Chemical Bond

• The interaction b/ atoms/ions that results in a decrease in potential energy of the system which hence becomes stable.

Electron -dot(Lewis) symbols

Valence electrons are shown as dots around the symbols of the atoms.

1 2 13 14 15 16 17 18H He:

Li Be B C N O : F :Ne :

Na Mg Al Si P S :Cl :Ar :

Types of bonds

• Ionic• Covalent• Metallic

IONIC BONDThe Electrostatic

attraction forces happen b/ metal and nonmetal

ions as a results of exchanging electrons.

Ionic Bonds: One Big Greedy Thief Dog!

-have crystalline structure formed of repeating units).

-ions stay together as a result of attraction b/ oppositely charged ions.

-The 3D structure of the crytalline is named as :lattice.”

Properties of ionic compounds

• Hard, brittle.• Relatively high melting and boiling points• Do not conduct the electricity when solid

but do when molten or in aqueous solution (since the electrons are free to move).

• Are more soluble in water than other solvents

Properties of ionic compounds

Ex.

• Write a)Lewis (electron-dot) formula b)Chemical formulaof the compound formed b/ Mg and O.

Ex.

• Write a)Lewis (electron-dot) formula b)Chemical formulaof the compound formed b/ Al and S.

NAMING IONIC COMPUNDS (P.100)

• Name of the metal+ ionic name of the nonmetal

Compounds Made with Variable Charged Metals

Name of the metal (oxidation state of the metal in Roman numeral) + ionic name of the nonmetal

NAMING IONIC COMPOUNDS• NaBr• FeCl2

• Mg3N2

• Al4C3

• CuO• LiH• K3P• PbO2

• CuS

NAMING IONIC COMPOUNDS• BaCO3

• Zn(NO3)2

• Rb3(PO4)• Fe(OH)3

• AgHCO3 CoI2

• CaSO4 NiCr2O7

• CuOH CrCrO4

• MnO2 KMnO4

• K2C2O4 Sr(ClO4)2

COVALENT BOND:Happens b/ nonmetal atoms as a result of sharing electrons.

• Many interactions are present:– The attraction

forces b/ the electrons and nucleus

– Repulsion forces b/ the electrons

– Repulsion forces b/ the nuclei

The shared electrons are attracted w/ an equal power

by both atoms in the bonding.

NONPOLAR COVALENT BOND:

H2 , Cl2,Br2,Cl2,O2,N2

Oxygen AtomOxygen Atom Oxygen AtomOxygen Atom

Oxygen Molecule (O2)

H2,Cl2:

The shared electrons are NOT attracted w/ an equal power by

the atoms in the bonding.

POLAR COVALENT BOND:

H2O,HF, HCl,NH3,CH4

The bond gets polar as the difference in the electronegativities of the atoms bonded increases.

HCl:

Bond length Bond energy

CCC

C

CC

154 pm134 pm120 pm 835 kJ/mol

602 kJ/mol346 kJ/mol

Bond length:The average distance b/ the nuclei of the atoms when the attraction and repulsion forces b/ the atoms are balanced.

Bond length: C-C > C=C > C≡CBond energy: C-C < C=C < C≡C

Dublet(duet) Rule: Completion of valence electron number to 2 when atoms make bonds in order to reach the stability of He (H,Li).

Octet Rule: Completion ve number to 8 when the atoms make a bond in order to reach the stability of Noble gases. (O,N,F,C,Cl,Br,I,P,S…)

Atoms that are out of duet and octet rules:

Be,B

Multiple bondsMultiple bonds::

Multiple bondsMultiple bonds::

Sigma and Pi bonds

• Sigma bonds happen as a results of tip-to-tip overlap of the orbitals of the atoms.

• Pi bonds happen as a result of side-to-side overlap of the orbitals of the atoms.

2 atoms- Can only make 1 sigma bond.- Can make more than 1 pi bond.Pi bonds are weaker than sigma bonds!!!

Sigma and Pi bonds

Bond Bond formationformationA covalent bond is formed as a result of overlap A covalent bond is formed as a result of overlap

of atomic orbitals.of atomic orbitals.

ClH H Cl••

••

••

••••

••+

H (1s) and Cl (2p) overlapNotice that each atom has one Notice that each atom has one

unpaired electronunpaired electron!!!!!!!!!!

Cov. Bond and lone (non-Cov. Bond and lone (non-bonding) electronsbonding) electrons::

•••

•••

H ClLone pair electronsBonding electrons

LEWIS LEWIS formformula!!!ula!!!

HCl

WARNING!!!!!!!!!!!!

All diatomic molecules have a linear geometry…

VSEPR TheoryVSEPR TheoryValenceShellElectronPair Repulsion

N

H

HH

- Polar moleküller dipole moment değerine sahiptirler.(vektörel büyüklük)

- Eğer bu dipoller eşit büyüklükte iseler ve toplamları sıfır ediyorsa, molekül apolar bir moleküldür.

H F H F

Molekül polarlığı = bağ polarlığı

CO2 - Nonpolar H2O - Polar

1)Doğrusal GeometriSigma bağ

sayısı:2

merkez atom etrafında yalnız elektron çifti: 0

  Örnek:BeH2

CO2

HCN 

2) Düzlem üçgen Geometri

Sigma bağ sayısı:3

merkez atom etrafında yalnız elektron çifti: 0

  Örnek;

BF3

CO32-

COCl2

 

3)Düzgün dörtyüzlü Geometri:Sigma bağ

sayısı:4

merkez atom etrafında yalnız elektron çifti: 0

  Örnek;

CH4

CCl4

SO42-

 

4) Üçgen piramit Geometri:Sigma bağ

sayısı:3

merkez atom etrafında yalnız elektron çifti: 1

  Örnek;

NH3

NF3

PCl3

 

5)Kırık doğru/açısal Geometri:Sigma bağ

sayısı:2

merkez atom etrafında yalnız elektron çifti: 2

  Örnek;

H2OClO2

OF2

 

2.PERİYOT ELEMENTLERİNİN BAĞ OLUŞUMLARI:

4Be:

sp2 Hibritleşmesi

4 atomic orbitals{2s + 2px + 2pz }, 2py

yield 3 sp2 hybrid orbitals+ 1 py

sp2 HAO directed to the corners of a triangle (trigonal

planar)

s p psp2

+

+

+

5B:

120o

s + 2 p

=

3 sp2 orbitalleri

sp2 Hibritleşmesi

5B:

sp3 Hybridization of Atomic Orbitals

+

+ +

4 atomic orbitals2s + 2px + 2py + 2pz

yield4 hybrid atomic orbitals

4 sp3 orbitals

Four SP3 HAOs directed to the corners of a tetrahedron

s p 4 sp3

109.5o

6C:

electron shellsa) Atomic number = number of Electrons

b) Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.

c) Electron shells determine how an atom behaves when it encounters other atoms

Electrons are placed in shells according to rules:

1) The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons.

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons

C would like to N would like toO would like to

Gain 4 electronsGain 3 electronsGain 2 electrons

Why are electrons important?

1) Elements have different electron configurations different electron configurations mean

different levels of bonding

Chemical bonds: an attempt to fill electron shells

1. Ionic bonds – 2. Covalent bonds –3. Metallic bonds

Learning Check A. X would be the electron dot formula for

1) Na 2) K 3) Al

B. X would be the electron dot formula

1) B 2) N 3) P

Formation of Ions from Metals

Ionic compounds result when metals react with nonmetals

Metals lose electrons to match the number of valence electrons of their nearest noble gas

Positive ions form when the number of electrons are less than the number of protons

Group 1 metals ion 1+

Group 2 metals ion 2+

• Group 13 metals ion 3+

Formation of Sodium Ion

Sodium atom Sodium ion

Na – e Na +

2-8-1 2-8 ( = Ne)

11 p+ 11 p+

11 e- 10 e-

0 1+

Formation of Magnesium Ion

Magnesium atom Magnesium ion

Mg – 2e Mg2+

2-8-2 2-8 (=Ne)

12 p+ 12 p+

12 e- 10 e-

0 2+

Some Typical Ions with Positive Charges (Cations)

Group 1 Group 2 Group 13

H+ Mg2+ Al3+

Li+ Ca2+

Na+ Sr2+

K+ Ba2+

Learning Check

A. Number of valence electrons in aluminum1) 1 e- 2) 2 e- 3) 3 e-

B. Change in electrons for octet1) lose 3e- 2) gain 3 e- 3) gain 5 e-

C. Ionic charge of aluminum 1) 3- 2) 5- 3) 3+

Solution

A. Number of valence electrons in aluminum3) 3 e-

B. Change in electrons for octet1) lose 3e-

C. Ionic charge of aluminum 3) 3+

Learning Check

Give the ionic charge for each of the following:A. 12 p+ and 10 e-

1) 0 2) 2+ 3) 2-

B. 50p+ and 46 e-1) 2+ 2) 4+ 3) 4-

C. 15 p+ and 18e-2) 3+ 2) 3- 3) 5-

Ions from Nonmetal Ions

In ionic compounds, nonmetals in 15, 16, and 17

gain electrons from metals

Nonmetal add electrons to achieve the octet

arrangement

Nonmetal ionic charge:

3-, 2-, or 1-

Fluoride Ion

unpaired electron octet 1 -

: F + e : F :

2-7 2-8 (= Ne)

9 p+ 9 p+

9 e- 10 e- 0 1 -

ionic charge

Ionic Bond

• Between atoms of metals and nonmetals with very different electronegativity

• Bond formed by transfer of electrons• Produce charged ions all states. Conductors

and have high melting point.• Examples; NaCl, CaCl2, K2O

Covalent Bond

• Between nonmetallic elements of similar electronegativity.

• Formed by sharing electron pairs• Stable non-ionizing particles, they are not

conductors at any state• Examples; O2, CO2, C2H6, H2O, SiC

Bonds in all the polyatomic ions

and diatomics are all covalent bonds

- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

METALLIC BONDbond found in

metals; holds metal atoms together very strongly

Metallic Bond

• Formed between atoms of metallic elements• Electron cloud around atoms • Good conductors at all states, lustrous, very

high melting points• Examples; Na, Fe, Al, Au, Co

Metallic Bonds: Mellow dogs with plenty of bones to go around.

Ionic Bond, A Sea of Electrons

Metals Form Alloys

Metals do not combine with metals. They form Alloys which is a solution of a metal in a metal.Examples are steel, brass, bronze and pewter.

Formula Weights

• Formula weight is the sum of the atomic masses.

• Example- CO2

• Mass, C + O + O 12.011 + 15.994 + 15.99443.999

Practice• Compute the mass of the following compounds

round to nearest tenth & state type of bond:• NaCl; • 23 + 35 = 58; Ionic Bond• C2H6; • 24 + 6 = 30; Covalent Bond• Na(CO3)2; • 23 + 2(12 + 3x16) = 123; Ionic & Covalent