Three Types of Bonding

(1) Metallic

(2) Ionic

(3) Covalent

Sea of electrons model used to explain bonding between metal atoms; it is also useful in explaining characteristics of metals (they conduct heat and electricity, are maleable, are ductile, etc.)

The valence electrons of metal atoms can be modeled as a sea of electrons.

The model involves a positively charged kernel (nucleus and nonvalence electrons) and valence electrons that are free to move or drift freely from one part of the metal to another. In this model the valence electrons are mobile.

Metallic bonds consist of the attraction of the free-floating valence electrons for the positively charged kernel of the metal atom

Metallic Bonding

Formation of Ionic Compounds

•Formation of Ionic Compounds

–What is the electrical charge of an ionic compound?

• Compounds composed of cations and anions are called ionic compounds.•

7.2

Formation of Ionic Compounds

•Formation of Ionic Compounds

–What is the electrical charge of an ionic compound?

• Compounds composed of cations and anions are called ionic compounds.• Although they are composed of ions, ionic compounds are electrically neutral.

7.2

Formation of Ionic Compounds

• Aluminum metal and the nonmetal bromine react to form an ionic solid, aluminum bromide.

7.2

Formation of Ionic Compounds

• NaCl is the chemical formula for sodium chloride.

7.2

Properties of Ionic Compounds

–Most ionic compounds are crystalline solids at room temperature. –Ionic compounds generally have high melting points.

–Other points to Know?

–Ionic compounds can conduct an electric current when melted or dissolved in water…….

7.2

Molecules and Molecular Compounds• In nature, matter takes many forms.

The noble gases, including helium and neon, are monatomic. That means they exist as single atoms. • Represented by symbols: He, Ne, etc)• the noble gases are not molecules

8.1

Molecules and Molecular CompoundsSome elements do exist as diatomic molecules.

Hydrogen H2 (g)

Oxygen O2 (g)

Fluorine F2 (g)

Bromine Br2 (l)

Iodine I2 (s)

Nitrogen N2 (g)

Chlorine Cl2 (g)

8.1

(note these are molecules but they are not compounds)

A molecule is a neutral group of atoms joined together by covalent bonds. Air contains oxygen molecules.

A diatomic molecule is a molecule consisting of two atoms. An oxygen molecule is a diatomic molecule.

Molecular Formulas8.1

Molecular Formulas• Formulas of Some Molecular Compounds

8.1

Bond Polarity and Polarity of Molecules

• Bond Polarity can be predicted by differences in Electronegativity (Use table S)

• Molecules with Polar Bonds may be either polar or nonpolar

• Use SNAP to predict molecule polarity

• Examples CH4, CO2, H2, are all nonpolar molecules

• (H2O, HCl, NH3 are all polar molecules

Metallic Bonding

(ch 7)

BONDING

•Sea of electrons model used to explain bonding in metals•Kernel & delocalized mobile valence electrons

Metallic Bonding

(ch 7)

Ionic Bonding

(ch 7)BONDING

Electrostatic attraction of negatively and positively charged ions

Can be formed as a result of the transfer of electrons between metal and nonmetal atoms to form cations and anions

Metallic Bonding

(ch 7)

Ionic Bonding (ch

7)

Covalent Bonding (ch

8)

• Electrons are shared between atoms

• Covalent bonds may be nonpolar (equal sharing of electrons) or polar (unequal sharing of electrons )

BONDING

8.2

The Octet Rule in Covalent Bonding

•The Octet Rule in Covalent Bonding

–In covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases. –Covalent bonds may be single (as in a F2 molecule), or double (as in an O2 molecule) or triple (as in a N2 molecule)

Single Covalent Bonds• The hydrogen and oxygen atoms attain noble-gas

configurations by sharing electrons. The oxygen has 2 unshared pairs of electrons.

8.2

Single Covalent Bonds• The ammonia molecule has one unshared pair of

electrons.

8.2

Single Covalent Bonds

• Methane has no unshared pairs of electrons.

8.2

8.2Double and Triple Covalent BondsA bond that involves two shared pairs of electrons is

a double covalent bond. (ex: O2 has a double covalent bond between the two oxygen atoms and each oxygen atom has two unshared pair of electrons.)

A bond formed by sharing three pairs of electrons is a triple covalent bond. (ex. N2 has a triple covalent bond between the two nitrogen atoms and each nitrogen has one pair of unshared electrons)

8.2

Double and Triple Covalent Bonds

• Carbon dioxide gas is soluble in water and is used to carbonate many beverages. A carbon dioxide molecule has two carbon-oxygen double bonds.

Coordinate Covalent Bonds

• A polyatomic ion, such as NH4+ or H3O+ , is a tightly

bound group of atoms that has a positive or negative charge and behaves as a unit. One of its bonds is a coordinate covalent bond.

8.2

Metallic Bonding

(ch 7)

Ionic Bonding (ch

7)

Covalent Bonding (ch

8)

Bonding in:NaCl ?HCl ? H2O ?

Bonding in ionic compounds containing polyatomic ions:Na2CO3 ?BaSO4 ? NH4Cl ?

Polyatomic Ions

•Polyatomic Ions– What are the two endings of the names of most

polyatomic ions? – (Hint: use Table E)

9.1

Polyatomic Ions• These models show the structures of four common

polyatomic ions.

9.1

Polyatomic Ions• Sodium hydrogen carbonate can relieve an upset

stomach.

• What is its chemical formula?• (Hint: Use table E)

9.1

• Carbon and oxygen combine to form carbon monoxide (CO) and carbon dioxide (CO2), but these two invisible gases are very different.

9.3 Naming Binary Molecular Compounds

•A prefix in the name of a binary molecular compound tells how many atoms of an element are present in each molecule of the compound.

9.3

Naming Binary Molecular Compounds

You MUST know these Prefixes

• Name the elements in the order listed in the formula.

• Use prefixes to indicate the number of each kind of atom.

• Omit the prefix mono- when the formula contains only one atom of the first element in the name.

• The suffix of the name of the second element is -ide.

9.3 Naming Binary Molecular Compounds

Practice

• What are the names of the following molecular compounds?

CS2

BCl3

IF7

PCl5

Practice

• What are the names of the following molecular compounds?

CS2 carbon disulfide

BCl3 boron trichloride

IF7 iodine heptafluoride

PCl5 phosphorus pentachloride