1. Chemical Bonding
Chapter 13

2. Ions and Chemical Bonds

3. Bonding When atoms combine they form a chemical bond
The force of attraction between two or more atoms.

4. Valence Electrons Are the outer most electrons of an atom.
They play a huge role in how an atom bonds.

6. 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 :
       

7. Lewis Structure
Is a diagram of atoms that only shows the valance electrons
Ex:
Cl Na H Ar

8. Li Be Al C N S Br Kr Check Understanding
Determine the number of valance electrons in each of the following atoms:
Li Be Al C
N S Br Kr

10. The Octet Rule
The octet rule says that atoms tend to gain, lose or share electrons so they can have eight electrons in their outer shell.
They do this because they are more stable with a complete outer shell.
There are some situations where it does not apply. For example, hydrogen wants to take one on to complete its outer shell with 2 electrons.

11. Oxidation Numbers
Oxidation numbers represent the charges that an ion has when it gains or loses its valence electrons.
They are listed as a + or – above each column on the periodic table.

12. Ion
An ion is an atom which has lost or gained one or more electrons, making it positively or negatively charged.
A negatively-charged ion, gains an electrons so it has more electrons then it has protons.
A positively-charged ion, looses electrons so it has more protons then electrons.
A polyatomic ion is an ion that is made up of more than one atom.
Poly= Many Atomic= Atoms
Ex: NH4+ is the chemical formula for an ammonium ion. It contains two elements nitrogen and hydrogen and has a positive charge.

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

15. Ionic Bonds
Bonds that form as a result of the attraction between positive and negative ions. The atoms are attracted to each other because of their opposite charges
We call the compound that results from the bond an Ionic Compound.
They usually form between a metal and a nonmetal

16. F K In an IONIC bond, electrons are lost or gained,
resulting in the formation of IONS
in ionic compounds. F K

17. K F

18. K F

19. K F

20. K F

21. K F

22. K F _ + The compound potassium fluoride
consists of potassium (K+) ions
and fluoride (F-) ions

23. K F _ + The ionic bond is the attraction between the positive K+ ion
and the negative F- ion

25. Formulas
Reminder: A chemical formula is the combination of symbols that show the elements in the compound. i.e. MgCl2
If a molecule contains more than one atom of a particular element, you indicate it by using a subscript after the chemical symbol (ex: the 2 in MgCl2).
It tells you the ratio of atoms in the compound (MgCl2 has a 1 to 2 ratio).
If no subscript is written the number 1 is understood( NaCl there is a 1 to 1 ratio).
A coefficient acts as a multiplier for all of the atoms in the entire compound, it is found in front of the chemical formula
Ex: the 5 in 5 MgCl2

26. Example
MgCl2
Here we have one molecule of magnesium chloride.  The subscript 2 in the formula above
only pertains to the chlorine in the compound.  
The total number of atoms in the compound is 3.
Now let us put a coefficient in front of the molecule and see how that changes things.
5 MgCl2
The coefficient 5 refers to the entire molecule.   It shows that there are 5 compounds of
magnesium chloride.
Since each molecule is made up of 3 atoms, the total number of atoms is now 15.  There are
5 magnesium atoms and 10 chlorine atoms.
How many atoms are in the following bond 3Na2S
Sodium(Na)____
Sulfur(S)____
Sodium Sulfide(3Na2S) ____ = total atoms 6 3 9

27. Naming Ionic Compounds
The name of the positive ion comes first, followed by the name of the negative ion.
The metal will be the positive because it gives away electrons and the nonmetal will be the negative because it gains electrons.
If the negative ion is a single element the end of its name changes to –ide.
Ex: NaCl- Sodium Chloride MgO- Magnesium Oxide
If the negative ion is polyatomic, its name usually ends in –ate or – ite.
Ex: NH4NO3- Ammonium nitrate
What is the name of the ionic compound with the formula K2S? ______________
Potassium Sulfide

28. Properties of Ionic Compounds
Hard
Brittle
Crystals
High melting points- NaCl melts at 801˚C= ˚F
When dissolved in water they are electrolytes.
An electrolyte solution is one that can conduct electricity.
Ionic bonds in solid form are poor conductors.

29. Covalent Bonds
The chemical bond formed when two atoms share electrons.
Usually form between nonmetal + nonmetal.
We call the neutral group of atoms joined by a covalent bond a molecule.

30. In covalent bonding,
atoms still want to follow the
octet rule and have a complete valance shell

31. But rather than losing or gaining
In covalent bonding,
atoms still want to follow the
octet rule and have a complete valance shell
But rather than losing or gaining
electrons, atoms now share an electron pair.

32. The shared electron pair is called a bonding pair
In covalent bonding,
atoms still want to follow the
octet rule and have a complete valance shell
But rather than losing or gaining
electrons, atoms now share an electron pair.
The shared electron pair
is called a bonding pair

33. Chlorine
forms a
covalent
bond
with
itself
Cl2

34. How
will
two
chlorine
atoms
react? Cl Cl

35. Cl Cl Each chlorine atom wants to gain one electron to achieve
a full outer shell.

36. Cl Cl do to achieve an octet? What’s the solution – what can they
Neither atom will give up an electron.
What’s the solution – what can they
do to achieve an octet?

37. Cl Cl

38. Cl Cl Cl Cl

39. Cl Cl

40. Cl Cl

41. Cl Cl
complete

42. Cl Cl
complete

43. Cl Cl The complete outer shell is achieved by each atom sharing the
electron pair in the middle

44. Cl Cl The complete outer shell is achieved by each atom sharing the
electron pair in the middle

45. Cl Cl
This is the bonding pair

46. Cl Cl
It is called a SINGLE BOND

47. Single bonds are abbreviatedCl Cl
Single bonds are abbreviated
with a dash

48. This is the chlorine molecule,Cl Cl
This is the chlorine molecule,
Cl2

49. O2
Oxygen is also one of the diatomic molecules

50. O
How will two oxygen atoms bond?

51. O
Each atom has two unpaired electrons

52. O
Oxygen atoms want to gain two electrons.

53. Both electron pairs are shared.

54. O O
6 valence electrons
plus 2 shared electrons
= full valance shell

55. O O
6 valence electrons
plus 2 shared electrons
= full valance shell

56. O O
two bonding pairs,
making a double bond

57. O O =
For convenience, the double bond
can be shown as two dashes.

58. This is the oxygen molecule,=
This is the oxygen molecule, O2

59. Molecular Compounds A covalent bond is called a molecule.
Ex: CH4 Methane H2O is Water
Properties:
Low melting and boiling points
Poor conductors

60. Polar Bonds
A covalent bond in which electrons are shared unequally is called a polar bond. ex: water molecules
One atom pulls more strongly on a shared electron causing a slight charge.
Polar molecules tend to pull close together because the negative end of each molecule is attracted to the positive end of other molecules.

61. Nonpolar Bonds
If the electrons are shared equally it is called a nonpolar bond.
A molecule may contain a polar bond and still be nonpolar overall. In order for this to happen the molecule must bond in a straight line with opposite pulling. Ex: carbon dioxide
There is little attraction between non polar molecules

62. Why Doesn’t Oil & Water Mix?
The molecule in vegetable oil are nonpolar and have little attraction to other molecule.
Water molecules are polar and are strongly attracted to one another.
SO, the water stays with the water which leave the oil by itself.
Adding soap allows them to mix easily because the soap molecule contains one end that is an ionic bond and the other end is a nonpolar covalent bond.
The nonpolar end mixes with the oil and the charge
on the ionic end attracts the water

63. Metallic Bonds
An attraction between a positive metal ion and the electrons surrounding it.
In other words:
Many electrons are shared by many atoms.
A metal consists of positively charged metal ions embedded in a “sea” of valence electrons.

64. Metallic Properties
The “sea of electrons” model of solid metals explains their properties:
Heat/electrical conductivity
The free moving valance electrons make it easier for the particles to move faster.
Changes in shape
Ductile
Malleable
This happens because the ions in the metal are not attracted to each other, instead they are attracted to the loose electrons all around them.
Luster
A metals luster is due to its valance electrons. They absorb and then reflect the light which we see as shiny.