1. Chemical Bonds

2. Atom – the smallest unit of matter “indivisible”
Helium
atom

3. electron shells Atomic number = number of Electrons
Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.
Electron shells determine how an atom behaves when it encounters other atoms

4. Electrons are placed in shells according to rules:
The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons.

5. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons
C would like to
N would like to
O would like to
Gain 4 electrons
Gain 3 electrons
Gain 2 electrons

6. Why are electrons important?
Elements have different electron configurations
different electron configurations mean different levels of bonding

8. Electron Dot Structures
Symbols of atoms with dots to represent the valence-shell electrons
H He:
          
Li Be  B   C   N   O  : F  :Ne :
       
          
Na Mg  Al  Si  P S :Cl  :Ar :
       

9. Chemical bonds: an attempt to fill electron shells
Ionic bonds –
Covalent bonds –
Metallic bonds

10. Learning Check A. X would be the electron dot formula for
A. X would be the electron dot formula for
1) Na 2) K 3) Al
 
B  X  would be the electron dot formula
1) B 2) N 3) P

11. IONIC BOND bond formed between two ions by the transfer of electrons

12. Formation of Ions from Metals
Ionic compounds result when metals react with nonmetals
Metals lose electrons to match the number of valence electrons of their nearest noble gas
Positive ions form when the number of electrons are less than the number of protons
Group 1 metals  ion 1+
Group 2 metals  ion 2+
Group 13 metals  ion 3+

13. Formation of Sodium Ion
Sodium atom Sodium ion
Na  – e  Na +
( = Ne)
11 p p+
11 e e-

14. Formation of Magnesium Ion
Magnesium atom Magnesium ion 
Mg  – 2e  Mg2+
(=Ne)
12 p p+
12 e e-

15. Some Typical Ions with Positive Charges (Cations)
Group 1 Group 2 Group 13
H+ Mg2+ Al3+
Li+ Ca2+
Na+ Sr2+
K+ Ba2+

16. Learning Check A. Number of valence electrons in aluminum
1) 1 e ) 2 e- 3) 3 e-
B. Change in electrons for octet
1) lose 3e ) gain 3 e ) gain 5 e-
C. Ionic charge of aluminum
1) ) ) 3+

17. Solution A. Number of valence electrons in aluminum 3) 3 e-
B. Change in electrons for octet
1) lose 3e-
C. Ionic charge of aluminum
3) 3+

18. Learning Check Give the ionic charge for each of the following:
A. 12 p+ and 10 e-
1) 0 2) 2+ 3) 2-
B. 50p+ and 46 e-
1) 2+ 2) 4+ 3) 4-
C. 15 p+ and 18e-
2) ) 3- 3) 5-

19. Ions from Nonmetal Ions
In ionic compounds, nonmetals in 15, 16, and 17 gain electrons from metals
Nonmetal add electrons to achieve the octet arrangement
Nonmetal ionic charge:
3-, 2-, or 1-

20. Fluoride Ion     1 - : F  + e : F :     2-7 2-8 (= Ne)
unpaired electron octet
   
: F  e : F :
   
(= Ne)
9 p p+
9 e e-
ionic charge

21. Ionic Bond
Between atoms of metals and nonmetals with very different electronegativity
Bond formed by transfer of electrons
Produce charged ions all states. Conductors and have high melting point.
Examples; NaCl, CaCl2, K2O

23. Ionic Bonds: One Big Greedy Thief Dog!

24. 1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

26. COVALENT BOND bond formed by the sharing of electrons

27. Covalent Bond
Between nonmetallic elements of similar electronegativity.
Formed by sharing electron pairs
Stable non-ionizing particles, they are not conductors at any state
Examples; O2, CO2, C2H6, H2O, SiC

28. Covalent Bonds

29. Bonds in all the polyatomic ions and diatomics are all covalent bonds

30. when electrons are shared equally
NONPOLAR COVALENT BONDS
when electrons are shared equally
H2 or Cl2

31. 2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons.
Oxygen Atom
Oxygen Atom
Oxygen Molecule (O2)

32. when electrons are shared but shared unequally
POLAR COVALENT BONDS
when electrons are shared but shared unequally
H2O

33. Polar Covalent Bonds: Unevenly matched, but willing to share.

34. - water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

35. Hydrogen Bond
“Hydrogen bond" implies, one part of the bond involves a hydrogen atom. The hydrogen must be attached to a strongly electronegative heteroatom, such as oxygen, nitrogen or fluorine, which is called the hydrogen-bond donor.

37. METALLIC BOND bond found in metals; holds metal atoms together very strongly

38. Metallic Bond Formed between atoms of metallic elements
Electron cloud around atoms
Good conductors at all states, lustrous, very high melting points
Examples; Na, Fe, Al, Au, Co

39. Metallic Bonds: Mellow dogs with plenty of bones to go around.

40. Ionic Bond, A Sea of Electrons

41. Metals Form Alloys Metals do not combine with metals. They form
Alloys which is a solution of a metal in a metal.
Examples are steel, brass, bronze and pewter.

42. Formula Weights Formula weight is the sum of the atomic masses.
Example- CO2
Mass, C + O + O
43.999

43. Practice What is the type of bond and what is the formula weight?
Na2O
CH4
CO2
K2O
MgO

44. Practice
Compute the mass of the following compounds round to nearest tenth & state type of bond:
NaCl;
= 58; Ionic Bond
C2H6;
= 30; Covalent Bond
Na(CO3)2;
23 + 2( x16) = 123; Ionic & Covalent

45. Formulas and Names of Binary Metal-Nonmetal Compounds
The name of the metal is first (ie: NaCl, sodium chloride)
The name of the nonmetal has -ide added (ie: NaCl sodium chloride)
IF the metal has more than one possible charge
-indicate which ion using the charge in roman numerals (ie: FeCl2 Iron (II) chloride).

46. Cu2S
Name the first ion. Since it is a transition metal, you must use a Roman Numeral.
Which Roman Numeral? The Roman Numeral is the same as the charge of the ion.
How do you find the charge?
Deductive reasoning!
All compounds are neutral
Sulfur has a -2 charge (group 16)
There are two coppers.
Therefore each copper must have a +1 charge for all ions to be neutral
Copper I
Sulfide

47. Another Example: MnO2
Name the first ion. Since it is a transition metal, you must use a Roman Numeral.
How do you determine the Roman Numeral?
It is the same as the charge.
What is the charge of Mn?
All compounds are neutral.
Oxygen (group 16) has a -2 charge.
There are two oxygens and one Mn.
Therefore Mn must have a +4 charge for this compound to be neutral.
Manganese IV
oxide

48. You need to remember the charges for these.
There are three transition elements which do not require a Roman Numeral because they have single definite charges. These are
Zinc – Zn+2
Cadmium – Cd+2
Silver – Ag+1
You need to remember the charges for these.
No Roman Numerals needed for these.
Ag2O
Name the first ion.
Name the second ion changing the suffix to –ide.
Silver
oxide
ZnCl2
Name the first ion.
Zinc
chloride
Name the second ion changing the suffix to –ide.

49. How do you write formulas for binary ionic compounds given the name?
Two simple steps:
Write the symbol and charge of each ion
Balance the charges by providing subscripts to tell how many of each atom is present.
Magnesium chloride
Mg Cl-1
Cl-1
You need a second Cl-1 to balance the charges
MgCl2

50. FeBr3 More examples: Iron III bromide
Write the symbol and charge of each ion. The charge of the iron is provided by the Roman Numeral.
Fe Br -1
Br -1
Br -1
FeBr3
Balance the charges by supplying subscripts. The subscripts tell how many of each ion is needed to balance the compound.
You’ll need three bromine ions to balance the one iron.

51. Al2S3 Aluminum Sulfide Write the symbol and charge of each ion.
Balance the charges by supplying subscripts.
S-2
In this case the charges do not evenly divide into each other. You must find the least common multiple. SIX
Al2S3
How many aluminums are needed to arrive at a +6 charge? 2
How many sulfurs are needed to arrive at a -6 charge? 3

52. You need to learn these!!! CO3-2 carbonate
This ion is composed of one carbon and three oxygens and the entire group has a charge of -2.
Polyatomic ion – Group of atoms that act as a unit and carry a charge.
More examples:
PO4-3
Phosphate
C2H3O2-1
Acetate
SO4-2
Sulfate
OH-1
Hydroxide
SO3-2
Sulfite
NO3-1
Nitrate
ClO4-1
Perchlorate
NO2-1
Nitrite
ClO3-1
Chlorate
NH4+1
Ammonium
(only positive PI)
ClO2-1
Chlorite
ClO-1
Hypochlorite
You need to learn these!!!

53. A few more examples:
Fe(OH)3
Name the first ion.
Iron
III
hydroxide
Remember that iron requires a Roman Numeral since it is a transition element. What Roman Numeral should be used?
Since there are 3 OH groups, each with a -1 charge, the charge of the iron must be +3 for the compound to be neutral
The Roman Numeral comes from the charge of the ion. How do you find the charge of the iron?
You know two things:
All compounds are neutral.
You know the charge of OH (-1)
Name the polyatomic ion.

54. NH4Cl
Name the first ion.
Ammonium
chloride
Name the second ion.
Notice that since the second ion is a nonmetal that, like binary ionic compounds, the suffix of the nonmetal changes to –ide.
Name the first ion.
(NH4)3PO4
Ammonium
phosphate
Name the second ion.
Looks like a monster, but it’s really a pussycat.

55. ONE more example:
Cu2SO4
Name the first ion.
You should realize that you need a Roman Numeral since copper is a transition metal.
Copper I
sulfate
The Roman Numeral is the same as the charge.
What is the charge?
The charge of sulfate is -2.
Since there are two coppers, the charge of the copper must be +1.
Name the second ion.

56. Naming – you must use prefixes.
1 = mono 3 = tri = penta = hepta = nona
2 = di 4 = tetra 6 = hexa = octa = deca
Steps
The first nonmetal only gets a numeric prefix when there is more than one. No prefix if there is only one.
The second element always gets a numeric prefix and always has a suffix of -ide

57. Dinitrogen tetraoxide H2O Dihydrogen monoxide CCl4
CO2
Carbon dioxide CO
Carbon monoxide
N2O4
Dinitrogen tetraoxide
H2O
Dihydrogen monoxide
CCl4
Carbon tetrachloride
Name the first element. Since there is only one, no prefix is needed. The second element always gets a prefix and a suffix of –ide.
Name the first element. Since there are two present, the prefix “di” is needed. The second element always gets a prefix and a suffix of –ide.

58. AlCl3
What do you think about this one???
Be careful. This is a metal and nonmetal.
Always keep your Periodic Table in front of you for reference.
You may have been tempted to say “aluminum trichloride”. This is INCORRECT!
This is a binary IONIC compound. No prefixes are used. Simply aluminum chloride.
Given the names of binary molecular compounds, how do you write the formulas?
Very easy to do!!! The prefixes tell you how to write the formulas. DO NOT CONSIDER CHARGES. NONMETALS ARE ALL NEGATIVE SO TO USE CHARGES DOES NOT WORK!

59. SiO2 P2Cl5 Silicon dioxide Diphosphorous pentachloride
Silicon and oxygen are both nonmetals.
The lack of a prefix on silicon means that there is only ONE silicon.
The prefix “di” in front of oxide means that there are TWO oxygens.
SiO2
Diphosphorous pentachloride
P2Cl5
Phosphorous and chloride are both nonmetals.
The prefix “di” means that there are TWO phosphorouses (Is that a word?)
The prefix “penta” before chlorine means that there are five chlorines.

60. NO Is this not sooooooo easy!?? Nitrogen monoxide
Nitrogen and oxygen are both nonmetals.
The lack of a prefix on nitrogen means only ONE nitrogen.
The prefix “mono” on oxygen indicates ONE oxygen. NO
Is this not sooooooo easy!??

61. Let’s Practice
Ca(OH)2
Calcium hydroxide
SO2
Sulfur dioxide
(NH4)3PO4
Ammonium phosphate
Co2(CO3)3
Cobalt (III) carbonate
HBr
Hydrobromic acid
Ternary Ionic
Binary molecular
Ternary Ionic
Ternary Ionic
Binary acid

62. Potassium acetate KC2H3O2 Cadmium nitrate Cd(NO3)2 Aluminum oxide
Al2O3
Hydrosulfuric acid
H2S
Difluorine trioxide
F2O3
Ternary Ionic
Ternary Ionic
Binary Ionic
Binary acid
Binary molecular