The Name’s BOND…….

Chemical Bond

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 electrons

Gain 3 electrons

Gain 2 electrons

Cations/Anions

What kind of atoms LOSE electrons and become positive?

What kind of atoms GAIN electrons and become negative?

Diatomic Molecules

Always exist in a chemical bond with another atom, even if the atom is of the same element

H2 , N2 , O2 , F2 , Cl2 , Br2 , I2

Chemical Bond

Involves 2 atoms

Mutual, electrical attraction between nuclei and valence electrons of 2 atoms

Chemical bonds: an attempt to fill electron shells

1. Ionic bonds –

2. Covalent bonds –

3. Metallic bonds

IONIC BONDbond formed between

two ions by the transfer of electrons.

ELECTRON STEALING !

Ionic Bonds: One Big Greedy Thief Dog!

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+

Ionic Bonds

Between atoms of metals and nonmetals with very different electronegativity Huge difference in electronegativity Electronegativity value > 1.7

Bond formed by transfer of electrons

Produce charged ions

Form between elements located on opposite sides of the periodic table

Ionic Bonds (cont.)

Conductors

High melting point.

Water soluble

Crystallize (form crystals)

Examples; NaCl, CaCl2, K2O

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

COVALENT BONDbond formed by the sharing of electrons

Electron sharing!

Covalent Bond

Between nonmetallic elements of similar electronegativity. Small electronegativity difference <1.7

Formed by sharing electron pairs,

Formed between elements on the same side of the periodic table.

Covalent Bond (cont.)

Stable non-ionizing particles

Poor electrical conductors

Brittle, nonmetals, low melting point

Examples; O2, CO2, C2H6, H2O,

Partial Charges

Apply ONLY to COVALENT bonds

Results when there is unequal sharing between 2 atoms

Indicates electronegativity difference between bonded atoms

when electrons are shared equally, small electronegativity difference

NONPOLAR COVALENT BONDS

H2 or Cl2

when electrons are shared but shared

unequally

POLAR COVALENT BONDS

H2O

Polar Covalent Bonds--More

One atom “keeps” electrons closer to it

Electrons tend to reside around one atom more than the other atom

Electrons still remain distributed between the 2 atoms--unequal

Polar Covalent Bonds: Unevenly matched, but willing

to share.

Example: Cl2 , H2O

Multiple Covalent Bonds

Single 1 bond between 2 atoms 2 electrons shared Ex. H2

Double 2 bonds between 2 atoms 4 electrons shared Ex. O2

Multiple Covalent Bonds (cont.)

Triple 3 bonds between 2 atoms 6 electrons shared Ex. N2

Example: H2O, KI

Identify Bond type, Draw Lewis Structure

to show bonding

NaCl, CO

METALLIC BOND

bond found in metals; holds

metal atoms together

very strongly

Electrons

Localized: Electrons hang out in a local area Restricted to an atom/ion or shared between

atoms

Delocalized: Electrons not attached to a particular area Electrons are able to travel and move among

atoms

Metallic Bonds

Formed between atoms of metallic elements Between atoms on left side of periodic table Electronegativities are approximately equal

Electron cloud around atoms, delocalized electrons Valence electrons shared among multiple

atoms, “neighbors”

Electrons move through the whole metal, can jump between energy levels to create conduction bands.

Metallic Bonds (cont.)

Delocalized electrons result in good electrical and thermal conductors

3-D network of metal ions and electron sea

Examples; Na, Fe, Al, Au, Co

Metallic Bond, A Sea of Electrons

Metallic Bonds: Mellow dogs with plenty of bones to go

around.

Alloys

Metallic compounds with 2 different elements

Enhances metallic characteristics

Ex. Sterling silver (approx. 92-93%Ag, other metal—Cu) Brass (Cu and Zn) Stainless steel (contains chromium, prevents

corrosion, structural component)

What is the point of chemical bonding?

Physical/chemical properties vary based on Structure Bond type

Ionic Bonds High melting point High boiling point

Covalent Bonds Lower melting point Lower boiling point