MondayNovember 7, 2011

(Covalent Bonding; Naming Covalent

Compounds)

Bell RingerMonday, 11-7-11

Using your Periodic Table and your ion charts, name these chemical

compounds:HNO3AlBr3

HF

H2SO4

HCl CaCl2

H3PO4

GaI3

Assignment Currently Open

Summative or

Formative

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WS - Valence Electrons and Electron Configuration F 10/13 10/19

Lab – The Flame Test F 10/14 10/17 11/3 11/7

Quiz – The Organization of the Electron Cloud S 10/21 10/21 10/26 11/9

WS – Chemical Bonding F 10/21 10/27

Quiz – Chemical Bonding and Bonding Character S 10/25 10/25 10/28 11/11

Activity - Ionic Properties vs. Covalent Properties F 10/26 10/28 11/3 11/7

Quiz – Ionic vs. Covalent Bonding and Properties S 10/28 10/28 10/31 11/14

AnnouncementsI will not be available today after school.

SaltsA salt is an ionic

compound composed of a cation from a base and the anion from an acid.

For example, table salt (NaCl) contains the

anion from hydrochloric acid (HCl) and the cation

from the base sodium hydroxide (NaOH.)

HCl NaOH+ - + -

Salts are named in the same way as other ionic compounds.

Covalent BondingIt’s

nice to share!

Covalent Bondingand Molecular Compounds

A molecule is a neutral group of atoms that are

held together by covalent bonds.

A molecule may consist of two or more atoms of

the same element, or two or more different

types of atoms.A molecular compound is a chemical compound

whose simplest units are molecules.

A chemical formula indicates the relative numbers of atoms

of each kind in a chemical compound by using atomic

symbols and numerical subscripts.

A molecular formula shows the types and numbers of atoms

combined in a single molecule of a molecular compound.A diatomic molecule is a

molecule containing only two atoms.

Covalent Bondingand Molecular Compounds

H2O NaCl

CO2

O2

Formation of a Covalent BondAs atoms approach each other, their charged particles begin to interact.

Nuclei and clouds attract each other - potential energy decreases.

The two nuclei and the two e- clouds repel each other

– potential energy increases.

At a given distance, the repulsion equals the attraction, energy

potential is at its lowest, and the bond forms.

Characteristics of a Covalent BondBond length is the distance between two bonded atoms at their minimum potential energy, that is, the average distance between two bonded atoms.

Example) The bond length of H-H is 75 pm.At this length, the one electron of each atom is

shared by both atoms.

Characteristics of a Covalent Bond

Bond energy is the energy required to break a chemical bond and form neutral,

isolated atoms.Example) The bond energy to break H2 is

436 kJ.Sharing electrons allows each atom to

experience the effect of the stable electron configuration of a Noble Gas.

Keep in mind that bond lengths and bond energies vary with the types of atoms that

have bonded.

Bond Length and Bond Energy

Multiple Covalent BondsA covalent bond produced by

the sharing of two pairs of electrons between two atoms is

called a double bond.

Multiple Covalent BondsA covalent bond produced by the sharing of three pairs of

electrons between two atoms is called a triple bond.

Multiple Covalent BondsDouble and triple bonds

are referred to as multiple bonds.

Multiple Covalent BondsSample Problem

Draw the Lewis structure of methanal (formaldehyde)

CH2O

Chemical FormulasFor a molecular compound, the chemical formula revels the type and number of atoms of each element contained in a

single molecule of the compound.

Naming Binary Molecular Compounds

• Molecular compounds are composed of individual covalently bonded units, or molecules.

• The prefix system is an older nomenclature for naming molecular compounds.

• A Greek prefix is used in front of substance names in the compound to indicate the number of units of that substance that are present.

PracticeName the following covalent

compounds:CO2

Write the chemical formulas for the following covalent compounds:

dinitrogen trioxide

H2O CCl4carbon dioxide

dihydrogen monoxide

carbon tetrachlorid

e

tetraphosphorus decaoxide

N2O3 P4O10

1. The less-electronegative element is given first and is given a prefix only if it contributes more than one atom to a molecule of the compound.

2. The second element is named by combining a prefix indicating the number of atoms contributed by the element, the root of the name of the second element, and the ending –ide, which usually indicates that a compound contains only two elements.

3. The o or a at the end of a prefix is usually dropped when the word following the prefix begins with another vowel – for example, monoxide or pentoxide.

Naming Binary Molecular Compounds

Naming Binary Molecular Compounds

In general, the order of nonmetals in

compound names and formulas is:

C, P, N, H, S, I, Br, Cl, O, F

Naming Binary Molecular Compounds

Examples

– What is the name of As2O5?

– Diarsenic pentoxide

– Write the formula for oxygen difluoride

– OF2

Naming Binary Molecular Compounds