Ch 6.1 Chemical Bonding

Chemical Bonds

– the attractive forces that hold different atoms or ions together

(Intramolecular or electrostatic Forces

Why Bond?

Atoms bond to achieve a full outer energy level

OCTET RULE: They want 2/8 VALENCE electrons.

Few exceptions

Ex. BF3 and SF6

I guess not everyone can hold 8 e-

Bond Structures

Ionic Crystal or formula Units (strongest Bond)

Network Structures (Strong Covalent solids)

Molecular (most common covalent bond, weakest)

Chemical Bonds: Types

COVALENT METALIC IONIC

ALL NONMETALS atomsHolding a compound or

element togetherALL METALS

holding an elementtogether

METAL and NONMETAL ionsHolding a compound

together

Ch. 6.4 Metallic bond

Formed by the attraction between positively charged metal ions and the “sea of electrons” around them.

Held together by delocalized, free-flowing electrons along the bond

Holds metal elements and alloys together

Metallic bond Properties

Strong Bonds

Malleable

High melting points

Ductile

Good conductors of electricity

Ch 6.1 Electronegativity Difference (END)

the difference in electronegativity between two atoms in a bond.

Bonds are rarely ionic or covalent.

Electronegativity Difference (ED)

EX. NO N=3.0 O=3.4

[3.4-3.0] = 0.4

Electronegativity difference of NO = 0.4

Tells us two things

Bond Properties and Polarity

If ED is > 1.7, then the compound has more polar ionic properties. (strongest)

If ED is < 1.7, then the compound has more polar covalent properties

If the ED is < 0.3, then the compound is nonpolar covalent. (weakest)

Polarity (ch. 6.1, 6.5)

Property of a molecule’s bond caused by an unsymmetrical charge distribution

Polar molecules are unsymmetrical in shape

Nonpolar molecules are symmetrical in shape

It is important to note that nonpolar molecules can have polar bonds

Polar Covalent Molecules

The atom with the higher electronegativity will attract the electrons more strongly.

This will cause partial charges to develop on each side of the molecule (ع +ع-)

Contain Dipole forces

Unequal Sharing

Unsymmetrical ShapePolar molecule

Unequal Sharing

Nonpolar Covalent Molecules

Molecules where the atoms have similar electronegativity's

This will cause partial charges cancel

Equal sharing

Held by weaker London dispersion forces

Boron Trihydride+

+

+

Symmetrical shape

Nonpolar molecule

Same all around

BPolar bond

Equal Sharing

Using Dot Diagrams

Dot diagrams may be used to show how electrons are shared or how they will be transferred

Ch 6.2 Covalent Bonds

A bond formed by the sharing of valence electrons (co – VALENT)

Also called molecules

Formed between two or more nonmetal atoms

TYPES OF BONDS

SINGLE BONDS

DOUBLE BONDS

TRIPLE BONDS

Molecular bond Properties (<1.7)

Weak bonds (molecules)

The longer the bond the less bond energy needed to break bond

Molecular compounds have low melting points and are bad conductors of electricity (no ions)

Can be solids, liquid or gas phase at room temp.

Dot Diagrams and Structural Formulas

VSEPR and Molecular Geometry

Ch. 7.1Molecular Formula

The actual formula of a covalent molecule.

Empirical Formula

The simplest whole-number ratio a

chemical formula can have.

Different covalent compounds can

have the same empirical formula

Ionic formulas are always empirical

Organic Molecules

Naming Covalent Compounds Prefixes for # of atoms

Mono – 1

Di - 2

Tri - 3

Tetra - 4

Penta - 5

Hexa – 6

Hepta - 7

Octa - 8

Nona - 9

Deca - 10

Naming Covalent Compounds

Step 1

Identify the number of atoms in the first element

Ex. H2O two H atoms

Naming Covalent Compounds

Step 2

Identify the number of atoms in the 2nd element.

Ex. H2O one O atom

Naming Covalent Compounds

Step 3

Name the compound with the appropriate prefixes. Ex. H2Odihydrogen monoxygen

Naming Covalent Compounds

Step 4 add an -ide ending to the second element

Ex.Dihydrogen monoxide

Ionic bond (ch. 6.3)

A bond formed by the attraction between oppositely charge ions.

The transferring of valence electrons

Each ion will have 2/8 valence electrons

Formed between metal ions and nonmetal ions

Na+ + Cl- NaCl

Ionic bond Properties (>1.6)

Very Strong bonds (formula units)

Compounds made up of ionic bonds have high melting points and are good conductors of electricity when dissolved or melted (ions free to move)

solid phase (salts)

Ch. 7.1 Writing Ionic formulas

Step 1 Calcium Fluoride

Write both positive and negative ions (use ion table if you need it)

Ca2+ F-1

Writing Ionic Compounds

Step 2

Criss-cross numbers down, making subscripts

Ca2+ F-1

Ca1 F2

Writing Ionic Compounds

Step 3Combine your new compound.

Ca1 F2 Ca1F2

Ionic bonds

Ionic bonds may contain polyatomic ions in them.

An ion made from two or more atoms covalently bonded together that act like a single ion.

A molecule with a charge, example sulfate (SO4)-2

EX Na+1 + (SO4)-2 → Na2(SO4)

Covalent Bond Ionic bond between 2 ions

Polyatomic ion

Aluminum Carbonate

Al+3 (CO3)-2

Al2 (CO3)3

Al2(CO3)3

Ch. 7.1

Naming Ionic Compounds

Step one – Name the first ion in the formula

Ex. CaCl2 – calcium

Na2(SO4) - sodium

Naming Ionic Compounds

Step two – Name the second ion

Ex. CaCl2 –Calcium Chloride

Na2(SO4)-sodium sulfate

PROBLEM-Group B

Ex. Fe2O3 and FeO are different compounds

Fe3+ O2- = Fe2O3

Fe2+ O2- = FeO

Solution-Roman Numerals

Same naming scheme

Add a Roman Numeral to

identify the charge of the

metal.

Solution-Roman Numerals

Fe3+ O2- = Fe2O3

Fe2+ O2- = FeO

Fe2O3 = iron(III)Oxide

FeO = iron(II)Oxide

BONDING REVIEW-