MakingMakingBonding Bonding ModelsModels

Today We Will…Today We Will…

Describe the two main ways Describe the two main ways elements bondelements bond

Construct Lewis Dot DiagramsConstruct Lewis Dot DiagramsIdentify characteristics of Identify characteristics of

Ionic and CompoundsIonic and CompoundsDefine cation and anionDefine cation and anion

BondingBonding BondingBonding is the sharing or transferring is the sharing or transferring

of electrons between elements in of electrons between elements in order to combine to form molecules or order to combine to form molecules or compounds.compounds.

Types of BondsTypes of BondsMetal + Nonmetal = Metal + Nonmetal = Ionic Ionic

(transfer)(transfer)

Nonmetal + Nonmetal = Nonmetal + Nonmetal = CovalentCovalent (share)(share)

Metal + Metal = Metal + Metal = MetallicMetallic (sea (sea of electrons)of electrons)

Bonding possibilitiesBonding possibilities(1) They can try to (1) They can try to gaingain electrons to electrons to

fill up their last shell. fill up their last shell. (IONIC)(IONIC)OROR

(2) They (2) They givegive up electrons and have up electrons and have a filled lower shell. a filled lower shell. (IONIC)(IONIC)

OROR(3) They (3) They shareshare a few electrons and a few electrons and

have a filled shell. have a filled shell. (COVALENT)(COVALENT)

Lewis Dot DiagramsLewis Dot Diagrams Discovered by LewisDiscovered by Lewis It is a diagram for each element that It is a diagram for each element that

depicts that element’s valence electronsdepicts that element’s valence electrons Valence Electrons: electrons on the outer Valence Electrons: electrons on the outer

shell of an element.shell of an element. This will helpThis will help

us tell howus tell how

elements will elements will

bond!!!bond!!!

Learning Check Learning Check

A. X would be the electron dot formula forA. X would be the electron dot formula for

1) Na1) Na 2) K2) K 3) 3) AlAl

B. B. X X would be the electron dot formula would be the electron dot formula

1) B1) B 2) N2) N 3) P 3) P

How do we know the valence electrons of an How do we know the valence electrons of an

element?element? GROUPS!!GROUPS!! Label the valence electrons according to their Label the valence electrons according to their

groups.groups.

Ionic BondIonic BondDefinition:-bond formed between two Definition:-bond formed between two

ions by the ions by the transferringtransferring of of electronselectrons

Ionic bonds only form between a Ionic bonds only form between a metal and a nonmetal with different metal and a nonmetal with different electronegativities. electronegativities.

Electronegativity- tendency of an Electronegativity- tendency of an atom to attract electronsatom to attract electrons

The more electrons the atom has the The more electrons the atom has the more elctronegative it is. more elctronegative it is.

Which has the highest Which has the highest electronegativityelectronegativity

Ionic Bonds form IonsIonic Bonds form Ions

• Metals become Metals become cations (+ cations (+ charged)charged)

• Nonmetals become Nonmetals become anions (-anions (-charged)charged)

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

Helium, neon and argon are atoms which do not react with other atoms.

Each of these gases has a full outer electron shell (orbit).

2p2n 10p10n 18p22n

He 42

2010Ne

Ar 1840

2,82,8,8

Na

e.c. 2,8,1

(Na +)

Ion

Atom

e.c. (2,8)+The Sodium loses 1 electron to leave a complete outer shell.

It is now a Sodium ion with a charge of 1 +

The Sodium atom has 1 Electron in it’s outer shell.

+

All Things Science - Ionic and covalent bonding animation.mht

Chemical Bonds.mht

Cl

e.c. 2,8,7

(Cl - )

Ion

Atom

e.c. (2,8,8)-The Chlorine gains 1 electron to gain a complete outer shell.

It is now a Chlorine ion with a charge of 1 -

The Chlorine atom has 7 electrons in it’s outer shell.

-

Oxidation NumbersOxidation Numbers The plus or minus indicates if electrons were lost The plus or minus indicates if electrons were lost

or gained. or gained. The number indicates how many electrons. The number indicates how many electrons.

Ionic BondIonic Bond

1.1. Write the symbol for each Write the symbol for each elementelement

2.2. Draw the Electron Dot DiagramDraw the Electron Dot Diagram

3.3. Draw an arrow to show the Draw an arrow to show the transfer of electronstransfer of electrons

4.4. Make sure the sum of the ions Make sure the sum of the ions equals zeroequals zero

Ionic BondIonic Bond

1.1. Write the symbol for each Write the symbol for each elementelement

2.2. Draw the Electron Dot DiagramDraw the Electron Dot Diagram

3.3. Draw an arrow to show the Draw an arrow to show the transfer of electronstransfer of electrons

4.4. Make sure the sum of the ions Make sure the sum of the ions equals zeroequals zero

Ionic BondIonic Bond

Magnesium (Mg) + Fluorine (F)Magnesium (Mg) + Fluorine (F)

Don’t forget to show the oxidation Don’t forget to show the oxidation number and the chemical formula.number and the chemical formula.

Ionic Compounds

• Held together by strong electrostatic forces

• High melting points and boiling points

• When melted or dissolved ionic compounds conduct electricity

Covalent BondingCovalent Bonding

Today We Will Today We Will

Describe and draw covalent bonding Describe and draw covalent bonding Identify characteristics of covalent Identify characteristics of covalent

compoundscompounds Define diatomic atomDefine diatomic atom

Lets Review Lets Review

How many valence electrons makes an How many valence electrons makes an atom stable? What is this called? atom stable? What is this called?

Draw the Lewis Dot Diagram for SulfurDraw the Lewis Dot Diagram for Sulfur An ionic bond is between a _______ and a An ionic bond is between a _______ and a

______. ______. An ionic bond forms when electrons are An ionic bond forms when electrons are

_______ or _______. _______ or _______.

Covalent BondCovalent Bond

Atoms still want to achieve Atoms still want to achieve a noble gas configuration. a noble gas configuration.

Bond formed by sharing Bond formed by sharing electronselectrons

Occurs between non metalsOccurs between non metals Results in the formation of Results in the formation of

a moleculea molecule

Covalent BondCovalent Bond

1.1. Write the symbol for each elementWrite the symbol for each element

2.2. Draw the Electron Dot DiagramDraw the Electron Dot Diagram

3.3. Rearrange the electrons to pair up Rearrange the electrons to pair up with electrons from each atomwith electrons from each atom

4.4. Draw circles to show sharing of Draw circles to show sharing of electronselectrons

5.5. Draw the bond structure for each Draw the bond structure for each pair of electrons shared.pair of electrons shared.

Covalent BondCovalent Bond

Hydrogen (H) + Hydrogen (H) Hydrogen (H) + Hydrogen (H)

H° °H

Each hydrogen atom wants to gain one electron to achieve an octet

The octet is achieved by each atom sharing the electrons in the middle.

Covalent BondCovalent Bond

Hydrogen (H) + Hydrogen (H) Hydrogen (H) + Hydrogen (H)

H° °H

The pair shared in the middle is called a bonding pair. Since there is only one bonding pair we call this a single bond.

Covalent BondCovalent Bond

Hydrogen (H) + Hydrogen (H) Hydrogen (H) + Hydrogen (H)

H H

Single bonds are represented with a dash.

Oxygen atoms are highly electronegative.

So both atoms want to gain two electrons.

OO

OOBoth electron pairs are shared.

6 valence electronsplus 2 shared electrons

= full octet

OO

two bonding pairs,

OOmaking a double bond

Diatomic AtomsDiatomic Atoms

Elements that are naturally in molecules Elements that are naturally in molecules with 2 atoms eachwith 2 atoms each

H O N Cl Br I FH O N Cl Br I F

Covalent CompoundsCovalent Compounds

Forces between molecules are weak. Forces between molecules are weak. Usually gas or liquidsUsually gas or liquids Low melting point and boiling pointLow melting point and boiling point No overall electrical chargeNo overall electrical charge

Classwork/HomeworkClasswork/Homework

1.1.HH22S S

2.2.FF22

3.3.HF HF

4.4.HH22O O

5.5.AlFAlF33

6.6.MgO MgO

1.1. NHNH33

2.2. PBrPBr33

3.3. CClCCl44

4.4. CSCS2 2

5.5. COCO22

6.6. KK22S S

7.7. CHCH44