Chapter 07 and 08 Chemical Bonding and Molecular Structure.

Chapter 07 and 08Chemical Bonding

and MolecularStructure

Compound• Pure substance

• Made of 2 or more elements in a definite proportion by mass

• Physically and chemically different from the elements that make up the compound

• All elements (except Noble gases) react to gain a stable octet. (duet-for H through B)

• Compounds form to gain a stable valence shell which is LOWER IN ENERGY than the atoms before the reaction

Ionic compounds

• Metal gives all valence electrons to a nonmetal or semimetal.

• Both gain stable octets or duets.

• Ionic bond forms due to electrostatic attraction of cation(s) and anion(s)

• One unit is the lowest whole number ratio between the cation and anion. This unit is called a FORMULA UNIT

Covalent Compounds

• Formed when 2 or more nonmetals or a nonmetal and semimetal SHARE valence electrons in order to gain a stable octet.

• Tendency for atoms to obtain a stable octet is called the OCTET RULE.

Part 01Ionic

Bonding

1. Draw the electron dot (Lewis) Dot Diagram for the ionic compound formed between sodium and fluorine.

NaAtom

FAtom

d

Sodium must lose its one valence electron to get a stable octet.Fluorine must gain one electron to get a stable octet.The electron transfer is from sodium to fluorine and is always from metal to nonmetal.

[Na]Cation Anion

This is an ionic compound because it contains a metal cation and a nonmetal anion. Both ions have a stable octet.The stable octet is NEVER shown on the cation; it is ALWAYS shown on the anion.

1+ 1-

[ F ]d

This is a very stable compound. The positive and negative ions exerts a strong electrostatic attraction on each other and bond the ions together.

[Na]Cation Anion

1+ 1-

[ F ]d

The overall charge of the compound is zero because 1+ and 1- sums to zero. The overall charge must always be zero which shows that the number of electrons lost is equal to the number of electrons gained.

[Na]Cation Anion

1+ 1-

[ F ]d

Binary Ionic SaltBinary: Two ElementsIonic: Metal and NonmetalSalt: Metal and Nonmetal

Electron Dot or Lewis Dot Diagram

[Na]Cation Anion

1+ 1-

[ F ]d

FormulaShorthand method of representing a compound


Na F1+

1-

Metal on leftNonmetal on rightPositive on leftNegative on right

ALWAYS

[Na]Cation Anion

1+ 1-

[ F ]d

NameSodium Fluoride


Names of all binary compounds end in –ide.

[Na]Cation Anion

1+ 1-

[ F ]d

2. Draw the electron dot (Lewis) Dot Diagram for the ionic compound formed between calcium and chlorine.

Ca ClAtom Atom

Calcium must lose its TWO valence electrons to get a stable octet.Chlorine must gain one electron to get a stable octet.The electron transfer is from calcium to chlorine and is always from metal to nonmetal.

Ca Cl Cl This is an ionic compound because it contains a metal cation and a nonmetal anion. Both ions have a stable octet.The stable octet is NEVER shown on the cation; it is ALWAYS shown on the anion.

This is a very stable compound. The positive and negative ions exerts a strong electrostatic attraction on each other and bond the ions together.

1-

[Ca] [ Cl ] [ Cl ]2+1-

CationAnion Anion

The overall charge of the compound is zero because 2+ and 1- and 1- sums to zero. The overall charge must always be zero which shows that the number of electrons lost is equal to the number of electrons gained.

1-

[Ca] [ Cl ] [ Cl ]2+1-

CationAnion Anion

Binary Ionic SaltBinary: Two ElementsIonic: Metal and NonmetalSalt: Metal and Nonmetal


1-

[Ca] [ Cl ] [ Cl ]2+1-

CationAnion Anion

FormulaShorthand method of representing a compound

Ca Cl2+

1-

Metal on leftNonmetal on rightPositive on leftNegative on right

ALWAYS


2

1-

[Ca] [ Cl ] [ Cl ]2+1-

CationAnion Anion

3. Draw the electron dotdiagram for the ionic compound formed between potassium andoxygen.

KAtom

OAtom

d

Potassium must lose its one valenceelectron to get a stable octet.Oxygen must gain two electrons toget a stable octet.The electron transfer is frompotassium to oxygen.

K O d

This does not represent the formation of a compound. Oxygen does not havea stable octet because it has not gained two electrons.

A stable compound can form if a second potassium atom loses its one valence electron to the oxygen.

K O d

K

[K] [ O ]d

[K] 1+

1+ 2-

The name of the compound is potassium oxide. Its formula is K2

1+O2-.There are two electrons lostand two electrons gained.

4. Draw the electron dot diagram for the ionic compound formed between iron and bromine when iron has three valence electrons.

Fe Brd

Iron must lose its three valence electron to get a stable octet. Bromine can only gain one. The electron transfer is from iron to bromine.

Fe Br d

Br d

Br d

The three electrons are transferred from the iron to the brominewhen three bromine atoms are available.

[ Br ] [Fe]d

1- 3+

[ Br ] d

1-

[ Br ] d 1-

The name of the compound is iron(III) bromide. The Roman numeral is inserted after the name of the metal to indicate the number of electrons lost and the oxidation number. This is only done with elements that can change their oxidation numbers.

The formula of the compound is Fe3+Cl1-

3.

Rule: Transition metals and lead and tin can have variable oxidation numbers. Therefore a Roman numeral must be inserted into the name of the compound to indicate the number of electrons lost and the oxidation number of the metal. Exceptions Ag is always 1+, Cd and Zn are 2+

What is the formula for:Calcium Fluoride Ca

2+F

1-

2

Aluminum oxide Al3+ O 2-2 3

Tungsten(IV) Sulfide W4+

S2-

2

Sodium Carbide Na1+

C4-

4

Go to page 73 in notes

What is the name of: 42

2 CMg Magnesium Carbide

3ScF Scandium (III) Fluoride

OAg2 Silver Oxide NO ROMAN numeral!

2SnS Tin (IV) Sulfide

FrH Francium Hydride

Assignment: p 74-76 (notes)

Chapter 07 and 08 Chemical Bonding and Molecular Structure.

Documents