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REVIEW. We can tell how many electrons and atom will gain or lose by looking at its valence. Metals like to lose electrons. (Cations) Ex. Na + Nonmetals like to gain electrons. (Anions) Ex: O 2- All elements try to have a full valence of 8 electrons(OCTET RULE). REVIEW.

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Review
REVIEW

  • We can tell how many electrons and atom will gain or lose by looking at its valence.

  • Metals like to lose electrons. (Cations)

    • Ex. Na +

  • Nonmetals like to gain electrons. (Anions)

    • Ex: O 2-

  • All elements try to have a full valence of 8 electrons(OCTET RULE).


Review1
REVIEW

  • Cation- is a positively charged ion.

  • How do cations form?

    • When atoms LOSE electrons they become positive.

  • Anion- is a negatively charged ion.

  • How do anions form?

    • When atoms GAIN electrons they become negative.


Chemical bonding notes

Na

Cl

Chemical Bonding Notes

A chemical bond is the force of attraction that holds two atoms together.

Attractive Force



Why do elements form chemical bonds

Why do elements form chemical bonds?http://www.wisc-online.com/objects/ViewObject.aspx?ID=GCH2204

Atoms form chemical bonds in order to fill their outermost energy level with electrons.

A full valence shell causes an atom to be more stable.

A full valence shell consists of 8 valence electrons.


Ionic bonding

Ionic Bondinghttp://www.wisc-online.com/objects/ViewObject.aspx?ID=GCH2204

Ionic bonds: Metal atoms transfer electrons to nonmetal atoms. Producing oppositely charged ions (cation & anion) which attract each other.

Na + Cl Na+Cl-



How to write a formula
How to write a formula. form an octet.

  • Write cation first, followed by anion

  • Example:

    Anion : P3-

    Cation : Al3+

Formula : AlP


How to write a formula1
How to write a formula. form an octet.

Compound must be neutral, so all charges must cancel


Write an ionic formula for Na form an octet.+ bonding with F−

Balance the charges.

Na+ F−

(1+) + (1-) = 0

1 Na+ and 1 F− = NaF


Write an ionic formula for form an octet.

Mg2+ bonding with Cl−

Balance the charges.

Mg2+ Cl−

Cl−

(2+) + 2(1-) = 0

1 Mg2+ and 2 Cl− = Mg Cl2


Write an ionic formula for K form an octet.+ bonding with S2−

Balance the charges.

K+ S2−

K+

2(1+) + (2-) = 0

2 K+ and 1 S2− = K2S


Write the formula for
Write the formula for… form an octet.

an ionic compound composed of:

Al3+ and S2-

Al2S3


Write an ionic formula for Fe form an octet.3+ bonding with OH−

Balance the charges.

Fe3+ OH−

OH−

OH−

(3+) + 3(1-) = 0

1 Fe3+ and 3 OH− = Fe(OH)3


Let s play the ionic bonding dating game
Let form an octet.’s play the Ionic Bonding Dating Game!


Example aluminum chloride

Step 4: form an octet.AlCl

3

Example: Aluminum Chloride

Criss-Cross Rule

Aluminum Chloride

Step 1:

write out name with space

Al Cl

3+

1-

Step 2:

write symbols & charge of elements

Al Cl

Step 3:

1

3

criss-cross charges as subsrcipts

combine as formula unit

(“1” is never shown)


Example aluminum oxide
Example: Aluminum Oxide form an octet.

Criss-Cross Rule

Step 1: Aluminum Oxide

Step 2: Al3+ O2-

Step 3: Al O

2

3

Step 4: Al2O3


Example magnesium oxide
Example: Magnesium Oxide form an octet.

Criss-Cross Rule

Step 1: Magnesium Oxide

Step 2: Mg2+ O2-

Step 3: Mg O

2

2

Step 4: Mg2O2

Step 5: MgO


Criss cross rule
Criss-Cross Rule form an octet.

criss-cross rule:

charge on cation / anion

“becomes” subscript of anion / cation

** Warning: Reduce to lowest terms.

In3+ and Br1–

Al3+ and O2–

Ba2+ and S2–

In1 Br3

Al2 O3

Ba2 S2

Al2O3

BaS

InBr3

aluminum oxide

barium sulfide

indium bromide


Lesson three transition metal compounds
Lesson Three--Transition Metal Compounds form an octet.

Transition metals have electrons in d orbitals and can donate different numbers of electrons, thus giving them several different positive charges.

These can be determined from the Roman numeral which is written next to the metal's name.

Example: Cu1+is Copper I

Pb2+is Lead II

Fe3+is Iron III

Sn4+s Tin IV


Metals with more than 1 charge
Metals with more than 1 charge form an octet.

Examples:

  • Cu + Copper (I)

  • Cu+2 Copper (II)

  • Fe+2 Iron (II)

  • Fe+3 Iron (III)


Practice
Practice form an octet.

  • K and Cl

  • K and S

  • Ca and S

  • Cu (II) and S


Polyatomic ions
Polyatomic Ions!!!!!!!! form an octet.

  • A polyatomic ion is a charged species (ion) composed of two or more atoms covalently bonded.

  • PO4-3 NH4+1


Lewis Dot Structures for Polyatomic ions form an octet.

H +

NH4+ H N H

H


  • Al + PO form an octet.4-3 K + SO4-2

  • Al +3 + PO4-3 K +1 + SO4-2

  • Al(PO4) K2 (SO4)


  • Ca + PO form an octet.4-3

  • Ca +2 + PO4-3

  • Ca3(PO4)2


Covalent bonding notes
Covalent bonding Notes form an octet.

  • Covalent bond: The sharing of a pair of electrons between 2 nonmetal atoms in order to fill its valence shell.

    • Each atom gains 1 electron from each covalent bond it forms with another atom.



Single covalent bonds diatomic molecules
Single Covalent Bonds Diatomic Molecules stable electron configuration and have 8 valence electrons.

Each chlorine needs to gain one electron by sharing electrons each atom achieves stability .

Cl + Cl  Cl Cl

The pair of shared electrons is often represented as a dash. Cl-Cl


Single covalent bonds diatomic molecules1
Single Covalent Bonds Diatomic Molecules stable electron configuration and have 8 valence electrons.

The chlorine atoms only share one pair of valence electrons. The electrons pairs not shared are called unshared electron pairs or lone pairs.

Cl + Cl  Cl Cl


Single covalent bonds in compounds
Single Covalent Bonds in compounds stable electron configuration and have 8 valence electrons.

  • H20 is a molecule containing three atoms with two single covalent bonds.

  • Count up the electrons you have!!!

  • 2 H + O H O H

  • The hydrogen and oxygen attain stable configurations by sharing electrons.


Your turn
Your Turn stable electron configuration and have 8 valence electrons.

  • Example OF2


Double covalent bonds
Double Covalent Bonds stable electron configuration and have 8 valence electrons.

Two pair of electrons are being shared.

S + S  S S


Triple covalent bonds
Triple Covalent Bonds stable electron configuration and have 8 valence electrons.

Three pair of electrons are being shared.

P + P  P P


Charged compounds
Charged Compounds stable electron configuration and have 8 valence electrons.

  • Some compounds do not satisfy their stable configuration and therefore have a charge on the compound.

  • Example- NH4+1


Exceptions to the Octet Rule stable electron configuration and have 8 valence electrons.

The octet rule cannot be satisfied in molecules whose total number of valence electrons is an odd number. However, these molecules do exist in nature.

Examples:

Nitrogen dioxide (NO2)

Boron trifluoride (BF3)

Phosphorus pentachloride (PCl5) = 10 v.e- Expanded octet

Sulfur hexafluroride (SF6) = 12 v.e- Expanded octet


Nonpolar covalent bond
Nonpolar Covalent Bond stable electron configuration and have 8 valence electrons.

  • When atoms bond equally it is considered a nonpolar covalent bond.

  • Cl2

  • O2

  • N2

  • H2


Polar covalent bond
Polar Covalent Bond stable electron configuration and have 8 valence electrons.

  • When electrons are shared unequally it is a polar covalent bond.

  • An atom that strongly attracts electrons is more electronegative and therefore gains a slightly negative charge.

  • The less electronegative atom has a slightly positive charge.

  • This results in a polar bond!


An arrow is used to show which element is donating the unshared pair of electrons.

The crossed end of the arrow indicates a pos. end and the arrow points in the direction of the neg. end

Example:

H-Br


polar molecules are also called dipoles. unshared pair of electrons.

A dipole is a molecule with two partially charged ends or poles.


Examples
Examples unshared pair of electrons.

  • H-Br

  • H2S

  • SCl2

  • CO2


C bond polarity
C. Bond Polarity unshared pair of electrons.

  • Nonpolar Covalent Bond

    • e- are shared equally

    • symmetrical e- density

    • usually identical atoms

C. Johannesson


C bond polarity1

unshared pair of electrons.-

+

C. Bond Polarity

  • Polar Covalent Bond

    • e- are shared unequally

    • asymmetrical e- density

    • results in partial charges (dipole)

C. Johannesson


B lewis structures

unshared pair of electrons.-

+

+

B. Lewis Structures

  • Nonpolar Covalent - no charges

  • Polar Covalent - partial charges

C. Johannesson


A dipole moment

unshared pair of electrons.+

-

H Cl

A. Dipole Moment

  • Direction of the polar bond in a molecule.

  • Arrow points toward the more e-neg atom.

C. Johannesson


B determining molecular polarity

F unshared pair of electrons.

BF3

B

F

F

B. Determining Molecular Polarity

  • Nonpolar Molecules

    • Dipole moments are symmetrical and cancel out.

C. Johannesson


B determining molecular polarity1

O unshared pair of electrons.

net

dipole

moment

H2O

H

H

B. Determining Molecular Polarity

  • Polar Molecules

    • Dipole moments are asymmetrical and don’t cancel .

C. Johannesson


B determining molecular polarity2

H unshared pair of electrons.

net

dipole

moment

CHCl3

Cl

Cl

Cl

B. Determining Molecular Polarity

  • Therefore, polar molecules have...

    • asymmetrical shape (lone pairs) or

    • asymmetrical atoms

C. Johannesson


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