Chapter 3

Chemical Bonds

Chemistry B11

1. Ionic bonds

2. Covalent bonds

3. Metallic bonds

4. Hydrogen bonds

5. Van der Waals forces

Chemical Bonds

1. Ionic bonds

2. Covalent bonds

Chemical Bonds

Review

Shell 1

Main-group elements

1A – 8A

Maximum 2 electrons in valence shell

Hydrogen and Helium

Other Shells Maximum 8 electrons in valence shell

Octet rule

Goal of atoms Filled valence shellNoble gases

(Stable)

Na+: 1s2 2s2 2p6

+ e-

Na: 1s2 2s2 2p6 3s1 Ne: 1s2 2s2 2p6

Ar: 1s2 2s2 2p6 3s2 3p6

Octet rule

Goal of atoms Filled valence shell

+ e-

Ar: 1s2 2s2 2p6 3s2 3p6

Noble gases (Stable)

Cl: 1s2 2s2 2p6 3s2 3p5 Cl-: 1s2 2s2 2p6 3s2 3p6

Na+: 1s2 2s2 2p6

+ e-

Na: 1s2 2s2 2p6 3s1 Ne: 1s2 2s2 2p6

Octet rule

Goal of atoms Filled valence shellNoble gases

(Stable)

Mg2+: 1s2 2s2 2p6

+ 2e-

Mg: 1s2 2s2 2p6 3s2 Ne: 1s2 2s2 2p6

Octet rule

Goal of atoms Filled valence shellNoble gases

(Stable)

Mg2+: 1s2 2s2 2p6

+ 2e-

Mg: 1s2 2s2 2p6 3s2 Ne: 1s2 2s2 2p6

+ 2e-

O: 1s2 2s2 2p4 O2-: 1s2 2s2 2p6 Ne: 1s2 2s2 2p6

Metals: lose 1, 2 or 3 e- Cation (Y+)

Nonmetals: gain 1, 2 or 3 e- Anion (X-)

Ions

Cation (Y+): Na+ Li+ Ca2+ Al3+

Anion (X-): Cl- F- O2-

Number of protons and neutrons in the nucleus remains unchanged.

Transition elements

1A 2A 3A 4A 5A 6A 7A 8A

Two problems of Octet rule

1. The octet rule cannot be used for transition and inner transition elements.

Fe2+ Fe3+ Cu1+ Cu2+

2. Ions of period 1 and 2 elements with charges greater than +2 are unstable.

C4+ C4- B3+C B

unstable unstable

Naming Monatomic Cations

International Union of Pure and Applied Chemistry (IUPAC) systematic names

Name of the metal + “ion”

H+ Hydrogen ionLi+ Lithium ion

Ca2+ Calcium ionAl3+ Aluminum ion

Cu1+ Copper(I) ionCu2+ Copper(II) ion

Fe2+ Iron(II) ionFe3+ Iron(III) ion

Hg+ Mercury(I) ionHg2+ Mercury(II) ion

Sn2+ Tin(II) ionSn4+ Tin(IV) ion

Naming Monatomic Cations

common name

Name of the metal +“-ous” smaller charge

“-ic” larger charge

Cu1+ Copper(I) ion Cuprous ionCu2+ Copper(II) ion Cupric ion

Fe2+ Iron(II) ion Ferrous ionFe3+ Iron(III) ion Ferric ion

Hg+ Mercury(I) ion Mercurous ionHg2+ Mercury(II) ion Mercuric ion

Sn2+ Tin(II) ion Stannous ionSn4+ Tin(IV) ion Stannic ion

Naming Monatomic Anions

Stem part of the name + “-ide”

Anion Stem name Anion name

F- fluor Fluoride ion

Cl- chlor Chloride ion

Br- brom Bromide ion

I- iod Iodide ion

O2- ox Oxide ion

S2- sulf Sulfide ion

P3- phosph Phosphide ion

N3- nitr Nitride ion

Naming Polyatomic Ions

Cation: NH4+ Ammonium

Anion:

OH- Hydroxide

NO2- Nitrite

NO3- Nitrate

SO32- Sulfite

SO42- Sulfate

HSO3- Hydrogen Sulfite

(bisulfite)

HSO4- Hydrogen sulfate

(bisulfate)

MnO4- Permanganate

CrO42- Chromate

Cr2O72- Dichromate

CO32- Carbonate

HCO3- Hydrogen Carbonate

(bicarbonate)

PO33- Phosphite

PO43- Phosphate

HPO42- Hydrogen phosphate

H2PO4- Dihydrogen phosphate

Ionic bonds

Metal-Nonmetal

Na: 1s2 2s2 2p6 3s1 Cl: 1s2 2s2 2p6 3s2 3p5

AnionCation

Na+: 1s2 2s2 2p6 Cl-: 1s2 2s2 2p6 3s2 3p6

Sodium (Na)

NaCl

Chlorine (Cl)

matter are neutral (uncharged):

total number of positive charges = total number of negative charges

Na+ Cl- NaCl

Ca2+ Cl- CaCl2

Al3+ S2- Al2S3

Ba2+ O2- Ba2O2 BaO

Molecule of NaCl Formula of NaCl

matter are neutral (uncharged):

total number of positive charges = total number of negative charges

Na+ NO3- NaNO3

Ca2+ CO32- Ca2(CO3)2 Ca(CO3)

Al3+ SO42- Al2(SO4)3

Mg2+ NO2- Mg(NO2)2

Naming Binary Ionic compounds

name of metal (cation) + name of anion

NaCl sodium chlorideCaO calcium oxide

Cu2O copper(I) oxide cuprous oxideCuO copper(II) oxide cupric oxide

Naming Polyatomic Ionic compounds

BaCO3 barium carbonate

Li2SO4 lithium sulfate Li2SO3 lithium sulfite

Covalent bonds

Nonmetal-NonmetalMetalloid-Nonmetal

Sharing ofvalence electrons

Lewis Dot Structure

H He Li CAl N Cl

H H Or H H

Or Cl H

Lewis Structure

HCl

Cl: 1s2 2s2 2p6 3s2 3p5

H: 1s1 He: 1s2

Ar: 1s2 2s2 2p6 3s2 3p6

HCl x

Shared pair of electrons(bonding pair of electrons)

Unshared pair of electrons(nonbonding pair of electrons) - (Lone pair)

Only valance electrons are involved in bonding (ionic and covalent bonds).

Electronegativity

A measure of an atom’s attraction for the electrons

Electronegativity Ionization energy

Covalent bonds

Nonpolar covalent bond: electrons are shared equally.

Polar covalent bond: electrons are shared unequally.

H Clδ+ δ-

Dipole

Electronegativity & bonds

Electronegativity Difference Between Bonded Atoms Type of Bond

Less than 0.5 Nonpolar Covalent

0.5 to 1.9 Polar Covalent

Greater than 1.9 Ionic

H H 2.1 – 2.1 = 0 Nonpolar covalent

N H 3.0 – 2.1 = 0.9 polar covalent

Na F 4.0 – 0.9 = 3.1 Ionic

Covalent compounds

H – C – H

–OCH2O H C H

OH – C – H

–O

H C H

O –

Correct

H C HH

HH – C – H

–H

–

H

CH4

H – N – H

–HNH3 H N H

H

H C C H

C – C

C2H4

H H

HH

H

H

H C C H

C = C

H H

HH

H

H

H C C H

H – C – C – H

C2H2H C C H

H – C C – H

Correct

Naming Binary Covalent compounds

Mono – Di – Tri – Tetra – Penta – Hexa – Hepta – Octa – Nona – Deca

1. Don’t use “mono” for the 1st element.

2. Drop the “a” when followed by a vowel.

NO2 nitrogen dioxide

N2O4 dinitrogen tetroxide

CCl4 carbon tetrachloride

S2O3 disulfur trioxide

prefix and full name of the first element in formula + prefix and the anion nameof the second element + “ide”

VSEPR Model

VSEPR: Valence-Shell Electron-Pair Repulsion method

Bond angle: angle between two atoms bonded to a central atom.

Each region of electron likes to be as far away as possible from the others.

Regions of electron density

Four regions of electron density around an atom:

Bond Angles in covalent molecules

Linear molecules

Trigonal planarmolecules

Tetrahedral molecules

2 regions

3 regions

4 regions

Unshared electron paires

H2OCH4 NH3

Polarity

1. Molecule has polar bonds.2. Its centers of δ+ and δ- lie at different places (sides).

O = C = O

δ- δ+ δ-

nonpolar molecule

H – C – H–H

–

H

δ+

δ+

δ+

δ+

δ-

C

=O

H Hδ+

δ-

polar molecule

N

HH H

δ-

δ+