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Chemical Bonding

The keys to chemistry!

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Bonding3 types:

1.Ionic bondinge.g. Table Salt (NaCl)

2. Covalent bonding e.g. Water (H2O)

3. Metallic bonding e.g. Iron

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Chapter 15 Looks at:

Ionic bonding:Valence electrons are transferred between atoms

Metallic bonding:Valence electrons are mobile within the metal

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Valence ElectronsCan be determine from the electron configuration.

Na 2-8-1 1 valence e-

S 2-8-6 6 valence e-

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Lewis Dot Symbols(shows number of valence e-)

F

Na N

S

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Lewis Dot SymbolsYou Try It !!!

Write the dot structures for:

Al Ca

C Ne

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Def: Ionic Bond:The “electrostatic” attraction

between a cation (+) and an

anion (-).

NaCl

Cation+1 charge

Anion-1 charge

(charges not written)

+ -+ -

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Ionic Compounds: Review“Formula Unit”: the lowest ratio

of atoms in an ionic compound.

Formula unitis NaCl

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Ionic Formulas•Calcium bromide

Ca2+ Br-

CaBr2 (balance charge)

•Copper(I) sulfate

Cu+ SO42-

Cu2SO4

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Ionic Compounds: Try It

calcium nitrate

ammonium bromide

magnesium phosphate

calcium chromate

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The Octet Rule

When forming compounds, many atoms attain the electron configuration of a noble gas (8 valence electrons).

Ne (exception is He with 2 valence electrons)

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CationsMetals tend to lose valenceelectrons to achieve an octet.

Na[Ne]

Na+ + 1e-

Ca Ca2+ + 2e-

[Ar]

13Atomic War!!

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Cations

Cu+1

[Ar]3d10

-1e-Cu

[Ar]3d104s1

Transition metals are more complicated.

“pseudo noble gas” e- configuration

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AnionsMany nonmetals gain electrons to achieve an octet.

F F -+ e-

[Ne]

O O 2-+ 2e-

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Cations & Anions

Try It !!!

Write the dot structure for:

nitrogen atom nitride ion

chlorine atom chloride ion

magnesium atom magnesium ion

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Ionic Compounds

Li F+ Li+ F -

[He] [Ne]

When Li and F react, an e- is lost by Li and gained by F.

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Ionic Compounds: AlBr3Recall for ionic compounds, total charge must be zero.

Br

Al Br

Br

Al 3 Br+3 -

[Ne] [Kr]

Dot formula for a compound

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Ionic Compounds

Write dot structures for reactions of these atoms:

Cs + F

K + O (total number of dots

stays the same)

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Properties of Ionic Compounds

•solid at room temperature•high MP•conduct electrical current when

molten or in water (DEMO) “electrolyte”

(Strong electrostatic forces hold ions in place.)

Electrical Conductivity

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NaCl(s) Na+(aq) + Cl-(aq)H2O

mobile ions

Conduct electricity: • charged particle• free to move

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The Metallic Bond

What gives metals their special properties?

What holds metal atoms together?

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The Metallic BondRegularly spaced cations in a “sea” of valence electrons

++ + +

+ ++

+ + +++ +

e-e-

e-

e- e-

e-

e-

e-e-

e-e-

e-

e-

e-

e-

e-

e-Na+

valence e-

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Def: Metallic Bond:Attraction between fixedmetal cations and mobilevalence electrons.

•electrically conductive•heat conductive•malleable•ductile

explains

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Metals

High density because of “close-packed” cubic or hexagonal crystal structures.

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Alloy a solid solution of

two or more metals.

Sterling silver: 93%Ag, 7%Cu

Stainless steel: 81%Fe, 18%Cr, .4%C, 1%Ni

What is: bronze ?14 carat gold ?

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Don’t move or I’ll fill you full of 98% Pb, 1.0% Sb & 0.75 %Ag

What’s the name of that

alloy?

Chemists in the Wild West

A bullet !

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Warm-up

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Write the formula for tin(II) phosphate.

Write the e- dot symbol for:Al, S, Ag, I

Define “ionic bond”.

Warm-up

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What is the “octet rule?”Write the e- dot symbol for:

•barium•iodine•barium iodide