formed - they are from s & p blocks)
Draw dot diagrams for elements 1-10

5. Electron Configurations
e- dot notation:
Here are the dot diagrams for elements Note that the group number corresponds to the number of dots the element gets (except for He).
Images are from
for more info

6. Ion Formation…

7. Ion Formation…
Octet rule:
atoms are most stable when they have a filled outer shell of valence e- (usually 8 e-)
noble gases have this configuration without any help – other atoms lose, gain, or share e- to fill their outer shell

8. Ion Formation… Ions: Atoms that have either gained or lost e-.
Gain of e- gives a negative ion called an anion.
Loss of e- gives a positive ion called a cation.

9. Ion Formation… Ion examples:
The magnesium ion is Mg 2+. How many p+ and e- does it have?

10. Ion Formation… Ion examples:
The oxide ion is O 2-. How many p+ and e- does it have?

11. Ion Formation… Ion examples:
An ion has 7 p+ and 10 e-. What ion is it? Give your answer as a dot diagram.

12. Ion Formation… Ion examples:
An ion has 4 p+ and 2 e-. What ion is it? Give your answer as a dot diagram.

13. Bonding

14. Chemical Bonds
link between atoms due to mutual attraction of nuclei for e-

15. Chemical Bonds Why bond???
Bonding can result in lower potential energy (this is usually associated with a release of energy)
Lower energy gives greater stability (greatest completed energy level)

16. Chemical Bonds
Bonds are classified by how the valence e- are distributed around nuclei of combined atoms

17. Types of Chemical Bonds
Ionic bond – results from electrostatic attraction between positive and negative ions (usually done when metal bonds w/ nonmetal)

18. Types of Chemical Bonds
Ionic bond
Created by transfer of e- from one atom to another, creating 2 oppositely charged ions
e- are transferred from atom with lower EN value to one with higher value (usually from a metal to a nonmetal)

19. Types of Chemical Bonds
Ionic bond
How can you determine if bond is ionic?
See if atoms are active metal & non-metal
Look up EN values to get difference
(ionic bond has EN difference from 1.7 to 4.0)

20. Types of Chemical Bonds
Ionic bond
Types of ions
Monoatomic – single element with charge
Polyatomic – 2 or more elements with charge

21. Types of Chemical Bonds
Ionic bond
Ionic compound – composed of positive & negative ions combined so that the positive & negative charges are equal in number (Ex. NaCl instead of Na2Cl or NaCl2)

22. Types of Chemical Bonds
Covalent (molecular) bond – results from the sharing of e- between two atoms (usually done w/ nonmetal atoms)
The e- are not always equally shared (like tug of war)

23. Covalent Bonds
Bonds between 2 unlike atoms are never completely covalent
Non-polar covalent – e- are shared equally ( which only happens between two identical atoms)
Polar covalent – e- are not equally shared (due to differences in electronegativity)

24. Covalent Bonds May share 1 or more pairs of e-
Single bond – single pair of shared e- between two atoms, longest/weakest covalent bond
Double bond – two pairs of shared e- between two atoms
Triple bond – three pairs of shared e- between two atoms, shortest/strongest covalent bond

25. Covalent Bonds
Atoms that are bonded covalently form stable particles called molecules
Ex. CO2, P2O5, NH3, etc.
7 diatomic molecules to know - H2, N2, O2, F2, Cl2, I2, Br2
first 5 are room temp, I2 is a solid, & Br2 is a liquid

26. Covalent Bonds
Molecular compound – chemical compound whose simplest formulas are molecules

27. Comparing Properties…
Ionic Compounds
Held together tightly (due to attraction of charges)
High melting point
High boiling point
Hard & brittle crystalline solids
Dissolve in water
Carry a current (very well) in water

28. Comparing Properties…
Molecular Compounds
Most are not tightly held
Most have low melting point (due to weak attractions between molecules)
Most have low boiling point
Usually soft, amorphous solids
Some dissolve in water
Do not carry current well in water

29. Determining Bond Type…
Using Periodic Table
Metal Element (left of staircase) + Nonmetal Element (right of staircase)
Ionic Bond
Two Nonmetal Elements (right of staircase)
Covalent Bond

30. Determining Bond Type…
Using Electronegativity Values
Page 161 has a EN chart
Determine the EN difference between the two elements in the bond
Go to page 176 and find the chart of bond types. Use the EN difference to determine type of bond (greater difference = more ionic character).
Nonpolar covalent: difference of 0 to 0.3
Polar covalent: difference of 0.3 to 1.7
Ionic: difference of 1.7 to 4.0

31. Determining Bond Type…
Using Observed Properties from Lab Activity
Conducts electricity while dry
Metallic bonding (valence electrons are free to move from one atom to another)
Dissolves in water
Rule for dissolving is “like dissolves like”
Compounds with either polar covalent bonds or ionic bonds (which are very polar bonds) may dissolve because water has polar covalent bonds

32. Determining Bond Type…
Using Observed Properties from Lab Activity
Conducts electricity while dissolved in H2O
Ionic bonds
Dissolving ionic compounds allows ions to separate and this lets electric current flow from one ion to the next

33. Representing Compounds - Ionic
Empirical formula or Formula unit – indicates lowest whole number ratio of cations to anions in any sample of an ionic compound
(ex. NaF = 1 Na+ ion + 1 F- ion)

34. Representing Compounds - Ionic
Empirical formula or Formula unit – simplest unit indicated by the formula of any compound (ex. NaF = 1 Na+ ion + 1 F- ion)
This “unit” doesn’t represent something that can be isolated, it is only the smallest possible ratio to make a neutral electrical charge

35. Representing Compounds - Ionic
Empirical formula or Formula unit – simplest unit indicated by the formula of any compound (ex. NaF = 1 Na+ ion + 1 F- ion)
This “unit” doesn’t represent something that can be isolated, it is only the smallest possible ratio to make a neutral electrical charge
# of ions in one formula unit depends on the charges of the ions to be combined (ex. B + F, Na + Cl, K + O, etc)

36. Representing Compounds - Ionic
Just a thought…
Can you use the periodic table to determine the charge of an ion?
Yes, how many e- are in the outer shell (valence e-).

37. Representing Compounds - Ionic
Determining formula units by the crisscross method
Ca + Br becomes

38. Representing Compounds - Ionic
Determining formula units by the crisscross method
K + P becomes

39. Representing Compounds - Ionic
Determining formula units by the crisscross method
Al + O becomes

40. Representing Compounds - Ionic
Determining formula units by the crisscross method
Ca + O becomes

41. Representing Compounds - Ionic
Determining formula units by the crisscross method
Al3+ + OH1- becomes

42. Representing Compounds - Ionic
Determining formula units by the crisscross method
Mg2+ + PO43- becomes

43. Representing Compounds - Molecular
Molecular formula – shows the types and numbers of atoms combined in a single molecule of a compound
Ex. CO, H2O2, SF2, N2
Chemical formula – shorthand representation of the composition of a substance using atomic symbols and numerical subscripts

44. Representing Compounds - Molecular
Structural formula – shows kind, number, arrangement, and bonds (single, double, or triple) of the atoms in a molecule (or polyatomic ion) Ex

45. Representing Compounds - Molecular
Lewis structures - diagrams that show valence e- as dots, the inner e- and nucleus are included in the letter symbol for the element being represented

46. Representing Compounds - Molecular
Lewis structures
Reminder…
Group 1

47. Representing Compounds - Molecular
Lewis structures
Reminder…
Group 2

48. Representing Compounds - Molecular
Lewis structures
Reminder…
Group 13

49. Representing Compounds - Molecular
Lewis structures
Reminder…
Group 14

50. Representing Compounds - Molecular
Lewis structures
Reminder…
Group 15

51. Representing Compounds - Molecular
Lewis structures
Reminder…
Group 16

52. Representing Compounds - Molecular
Lewis structures
Reminder…
Group 17

53. Representing Compounds - Molecular
Lewis structures
Reminder…
Group 18

54. Representing Compounds - Molecular
Lewis structures
Structures of individual elements may be joined to form compounds
a dash (sometimes a pair of dots instead) between symbols represent bonds (or electron pairs), dots adjacent only to one symbol are unshared e- (also called lone pairs)

55. Representing Compounds - Molecular
Lewis structures
Ex. F2, NH3, H2O, CH4, O2, CO2, N2, CH2O, C2H2, PI3
(must draw structures)

56. Representing Compounds - Molecular
Lewis structures
Octet exceptions:
Less than full octet
Ex: Boron compounds such as BF3

57. Representing Compounds - Molecular
Lewis structures
Octet exceptions:
More than full octet – atoms beyond 2nd period, most often S & P (extra e- go to 3d level)
Ex: SF4