LewisLewis DotDot

StructuresStructures

IonicIonic & Metallic Bonding& Metallic Bonding

And…And…

Chemistry Joke

Q: What is Mickey Mouse’s favorite element?

A: Plutonium!!!!

Valence ElectronsValence ElectronsElectrons in the outer energy level.Electrons in the outer energy level.Determine chemical and physical Determine chemical and physical

properties of an elementproperties of an elementThe group number of the representative The group number of the representative

elements is the elements is the samesame as the number of as the number of valence electrons.valence electrons.

All of the elements within a given group All of the elements within a given group will have the same number of valence will have the same number of valence electrons.electrons.

For example:For example: Be is in Group 2A.Be is in Group 2A.There are 2 electrons in the There are 2 electrons in the

outermost energy level. outermost energy level. Be has an eBe has an e configuration of 1s² 2s² configuration of 1s² 2s²How many valence electrons will F How many valence electrons will F

have?have?

ValenceValence ElectronsElectrons

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Lewis Dot Diagrams and the Octet Rule

•Noble gases have a FULL valence shell of 8 electrons (ns2np6).

•(Helium has a full valence shell with only 2 valence electrons.)

•Through bonding, other atoms “seek” a full shell of eight electrons.

•This is called the OCTET RULE.•Noble gases are unreactive (inert) because they already have a full shell!

Valence ElectronsValence Electrons

Lewis Dot Diagrams and the Octet Rule

•A visual representation of where the bonding electrons are in an atom

•The VALENCE electrons are shown as dots around the symbol for the element.

•This is called an electron dot diagram or a Lewis dot structure.

Electron Dot DiagramsElectron Dot Diagrams

HOW TO MAKE A DOT DIAGRAMHOW TO MAKE A DOT DIAGRAM Write the symbol for the element. Write the symbol for the element. Decide how many valence electrons the Decide how many valence electrons the

element has.element has. Using dots, place one dot per electron on Using dots, place one dot per electron on

each side of an imaginary box around the each side of an imaginary box around the symbol.symbol.

You must place one dot on each side of the You must place one dot on each side of the box before doubling up.box before doubling up. Otherwise, the order doesn’t matter.Otherwise, the order doesn’t matter.

N

5

N

ElectronElectron DotDot DiagramsDiagrams

Lithium has only 1 valence electron, so we Lithium has only 1 valence electron, so we only place one dot on our diagram. only place one dot on our diagram.

LithiumLithium

LiLi

1 valence electron!1 valence electron!

ElectronElectron DotDot DiagramsDiagrams

Beryllium has 2 valence electrons, so we Beryllium has 2 valence electrons, so we place two dots on our diagram. place two dots on our diagram.

BerylliumBeryllium

BeBe

BeBe

IonicIonic BondingBonding An atom is always trying to get a full outer An atom is always trying to get a full outer

energy level of eight electrons—Octet Rule.energy level of eight electrons—Octet Rule.

Atoms can gain, lose, or share valence (outer) Atoms can gain, lose, or share valence (outer) electrons to complete their outer shell.electrons to complete their outer shell.

When atoms get their full shells by completely When atoms get their full shells by completely giving or taking electrons from other atoms, an giving or taking electrons from other atoms, an Ionic Bond Ionic Bond is formedis formed..

IonicIonic BondingBonding Involves Involves

A metal and a nonmetalA metal and a nonmetal• A positively charged ion ( A positively charged ion ( the metalthe metal) ) • A negatively charged ion (A negatively charged ion (the nonmetalthe nonmetal))

An electrostatic attraction happens!An electrostatic attraction happens!• (One atom loses an electron, the other (One atom loses an electron, the other

gains it. They become oppositely charged gains it. They become oppositely charged ““bondbond”” together!) together!)

IonicIonic BondingBonding Are these pairs likely to form ionic Are these pairs likely to form ionic

compounds?compounds? Cl, BrCl, Br

K, He K, He

Na, ClNa, Cl

No—Both nonmetals that form negative ions.

No—Helium is a noble gas that doesn’t bond with anything.

Yes—Sodium is a metal that forms a positive ion, and chlorine is a nonmetal that forms a negative ion.

IonicIonic BondingBonding

Na Cl+ -

Two ions now Two ions now stuck together!stuck together!

NaCl

Let’sLet’s Look at This Reaction:Look at This Reaction: http://www.visionlearning.com/library/http://www.visionlearning.com/library/

module_viewer.php?mid=55module_viewer.php?mid=55

http://www.youtube.com/watch?v=Mx5JJWI2aaw

4 Properties4 Properties ofof IonicIonic CompoundsCompounds1.1. At room temp. most ionic compounds are a At room temp. most ionic compounds are a

crystalline solidcrystalline solid2.2. Ionic compounds are Ionic compounds are brittlebrittle and shatter if hit and shatter if hit

Ions of like charge are forced near each Ions of like charge are forced near each other.other.

3.3. Because of the strong electrostatic attractions, Because of the strong electrostatic attractions, crystalline solids are crystalline solids are very stablevery stable and have high and have high melting points!melting points!

4.4. When melted or dissolved, ionic compounds When melted or dissolved, ionic compounds can can conduct electricityconduct electricity!!

All of the charged All of the charged particles (ions) particles (ions) enable a flow of enable a flow of current.current.

SaltSalt waterwater

SugarSugar waterwater

Metallic BondingMetallic Bonding

The mobile valence electrons make them The mobile valence electrons make them good good conductors conductors of heat and electricity!of heat and electricity!

Metals are made of closely packed cations with Metals are made of closely packed cations with mobile “de-localized” valence electrons.mobile “de-localized” valence electrons.

The attraction of The attraction of the free-floating the free-floating valence electrons valence electrons for the positively for the positively charged metal charged metal ions forms the ions forms the metallic bond.metallic bond.

MalleableMalleable – able to be – able to be pounded into sheets. pounded into sheets. Metals do not shatter as Metals do not shatter as

mobile electrons keep mobile electrons keep the positive metal ions the positive metal ions from getting too close to from getting too close to each other.each other.

DuctileDuctile – able to be – able to be drawn into wiresdrawn into wires

Chemistry Joke

Q: What does T. A. B. L. E. stand for?

A: The Periodic Table!