1. Unit 3
Chapters 2 (p 64-66), 8,

2. Unit 2: Lectures 2 and 3 - Molecules, Ions, Nomenclature
Acids
H2SO4
H3PO4
HCl
Hydrogen-containing compounds
produce hydrogen ions (H+) when dissolved in water. They are molecular compounds that ionize in water. “aq” is short for aqueous which means water.
HCl(g)  H+(aq) + Cl-(aq)
or, more correctly, the hydronium ion (H3O+)
HCl(g) + H2O H3O+(aq) + Cl-(aq)
H2O
In general, acids are hydrogen containing compounds with a formula of HX, H2X, H3X, etc. where X can be an anion from Group 6A or 7A or X can be an oxyanion.

3. Acids hydrochloric acid HCl hydrobromic acid HBr hydroiodic acid HI
hypochlorous acid HClO
chlorous acid HClO2
chloric acid HClO3
perchloric acid HClO4
nitric acid HNO3
sulfuric acid H2SO4
phosphoric acid H3PO4

4. Unit 2: Lectures 2 and 3 - Molecules, Ions, Nomenclature
Acid Nomenclature
If the anion in the acid ends in -ide, change the ending to -ic acid and add the prefix hydro- .
HCl: hydrochloric acid
HBr: hydrobromic acid
HI: hydroiodic acid

5. Unit 2: Lectures 2 and 3 - Molecules, Ions, Nomenclature
Acid Nomenclature
If the anion in the acid ends in -ate, change the ending to -ic acid.
HClO3: chloric acid
HClO4: perchloric acid
H2SO4: sulfuric acid
H3PO4: phosphoric acid
HNO3: nitric acid

6. Unit 2: Lectures 2 and 3 - Molecules, Ions, Nomenclature
Acid Nomenclature
If the anion in the acid ends in -ite, change the ending to -ous acid.
HClO: hypochlorous acid
HClO2: chlorous acid
H2SO3: sulfurous acid

7. Unit 2: Lectures 2 and 3 - Molecules, Ions, Nomenclature
Names of Common Chemicals Containing Ions
common name or use
chemical name
formula
water
H2O
ammonia, window cleaner
ammonia
NH3(aq)
baking soda
sodium bicarbonate
NaHCO3
natural gas
methane
CH4
vinegar
acetic acid (5% solution)
CH3COOH
table salt
sodium chloride
NaCl
bleach
sodium hypochlorite
NaClO
muriatic acid
hydrochloric acid
HCl(aq)

8. Unit 2: Lectures 2 and 3 - Molecules, Ions, Nomenclature
Names of Common Chemicals
common name or use
chemical name
formula
hydrogen peroxide
H2O2
drinking alcohol
ethanol, ethyl alcohol
C2H5OH
rubbing alcohol
isopropyl alcohol, 2-propanol, isopropanol
CH3CH(OH)CH3
C3H7OH
nail polish remover
acetone
CH3COCH3
C3H6O
battery acid, oil of vitriol
sulfuric acid
H2SO4
lye, oven cleaner
sodium hydroxide
NaOH

9. Chemical Bonding and Molecular Geometry
Molecules (naming and writing formulas)
Lewis Symbols and the Octet Rule
Ionic Bonding
Covalent Bonding
Molecular Geometry

10. Chemical Bonds Three basic types of bonds Ionic
Electrostatic attraction between ions (cations-anions), transfer of electrons
Covalent
Sharing of electrons between non-metal atoms
Metallic
Metal atoms bonded to several other atoms by free moving electrons

11. Think about it! Salt (eg NaCl, KCl) vs. Sugar (C12O22H11)
solutions conduct solutions don’t electricity conduct electricity
electrolyte non-electrolyte
ionic molecular
Sugar and salt differ in the type of attractive forces between the atoms/ions in the compound.
Chemical bond: strong attractive force that exists between atoms (or ions) in a compound

12. H-O and Cl-Cl bonds result from sharing of electrons
Chemical Bonds
Covalent Bonds: the attractive force between atoms in a molecule that results from sharing of one or more pairs of electrons
non-metals
H2O : O
H H
Cl2 : Cl Cl
H-O and Cl-Cl bonds result from sharing of electrons

13. Molecules Chemistry happens among the electrons of atoms.
Bonds occur between atoms as a result of interactions among the electrons.
When the interaction results in shared electrons, the bond is said to be covalent and the entity formed is a molecule.
Formed from nonmetals.

14. Naming and writing formulas of binary molecular compounds
A molecular formula shows the number and type of elements in a molecule.
The molecular formula for water is H2O.
Molecule: non-metal elements only!
Proper chemical name includes individual element names.
Yes, there are RULES for naming!

15. Unit 2: Lectures 2 and 3 - Molecules, Ions, Nomenclature
Naming Binary Molecular Compounds
Name the element farther to the left on the periodic table. (Exception: O is written last unless it’s bonded to F.)
If both elements are in the same group, name the lower one first.
Give the anion name of the second element (ie replace the end of element name with “ide” ending, eg oxygen -> oxide, chlorine -> chloride).
Greek prefixes give the number of each atom in the formula.
mono- 1
di- 2
tri- 3
tetra- 4
penta- 5
hexa- 6
hepta- 7
octa- 8
nona- 9
deca- 10
mono- is not used on the first element listed CO
carbon monoxide
CO2
carbon dioxide
P4O10
tetraphosphorus decaoxide
N2O
dinitrogen monoxide

16. Nomenclature of Binary Compounds
Unit 2: Lectures 2 and 3 - Molecules, Ions, Nomenclature
Nomenclature of Binary Compounds
If the prefix ends with a or o and the name of the element begins with a vowel, the two successive vowels are often elided into one.
N2O5: dinitrogen pentoxide
pentaoxide

17. Name them!
Name the following compounds:
(a) SO2
(b) PCl5
(c) N2O3

18. Chemical bonds involves electrons, valence electrons
Electron configuration for sodium:
[Ne]3s1
The 3s electron of a sodium atom is a valence electron.
electrons residing in the incomplete outer shell of an atom
involved in chemical bonding and ion formation
For elements with atomic # <30, all outer shell electrons are valence electrons (those electrons beyond noble gas core!)

19. Lewis Symbols
Since valence electrons are involved in the formation of chemical bonds, it’s important to keep track of them.
Draw elements with valence electrons as dots:
electron-dot symbols or Lewis symbols
simple way to depict valence electrons and track them during the formation of chemical bonds

20. To write Lewis Symbols
You must be able to determine the number of valence electrons for the main group elements.
For main group elements: number of valence electrons for an element = group number of the element
e.g. N (group 5A) has 5 valence electrons
Br (group 7A) has 7 valence electrons

21. Lewis Symbols Lewis symbol has two components:
chemical symbol for the element
plus a dot for each valence electron
dots are placed on all 4 sides of the chemical symbol
all four sides of the symbol are equivalent
up to 2 dots (electrons) per side (start with single dot per side of square, then double up)

22. Lewis Symbol for Oxygen
Chemical symbol: O
Group number: 6A
# of valence electrons: 6 O

23. Draw the Lewis symbol for silicon.
Lewis Symbols
Draw the Lewis symbol for silicon.
Chemical symbol: Si
Group number: 4A
# of valence electrons: 4 Si

24. Draw the Lewis symbol for argon.
Lewis Symbols
Draw the Lewis symbol for argon.
Chemical symbol: Ar
Group number: 8A
# of valence electrons: 8 Ar

25. Octet Rule
The noble gases are particularly stable because their outer shell is full of electrons.
With the exception of He, all noble gases have 8 valence electrons.
ns2np6
Octet Rule: Atoms tend to gain, lose, or share electrons until they are surrounded by 8 valence electrons

26. Octet Rule
The octet rule can be used to predict the charge of ions formed by main group elements as well as the structure of molecular compounds.
BUT: There are many exceptions to the octet rule: H, He….

27. Covalent Bonding
Molecular compounds are held together by covalent bonds that result from the sharing of electrons.
Simplest example of a covalent bond is
H H
Indicates 2 shared electrons = 1 bond

28. Covalent Bonding
When 2 H atoms approach each other, electrostatic interactions occur between their respective electrons and their nuclei.
The two nuclei repel each other
The two electrons repel each other
The nuclei and the electrons attract each other.

29. Covalent Bonding
The attractions between the nuclei and the electrons cause the electron density to concentrate between the two nuclei.
The atoms in H2 are held
together by the electrostatic attraction of the two nuclei for the concentration of negative charge between them.
The shared pair of electrons between the two nuclei acts as “glue”.

30. Covalent Bonding
Lewis structures (also called electron-dot structures) can be used to represent the covalent bonds that are present in a molecule.
Symbol for each atom
Bond between atoms depicted using a solid line
Unshared electron pairs are shown around the appropriate atom

31. Lewis Structures
Lewis structures are representations of molecules showing all valence electrons, bonding and nonbonding.
NOTE: Octet of electrons around each Cl atom!

32. Covalent Bonding H + F H F = H F The formation of H2:
H H  H H or H H
The Lewis structure for HF:
H F H F = H F

33. Covalent Bonding
The bond between H and F in HF is called a single bond:
sharing of one pair of electrons
In some molecules, atoms attain an octet of electrons by sharing more than one pair of electrons.
Double bond
Triple bond

34. Covalent Bonding
Double bond: two electron pairs are shared between atoms
depicted using two lines to represent the two shared electron pairs
O C O or O C O
Carbon dioxide

35. Covalent Bonding
Triple bond: three electron pairs are shared between atoms
depicted using three lines to represent the 3 pairs of shared electrons
N N N N or N N
Nitrogen (N2)

36. Covalent Bonding
In some molecular compounds, the bonding electrons are shared equally between the atoms in the molecule:
H F N2
Nonpolar covalent bond: bonding electrons are shared equally

37. Covalent Bonding
In many molecular compounds, however, one atom attracts the bonding electrons more strongly than the other. d+ d-
Fluorine attracts electrons more strongly than hydrogen.
H – F
The fluorine end of the molecule has greater electron density than the hydrogen end. d+ d-
The H – F bond is a polar covalent bond.

38. Covalent Bonding Polar covalent bond:
a chemical bond in which the electrons are not shared equally
one atom attracts the bonding electrons more strongly
The polarity of a covalent bond can be determined using the difference in electronegativity between the two atoms.

39. Covalent Bonding Electronegativity:
The ability of an atom in a molecule to attract electrons to itself
Range: 0.7 (Cs) (F)
As electronegativity increases, the attraction that an atom has for electrons increases.

40. Covalent Bonding Trends to know: Electronegativity increases:
From left to right across a row
From bottom to top of a column
The four most electronegative elements are:
F (4.0)
O (3.5)
N (3.0)
Cl (3.0)

41. Covalent Bonding Chemicals bonds exist along a continuum:
The greater the difference in electronegativity between two atoms, the more polar their bond.
F – F D en = nonpolar covalent (en<0.5)
H – F D en = 1.9 polar covalent (0.5<en<2.0)
Li – F D en = 3.0 ionic (en>2.0)
Polar Covalent
Bonds
Nonpolar Covalent
Bonds
Ionic
Bonds

42. Testing Which of the following bonds is a polar covalent bond?
Br-Br C-H O-H Al-Cl
DEN=
0.45
1.34
1.55
Polar covalent (0.5< en < 2.0)

43. Polar Covalent Bonds H - F
When two atoms share electrons unequally, a bond dipole results.
Indicated by d+ and d- or
by an arrow pointing toward the more electronegative atom. d+ d-
H - F

44. Polar Covalent Bonds
The greater the difference in electronegativity, the more polar is the bond.