FAIR USE STATEMENT: Please feel free to edit and use this presentation in your classroom. Please do not remove the credit line on the title page or republish the file in whole or in part as your own. Please do not distribute the file to individuals or at conferences or workshops. I am more than willing to share the presentation with anyone that contacts me at rhondaa@cox-internet.com. The images in the presentation are not original and therefore the presentation is distributed freely and only for classroom instruction. Rhonda Alexander

Rhonda Alexander 2002Robert E. Lee High School, Tyler, TX

Next why bonds

General•All bonding forces are due to electrostatic charge. Opposite charges attract, Like charges repel.

This diagram shows the attraction and repulsion between atoms: The outer ring (e-) is the electron cloud. The inner red ring is the nucleus.

Next forming H2 bond movie

ElectronegatElectronegativity ivity DifferenceDifference

0.00.000

0.60.655

0.90.944

1.11.199

1.41.433

1.61.677

1.91.911

2.12.199

2.52.544

3.03.033

Percent Percent Ionic Ionic CharacterCharacter

0%0% 1010%%

2020%%

3030%%

4040%%

5050%%

6060%%

7070%%

8080%%

90%90%

Percent Percent Covalent Covalent CharacterCharacter

100100%%

9090%%

8080%%

7070%%

6060%%

5050%%

4040%%

3030%%

2020%%

10%10%

0 to .40 .40 to 1.67 1.67 and greater

Difference in Electronegativity

IONICPOLAR COVALENT

NONPOLARCOVALENT

Trends in electronegativityTrends in electronegativityIncreases right because Zeff increases, which attracts electrons more strongly.

Outermost electrons are in same shell (same n).

Increases because as you go up

valence electrons arecloser to the nucleus(orbitals are smaller)

so they are morestrongly attracted

to the atom.

PracticePractice Rank these elements by Rank these elements by

electronegativity:electronegativity:

Co, O, Si, SrCo, O, Si, Sr

PracticePractice Rank these elements by Rank these elements by

electronegativity:electronegativity:

least = Sr < Co < Si < O = most least = Sr < Co < Si < O = most electronegative electronegative Increase

Incr

ease

Next types

THREE TYPES OF BONDS

Next type

Next metallic

•Metallic bonding can be pictured as positive metal ions in a sea of freely-moving negative electrons (delocalized electrons)•Metallic bonding is moderate to strong•Occurs between metal atoms.

Metallic bond

Next ionic

Ionic bondIonic bond

An ionic bond may result from electron An ionic bond may result from electron transfertransfer

In an ionic bond, electrons are not In an ionic bond, electrons are not shared. shared.

Atoms are held together by Atoms are held together by electrostatic attraction between electrostatic attraction between positive and negative ions.positive and negative ions.

Na F

··

····

· ·+ ·· F

··

····Na+

–

Next lattice energy

Next Coulomb’s law

Shared electrons are in the outer Shared electrons are in the outer shells of shells of bothboth atoms atoms

The valence (outer) shells of The valence (outer) shells of bothboth of of these H atoms now have 2 electrons.these H atoms now have 2 electrons.

Covalent bondCovalent bond

··H H

Next covalent

Next polarity

POLAR COVALENT

NONPOLAR COVALENT

Next polarity

Next bond type Next bond type practicepractice

PracticePractice Referring Referring onlyonly to a periodic table to a periodic table, classify these bonds as , classify these bonds as

ionic, polar covalent or nonpolar covalentionic, polar covalent or nonpolar covalent S–SS–S N–FN–F Sn–SiSn–Si Mg–O Mg–O Si–PSi–P Ni–SNi–S C-HC-H Cs–FCs–F

Next $ %

Polar covalent bondsPolar covalent bonds

More electronegativepartial negative charge

Less electronegativepartial positive charge

··–F

··

··

H+

Next bonding pairs

Covalent bondCovalent bond Bonding electron pairs form the bondBonding electron pairs form the bond Nonbonding electron pairs are called Nonbonding electron pairs are called

lone pairslone pairs

·· F F

··

····

····

· ·+

·· F

··

······ F

····

–

F

········ F

····

or

Next multiple

Multiple bonds Multiple bonds Atoms can share more than two electronsAtoms can share more than two electrons

single bondsingle bond FF22

double bonddouble bond OO22

triple bondtriple bond NN22

O=O

··

····

··

···· NN

–

F··

······ F

····

Next strength

Multiple bonds are fatter Multiple bonds are fatter and strongerand stronger

NN22 O O22 F F22triple bondtriple bond double bonddouble bond single single

bondbond

Next