Covalent Bonds and Molecular Geometry Name and Formulas

Binary Molecular CompoundsAcids

Lewis Symbols and Lewis Structures Geometries:

Electron DomainMolecular

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.

Molecular compounds usually contain non-metals only.

HO

H C

H

H H

H

C

H

H

H

C

H

H

O H

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

You must know the prefixes for one through ten.

P4S10

Tetraphosphorus decasulfide

PrefixMeaningmono 1di 2tri 3tetra 4penta 5hexa 6hepta 7octa 8nona 9deca 10

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 CompoundsExample: 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

pentoxideP2O5

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

or Their formula contains COOH, CO2H or

O

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) hydrogen sulfideHBr (g) 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 AcidsExample: 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 AcidsExample: 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) hydrofluoric acidHCl (aq) hydrochloric acidHBr (aq) hydrobromic acidHI (aq) hydroiodic acidHClO4 perchloric acidHClO3 chloric acidH2SO4 sulfuric acidHNO3 nitric acid

Naming Acids You must know the names and formulas

for the following acids:

H3PO4 phosphoric acidHC2H3O2 acetic acidH2CO3 carbonic acidH2S (g) hydrogen sulfideHCN (g) hydrogen cyanideHF (g) hydrogen fluoride HCl (g) hydrogen chloride HBr (g) hydrogen bromideHI (g) hydrogen iodide

Naming - RevisitedExample: 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 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.