1. Covalent Bonds and Molecular Geometry
Name and Formulas
Binary Molecular Compounds
Acids
Lewis Symbols and Lewis Structures
Geometries:
Electron Domain
Molecular
Polarity

2. Compounds
Compounds form when the valence electrons present in the atoms of two or more different elements interact.
If electrons are transferred from one element to another, ions are formed, and an ionic compound results.
If electrons are shared between two or more atoms, then a covalent bond forms, and a molecular compound results.

3. Compounds
Ionic compounds are composed of ions that are held together by ionic bonds.
Electrostatic force of attraction between oppositely charged particles.
Ionic compounds often contain a metal and one or more nonmetals.
NaCl
Al2(CO3)3
Compounds containing the ammonium ion are also ionic!
(NH4)2SO4

4. Molecular Compounds
Molecular compounds are composed of atoms that are held together by covalent bonds.
The attractive force between two atoms that results from sharing electrons
Each pair of shared electrons is represented by a single straight line.
Molecular compounds usually contain non-metals only.

5. Naming Binary Molecular Compounds
Binary molecular compounds are composed of molecules containing two non-metals that share electrons.
The names of binary molecular compounds give both the number and type of each atom present.
Prefix element name prefix element name with “ide” ending
Greek prefixes are used to indicate the number of each atom present in a molecule of the compound.

6. Naming Binary Molecular Compounds
Prefix Meaning
mono 1
di 2
tri 3
tetra 4
penta 5
hexa 6
hepta 7
octa 8
nona 9
deca 10
You must know the prefixes for one through ten.
P4S10
Tetraphosphorus decasulfide

7. Naming Binary Molecular Compounds
Special conventions for using Greek prefixes:
Mono is never used with the first element (but it’s always used if only one atom of the second element is present)
The ending “a” or “o” in a prefix is dropped if the name of the element begins with a vowel.
CO:
Not monocarbon monooxide
carbon monoxide

8. Naming Binary Molecular Compounds
Example: Name the following binary molecular compounds.
N2O4
PCl5
Cl2O7
SO3

9. Formulas for Binary Molecular Compounds
To write the formula for a binary molecular compound:
Write the elemental symbol of the first atom listed in the name.
Use the numerical value of the prefix in front of that element as the subscript.
Write the elemental symbol for the second element present.
Use the prefix in front of the “ide” element as the subscript for the second element.
Diphosphorus pentoxide
P2O5

10. Formulas for Binary Molecular Compounds
Example: Write the correct formula for each of the following compounds.
Dinitrogen monoxide
Phosphorus pentachloride
Xenon hexafluoride
Disulfur dichloride

11. Acids
Acids are molecular compounds that form hydrogen ions (H+) when dissolved in water.
HCl (aq)
H2S (g)
H3PO4 (aq)
Acids can be recognized because:
Their formula starts with Hn or
Their formula contains COOH, CO2H or

12. Naming Acids The name of an acid depends on the type of acid:
Acids with oxygen (oxyacids)
Acids without oxygen
Gases (pure)
Aqueous solutions (dissolved in water)

13. Oxyacids Oxyacids are acids that contain oxygen.
If the acid contains oxygen,
Write the name of the anion
Change anion ending from “ate” to “ic acid” OR
Change anion ending from “ite” to “ous acid”
HNO3 nitrate  nitric acid
HNO2 nitrite  nitrous acid

14. Oxyacids Naming acids derived from oxyanions of S or P: H2SO4 :
oxyanion = sulfate
Sulfic acid Sulfuric acid
H3PO4 :
oxyanion = phosphate
Phosphic acid Phosphoric acid

15. Acids w/o Oxygen – Pure (Gases)
If the acid does not contain oxygen and is a gas (g):
Name the acid as if it was an ionic compound:
Start with “hydrogen”
Do not use a prefix to indicate how many hydrogen atoms are present!
Add the name of the anion
H2S (g) hydrogen sulfide
HBr (g) hydrogen bromide

16. Acids w/o Oxygen – Dissolved in H2O
If the acid does not contain oxygen and is dissolved in water (aq):
Start with hydro
Add the name of the anion
Change “ide” to “ic acid”
HBr (aq) hydrobromic acid
HI (aq) hydroiodic acid

17. Naming Acids Example: Write the correct name for the following acids.
HCl (aq)
HC2H3O2
HCN (g)

18. Formulas for Acids
Given the name of an acid, you should be able to write its formula:
First decide which category of acid it is:
No oxygen, (aq) (begins with “hydro”)
No oxygen, (g) (begins with “hydrogen”)
Oxyacid
Write the formula for the anion (including charge).
Add enough H+ ions to make a neutral compound.
Add (g) or (aq) if appropriate.

19. Formulas for Acids Example: Write the formula for: Carbonic acid
Hydrogen sulfide
Acetic acid
Hydrochloric acid

20. Naming Acids
You must know the names and formulas for the following acids:
HF (aq) hydrofluoric acid
HCl (aq) hydrochloric acid
HBr (aq) hydrobromic acid
HI (aq) hydroiodic acid
HClO4 perchloric acid
HClO3 chloric acid
H2SO4 sulfuric acid
HNO3 nitric acid

21. Naming Acids
You must know the names and formulas for the following acids:
H3PO4 phosphoric acid
HC2H3O2 acetic acid
H2CO3 carbonic acid
H2S (g) hydrogen sulfide
HCN (g) hydrogen cyanide
HF (g) hydrogen fluoride
HCl (g) hydrogen chloride
HBr (g) hydrogen bromide
HI (g) hydrogen iodide

22. Naming - Revisited
Example: Write the correct formula for each of the following.
Calcium nitrate
Dinitrogen trioxide
Phosphoric acid
Aluminum hydroxide
Hydrogen sulfide

23. Naming – Revisited
Before you can correctly name a compound or write its formula, YOU MUST determine which type of compound it is:
Ionic starts with a metal or NH4
Acid starts with H or Hn
Binary
Molecular two non-metals
THEN use the appropriate naming system or method to write the formula.