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 18

H 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 crystalline 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 ions are free to move).

• Are more soluble in water than other solvents

Properties of ionic compounds

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Ex.

• Write

a)Lewis (electron-dot) formula

b)Chemical formula

of the compound formed b/ Mg and O.

Ex.

• Write

a)Lewis (electron-dot) formula

b)Chemical formula

of the compound formed b/ Al and S.

NAMING IONIC COMPUNDS (P.100)

• Name of the metal+ ionic name of the nonmetal

Name of the metal+ name of the polyatomic ion

NAMING IONIC COMPUNDS

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

Name of the metal (oxidation state of the metal in Roman numeral) + name of the polyatomic ion

Compounds Made with Variable Charged Metals

NAMING IONIC COMPOUNDS

• NaBr

• FeCl2

• Mg3N2

• Al4C3

• CuO

• LiH

• K3P

• PbO2

• CuS

NAMING IONIC COMPOUNDS

• BaCO3

• Zn(NO3)2

• Rb3PO4

• 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 sharing of electrons in HF is unequal: the fluorine atom attracts electron density away from the hydrogen (the bond is thus a polar covalent bond)

• The H-F bond can thus be represented as:

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Electronegativity and bond polarity

The ‘ δ+' and ' δ -' symbols indicate partial positive and negative charges.The arrow indicates the "pull" of electrons off the hydrogen and towards the more electronegative atom

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

HCl:

Atoms that are out of duet and octet rules:

Be,B

Naming covalent compounds

• (prefix to indicate the number of 1st nonmetal+name of 1st nonmetal) + (prefix to indicate the number of 2nd nonmetal+ ionic name of second nonmetal)

Naming covalent compounds

• For you own information, here is some other generally useful information:

• Roman Numerals

• I = 1; II = 2; III = 3; IV = 4; V = 5; VI = 6; VII = 7.

• Prefixes:

• mono = 1; di = 2; tri = 3; tetra = 4; penta = 5; hexa = 6; hepta = 7; octa = 8.

Naming covalent compounds

• N2O3

• N2 O5

• Cl3F

• Cl2O7

• Cl2O

• PCl3

• SF4

• P2S3

Naming compounds including polyatomic ions only

• Name of 1st polyatomic ion + Name of 2nd polyatomic ion

Naming covalent compounds

• (NH4)3PO4

• (NH4)2SO4

• (NH4)2S

• NH4Cl

• (NH4)2CO3

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…)

Bond Bond formationformation

Bond Bond formationformation

ClH H Cl••

••

••

••

••

••

+

Notice 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::

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

•

••

•

••

H ClLone pair electrons

Bonding electrons

LEWIS LEWIS formformula!!!ula!!!

HCl

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

All diatomic molecules have a linear geometry…

VSEPR

1)Linear geometry

Number of lone pair electrons around the

central atom: 0 

Example:CO2

HCN 

3) Tetrahedral Geometry:

Number of lone pair electrons

around the central atom: 0

  Example:

CH4

CCl4

 

4) Trigonal pyramid geometry:

Number of lone pair electrons

around the central atom : 1

  Example;

NH3

NF3

 

5)Bent/ V-shape/Angular geometry:

Number of lone pair electrons

around the central atom : : 2

  Example;

H2O

ClO2

OF2