1. From Atoms to Compounds (Chapters 7-9)
Dr. Walker

2. Objectives
Determine valence electrons and ionic charge of elements based on placement on the periodic table
Determine names and formulas of compounds using IUPAC naming rules
Differentiate between ionic and covalent compounds based on elemental composition and physical properties

3. More on Electrons Valence Electrons
Electrons in the outer shell of an atom
Determines chemical properties

4. Determining Valence Electrons
How do we determine valence electrons?
Valence electrons = last number of group number
Examples
Sodium – Group 1 = 1 valence electron
Boron – Group 13 = 3 valence electrons
Chlorine – Group 17 = 7 valence electrons
Nitrogen – Group 15 = 5 valence electrons

5. Determining Valence Electrons
We can also get valence electrons from the electron configuration
Examples
Sodium – 1s22s22p63s1 = 1 valence electron
There is one electron in the third energy level
Boron – 1s22s22p1 = 3 valence electrons
There are three electrons in the second energy level
Chlorine – 1s22s22p63s23p5 = 7 valence electrons
There are seven electrons in the third energy level
The electrons in s and p subshells of a given energy level are valence electrons

6. Determining Valence Electrons
What about the transition metals, actinides, and lathanides?
We don’t worry about these elements
These elements can use electrons from d and f orbitals, which we won’t deal with

7. The Octet Rule
Every main group element wants to have eight valence electrons
Main groups = 1-2, 13-18
Not transition metals, inner transition metals
Can lose d or f electrons to gain stability

8. But wait… Not all elements have eight valence electrons
Only the noble gases (group 18) has eight valence electrons
So how does an element obey the octet rule?

9. From Atoms to Ions
Ion
An atom that has gained or lost one or more electrons
This species is now charged
Cation – positively charged (loses electrons)
Anion – negatively charged (gains electrons)

10. From Atoms to Ions
Atoms will gain or lose electrons to obey the octet rule
Example
Sodium has 1 valence electron in level 3
It can either gain 7 electrons to fill level 3 or lose the electron in level 3, making level 2 the valence shell.

11. From Atoms to Ions
The second energy level is now the valence shell for sodium

12. From Atoms to Ions
Notice sodium started with 11 protons (+) and 11 electrons (-). This was a neutral atom.
After losing an electron, the sodium ion has 11 protons (+) and 10 electrons (-). There is one extra proton, so the charge is +1.

13. From Atoms to Ions
Chlorine has 7 valence electrons. It can either gain 1 electron or lose 7 electrons. It is easier to gain 1 electron

14. From Atoms to Ions
Chlorine starts with 17 protons (+) and 17 electrons (-) and was neutral
When chlorine gains an electron, it has 17 protons (+) and 18 electrons (-)
Chlorine now has an extra electron, giving it a charge of -1.

15. Valence Electrons and Charge
Group 1 2 13 14 15 16 17 18
Valence Electrons 3 4 5 6 7 8
Lose or Gain
Lose 1
Lose 2
Lose 3
Either/or
Gain 3
Gain 2
Gain 1
Neither
Charge +1 +2 +3
+4 or -4 -3 -2 -1
Keep in mind:
-Losing electrons gives you a positive charge because you are
losing negative charges.
-Gaining electrons gives you a negative charge
This is the concept that confuses students the most!
-Only electrons will EVER be gained or lost!!!

16. Exercises How many valence electrons are in nitrogen?
What will its charge be?
How many protons and electrons will be present at this time?

17. Exercises How many valence electrons are in nitrogen?
5 (group 15)
What will its charge be?
It must gain 3 electrons, so it will be -3
How many protons and electrons will be present at this time?
7 protons (atomic # = 7)
10 electrons (had 7, gained 3, = 10)

18. Exercises How many valence electrons are in calcium?
What will its charge be?
How many protons and electrons will be present at this time?

19. Exercises How many valence electrons are in calcium?
2 (group 2)
What will its charge be?
Needs to lose two electrons, so +2
How many protons and electrons will be present at this time?
20 protons (atomic #)
18 electrons (had 20, lost 2, 20 – 2 = 18)

20. Notice the trend?
When atoms gain or lose electrons, they will have the same number of electrons as one of the noble gases and will have a noble gas electron configuration
Losing or gaining electrons changes the electron configuration
Sodium (neutral): 1s22s22p63s1
Sodium (cation, +1 charge): 1s22s22p6
Notice the sodium has 10 electrons now, which is the same number of electrons as neon

21. Summary
Valence electrons are determined by the group number and electron configuration
Octet Rule: All main group elements want eight valence electrons
Atoms gain or lose electrons to obey the octet rule. This results in a charge. A charged atom is known as an ion.

22. A question…. If cations lose electrons, where do they go?
Don’t’ write!!
A question….
If cations lose electrons, where do they go?
If anions gain electrons, where do they come from?

23. Ionic Bonding
Ionic bonds are formed when ions transfer electrons to obey the octet rule
Ionic bonds between elements result in the formation of compounds
The net charge of all compounds is zero

24. Ionic Bonding
Ionic bonding occurs between elements that form opposite charges upon bonding
These atoms will be on opposite sides of the periodic table staircase
One atom from the left, one from the right
One metal, one nonmetal

25. Ionic Bonding
This diagram shows the transfer of an electron from sodium to chlorine
A sodium cation and chloride anion are formed in this process
The two ions together form a neutral compound

26. Ionic Bonding
This shows an example of multiple electrons being transferred
Each chlorine needs to gain one electron
Calcium loses two electrons, donating one to each chlorine

27. Rule stating everyone wants
Eight valence electrons
Atoms lose electrons
to form __________
Atoms gain electrons to form __________
Combines
To form
_________ bonds
Results from the __________ of electrons

28. Rule stating everyone wants
Eight valence electrons
Octet rule
Atoms lose electrons
to form cations
Atoms gain electrons to form anions
Combines
To form
Ionic bonds
Results from the transfer of electrons

29. What is a Formula?
A chemical formula shows the numbers of atoms of each element in the smallest representative unit of a substance.
Formulas are used to represent compounds
Examples
NaCl (1 sodium, 1 chlorine)
H2O (2 hydrogens, 1 oxygen)
C6H12O6 (6 carbons, 12 hydrogens, 6 oxygens)

30. Formula Unit Chemical formula of an ionic compound
Ionic compounds exist in networks
Formula unit shows the lowest number ratio
Example: LiCl – Li loses 1 electron, Cl gains 1 electron, formula unit is LiCl
Diagram shown is the crystal structure which shows a large network
Lithium and chlorine still have 1:1 ratio

31. Ionic Formulas
You can figure out the formula for an ionic compound by criss-crossing charges to subscripts and reducing subscripts if possible
The formulas are determined so that (+) charge = (-) charge
The overall charge MUST be zero!!!!!

32. Ionic Formulas
You figure out the formula for an ionic compound by criss-crossing charges to subscripts and reducing subscripts if possible.
Na+1 Cl-1
K+1 O-2
Mg+2 P-3

33. Ionic Formulas
You figure out the formula for an ionic compound by criss-crossing charges to subscripts and reducing subscripts if possible.
Na+1 Cl NaCl
K+1 O K2O
Mg+2 P Mg3P2

34. More Ionic Examples Give the formula for the following Ca+2 and N-3
Mg+2 and F-1
Li+1 and S-2
Al+3 and O-2

35. More Ionic Examples Give the formula for the following Ca+2 and N-3
Ca3N2
Mg+2 and F-1
MgF2
Li+1 and S-2
Li2S
Al+3 and O-2
Al2O3

36. Polyatomic Ions
Group of atoms that are covalently bound with a singular charge
Makes ionic bonds like any other ion
Ones to know
Nitrate, NO3-
Ammonium, NH4+
Hydroxide, OH-
Sulfate, SO4-2
Carbonate, CO3-2
Phosphate, PO4-3

37. Polyatomic Examples Na+1 and CO3-2 NH4+1 and Cl-1 Ca+2 and PO4-3
Al+3 and SO4-2

38. Polyatomic Examples Na+1 and CO3-2 NH4+1 and Cl-1 Ca+2 and PO4-3
Na2CO3
NH4+1 and Cl-1
NH4Cl
Ca+2 and PO4-3
Ca3(PO4)2
Al+3 and SO4-2
Al2(SO4)3
Need parentheses around multiple polyatomic ions

39. Naming Ionic Compounds
Rules for naming made by IUPAC
International Union of Pure and Applied Chemistry
Write the name of the cation.
If the anion is an element, change its ending to -ide; if the anion is a polyatomic ion, simply write the name of the polyatomic ion.
Ca3N2
MgF2
Na2CO3
Al2(SO4)3

40. Naming Ionic Compounds
Write the name of the cation.
If the anion is an element, change its ending to -ide; if the anion is a polyatomic ion, simply write the name of the polyatomic ion.
Ca3N2 = Calcium nitride
MgF2 = Magnesium fluoride
Na2CO3 = Sodium carbonate
Al2(SO4)3 = Aluminum Sulfate

41. Transition Metals Transition metals do not follow the octet rule
Transition metals can have multiple charges
The charge of a transition metal is designated by a roman numeral
Reverse the arrows to determine the charge on the metal, then name accordingly
Examples
FeCl2
FeCl3
Cu2O
CuO

42. Transition Metals Transition metals do not follow the octet rule
Transition metals can have multiple charges
The charge of a transition metal is designated by a roman numeral
Reverse the arrows to determine the charge on the metal, then name accordingly
Examples
FeCl2 = Iron (II) chloride
FeCl3 = Iron (III) chloride
Cu2O = Copper (I) oxide
CuO = Copper (II) oxide

43. From Name to Formula Determine charges on ions
Reverse arrows accordingly
Name doesn’t tell you how many atoms are present
Example
Potassium sulfide

44. From Name to Formula Determine charges on ions
Reverse arrows accordingly
Name doesn’t tell you how many atoms are present
Example
Potassium sulfide
K S-2
K2S

45. From Name to Formula More Examples Aluminum hydroxide Lithium nitride
Magnesium sulfate
Calcium chloride

46. From Name to Formula More Examples Aluminum hydroxide Lithium nitride
Al(OH)3
Lithium nitride
Li3N
Magnesium sulfate
MgSO4
Calcium chloride
CaCl2

47. From Name to Formula Lead (IV) oxide Copper (I) sulfate
Iron (II) chloride
Potassium phosphate

48. From Name to Formula Lead (IV) oxide PbO2 Copper (I) sulfate Cu2SO4
Iron (II) chloride
FeCl2
Potassium phosphate
K3PO4

49. More Examples

50. More Examples

51. Covalent Bonding
Covalent bonding results from the sharing of electrons
Forms molecular compounds
Ionic bonding occurs from the transfer of electrons
Ionic bonding occurs between ions with opposite charges
Covalent bonding occurs between atoms that need electrons to fill their octets

52. Covalent Bonding
Naming covalent compounds:
Use prefixes

53. Covalent Bonding Name to Formula
Give the formula for the following compounds:
Carbon tetrachloride
Dinitrogen tetroxide
Nitrogen monoxide
Phosphorous trifluoride

54. Covalent Bonding Naming Molecular Compounds
Give the formula for the following compounds:
Carbon tetrachloride
CCl4
Dinitrogen tetroxide
N2O4
Nitrogen monoxide NO
Phosphorous trifluoride
PF3

55. Covalent Bonding
Formula to Name:
SO2
N2O3
SiBr4
NCI3

56. Covalent Bonding Formula to Name: SO2 N2O3 SiBr4 NCl3 Sulfur dioxide
Dinitrogen trioxide
SiBr4
Silicon tetrabromide
NCl3
Nitrogen trichloride

57. Compare and Contrast Ionic Bonding Elements have opposite charges
One element gains electrons, one loses electrons
Found on opposite sides of the staircase of the periodic table
Includes transition metals and polyatomic ions
Large electronegativity difference between atoms

58. Compare and Contrast Covalent Bonding
Both elements found on right side of “the staircase” (exception: Hydrogen uses covalent bonds)
No metals!!!
Remember, hydrogen is a gas, NOT a metal!
Small electronegativity difference between atoms

59. Compare and Contrast Ionic Covalent
Mostly crystalline solids at room temperature (very high melting points)
Ionic salts dissolved in water conduct electricity
Covalent
Can be liquids or gases at room temperature
Poor or non-conducting

60. Rule stating everyone wants Eight valence electrons
Valence shell filled by transfer
Valence shell filled by sharing
Elements
Used
Elements
Used
How to name
How to name
Includes
Which one conducts
electricity? ___________
Ends in ________
_________ shows charge

61. Rule stating everyone wants Eight valence electrons Octet rule
Valence shell filled by transfer
Valence shell filled by sharing
ionic
covalent
Elements
Used
Elements
Used
How to name
How to name
Metal + nonmetal
No prefixes
Use prefixes
Nonmetals only
Includes
Which one conducts
electricity? ___ionic_
Polyatomic ions
Transitional metals
Roman numeral shows charge
Ends in –ate or -ite

62. Review Electronegativity
The tendency of an atom to attract electrons to itself when chemically combined with another element
Increases to the right on the Periodic Table
Increases going up on the Periodic Table
Most electronegative elements: F, O, Cl

63. http://www. cusd. chico. k12. ca

64. Ionic or Covalent?
Are the following compounds ionic or covalent? What are they called?
KCl
H2O
Fe(OH)2
MgBr2
P2O5

65. Ionic or Covalent?
Are the following compounds ionic or covalent? What are they called?
KCl Ionic; Potassium chloride
H2O Covalent; Dihydrogen monoxide (aka water)
Fe(OH)2 Ionic; Iron (II) hydroxide
MgBr2 Ionic; Magnesium bromide
P2O5 Covalent; Diphosphorous pentoxide

66. Review
How many valence electrons does nitrogen have? When it ionizes, what is its charge? After it ionizes, how many protons and electrons does it have?
What is the formula for calcium hydroxide?
What is the name of P2O4?
Is Iron (III) sulfate an ionic or covalent compound?

67. Review How many valence electrons does nitrogen have? 5
When it ionizes, what is its charge? -3
After it ionizes, how many protons and electrons does it have? 7 protons, 10 electrons
What is the formula for calcium hydroxide? Ca(OH)2
What is the name of P2O4? Diphosphorous tetroxide
Is Iron (III) sulfate an ionic or covalent compound?
Ionic; it involves a transition metal and a polyatomic ion

68. Terms to Know Valence Electrons Octet Rule Cation Anion
Chemical Formula
Formula Unit
Ionic Bond
Covalent Bond
Polyatomic Ion
Electronegativity

69. Skills To Master Determining Valence Electrons From the periodic table
From electron configuration
Determining charge
From numbers of subatomic particles
Determine the formula of a compound from its name
Differentiate ionic and covalent compounds from name or formula
Determine the name of a compound from its formula based on its bonding type (ionic or covalent)