Covalent Bonds and Molecular
Geometry
 Name and Formulas
 Binary Molecular Compounds
 Acids
 Lewis Symbols and Lewis Structures
 Geometries:
 Electron Domain
 Molecular
 Polarity
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.
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
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.
H
O
H
H
H C H
H

H H
H C C O H
H H
Molecular compounds usually contain nonmetals only.
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.
Naming Binary Molecular Compounds
Prefix
mono
di
tri
tetra
penta
hexa
hepta
octa
nona
deca
Meaning
1
2
3
4
5
6
7
8
9
10

You must know the
prefixes for one
through ten.
P4S10
Tetraphosphorus decasulfide
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
Naming Binary Molecular Compounds
Example: Name the following binary molecular
compounds.
N2O4
PCl5
Cl2O7
SO3
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
Formulas for Binary Molecular Compounds
Example: Write the correct formula for each of
the following compounds.
Dinitrogen monoxide
Phosphorus pentachloride
Xenon hexafluoride
Disulfur dichloride
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
O
or
 Their formula contains COOH, CO2H or C OH
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)
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
Oxyacids

Naming acids derived from oxyanions of S or
P:
 H2SO4 :
 oxyanion = sulfate
 Sulfic acid
Sulfuric acid
 H3PO4 :


oxyanion = phosphate
Phosphic acid
Phosphoric acid
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)
HBr (g)
hydrogen sulfide
hydrogen bromide
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
Naming Acids
Example: Write the correct name for the
following acids.
HCl (aq)
HC2H3O2
HCN (g)
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.
Formulas for Acids
Example: Write the formula for:
Carbonic acid
Hydrogen sulfide
Acetic acid
Hydrochloric acid
Naming Acids

You must know the names and formulas for
the following acids:
HF (aq)
HCl (aq)
HBr (aq)
HI (aq)
HClO4
HClO3
H2SO4
HNO3
hydrofluoric acid
hydrochloric acid
hydrobromic acid
hydroiodic acid
perchloric acid
chloric acid
sulfuric acid
nitric acid
Naming Acids

You must know the names and formulas for
the following acids:
H3PO4
HC2H3O2
H2CO3
H2S (g)
HCN (g)
HF (g)
HCl (g)
HBr (g)
HI (g)
phosphoric acid
acetic acid
carbonic acid
hydrogen sulfide
hydrogen cyanide
hydrogen fluoride
hydrogen chloride
hydrogen bromide
hydrogen iodide
Naming - Revisited
Example: Write the correct formula for each of
the following.
Calcium nitrate
Dinitrogen trioxide
Phosphoric acid
Aluminum hydroxide
Hydrogen sulfide
Naming – Revisited

Before you can correctly name a compound or
write its formula, YOU MUST determine which
type of compound it is:
 Ionic
 Acid
 Binary
Molecular

starts with a metal or NH4
starts with H or Hn
two non-metals
THEN use the appropriate naming system or
method to write the formula.