CHEMICAL BONDING - PowerPoint PPT Presentation

1 / 33
About This Presentation
Title:

CHEMICAL BONDING

Description:

CHEMICAL BONDING Cocaine * To play the ... Review of Chemical Bonds There are 3 forms of bonding: ... MOLECULAR GEOMETRY Some Common Geometries Linear Trigonal Planar ... – PowerPoint PPT presentation

Number of Views:247
Avg rating:3.0/5.0
Slides: 34
Provided by: NeilR193
Category:

less

Transcript and Presenter's Notes

Title: CHEMICAL BONDING


1
CHEMICAL BONDING
  • Cocaine

2
Chemical Bonding
  • What property of atoms determines the type of
    bond they form?

3
Review of Chemical Bonds
  • There are 3 forms of bonding
  • _________complete transfer of 1 or more
    electrons from one atom to another (one loses,
    the other gains) forming oppositely charged ions
    that attract one another
  • _________some valence electrons shared between
    atoms
  • _________ holds atoms of a metal together

Most bonds are somewhere in between pure ionic
and pure covalent.
4
Electronegativity
  • How do you determine what type of bond is formed
    between two atoms?
  • Look at the electronegativity values of the
    atoms.
  • Electronegativity-the ability of an atom to
    attract electrons in a chemical bond.

5
The type of bond can usually be calculated by
finding the difference in electronegativity of
the two atoms that are going together. In
general, the farther apart 2 atoms are on the
periodic table, the more polar the bond they make
will be.
6
Electronegativity Difference
  • If the difference in electronegativities is
    between
  • 1.7 to 4.0 Ionic
  • 0.4 to 1.7 Polar Covalent
  • 0.0 to 0.4 Non-Polar Covalent

Example NaCl Na 0.8, Cl 3.0 Difference is
2.2, so this is an ionic bond!
7
Non Polar Bonds
  • Diatomic Elements
  • Br2 I2 N2 Cl2 H2 O2 F2
  • These elements do NOT exist as single atoms on
    their own.
  • MEMORIZE THESE!
  • Since the two atoms in a diatomic molecule have
    identical electronegativities,
  • ?EN 0 and the bond is nonpolar covalent.
  • If the difference in electronegativity is between
    0 - 0.4, the bond is nonpolar covalent.
  • What type of compounds have nonpolar covalent
    bonds?

8
Bond Polarity
?EN ENCl - ENH ?EN 3.0 2.1 ?EN 0.9
(polar covalent)
  • HCl is POLAR because it has a positive end and a
    negative end. (difference in electronegativity is
    between 0.4 and 1.7)

Cl has a greater share in bonding electrons than
does H.
Cl has partial negative charge (-d) and H has
partial positive charge ( d)
9
NONPOLAR COVALENT
  • Nonpolar A bond in which a pair of electrons is
    distributed or shared equally between two atoms

10
NONPOLAR COVALENT
  • Completely non-polar
  • Mostly non-polar
  • Nitrogen gas (N2), methane gas (CH4), oxygen gas
    (O2), chlorine gas (Cl2) (and homogeneous
    diatomic molecules such Br2, I2, and F2),
    acetylene (C2H2), carbon tetrachloride (CCl4).
  • Note that these are all perfectly symmetrical and
    this is why they are non-polar. The dipole
    moments of any polar bonds is completely canceled
    out by equal and opposite dipole moments from the
    other bonds.
  • All basic hydrocarbons (such as propane, butane,
    pentane, hexane, cyclohexane, octane and others),
    oils (such as vegetable oils), fats and greases,
    gasoline, diethyl ether, and others

11
Examples
  • Predict the bond type in
  • HCl
  • NaCl
  • CCl4
  • NH3

12
Dipoles
  • Molecules that have a polar covalent character
    are said to have a dipole
  • The more electronegative element pulls electrons
    and makes that side of the molecule more
    negative.
  • Use an arrow to indicate the direction electrons
    are being pulled.

13
(No Transcript)
14
Bond Polarity
  • Like Dissolves Like
  • Polar dissolves Polar
  • Nonpolar dissolves Nonpolar

15
Bond Polarity
  • This is why oil and water will not mix! Oil is
    nonpolar, and water is polar.
  • The two will repel each other, and so you can not
    dissolve one in the other

16
Types of intermolecular forces
  • Induced dipole or dispersion forces
  • Large covalent molecule shifts e- to make ?- and
    ? and those charges are attracted
  • Usually non-polar

17
Types of intermolecular forces continued
  • Dipole-dipole force attraction between polar
    molecules
  • Stronger than induced dipole
  • Hydrogen bonding strongest type of
    intermolecular force
  • hydrogen of 1 atom attracted to F,O,N of another
    atom

18
In Conclusion
  • Intermolecular forces
  • Hydrogen bond
  • Strongest bond, so higher MP and BP
  • Dipole-dipole
  • Medium, so medium MP, BP
  • Induced dipole (dispersion forces)
  • Low MP, BP
  • The longer the C chain the higher the MP and BP

19
Last Fridays Lab(some molecular compound info
that might help)
20
-Cottonseed oil is a mixture of multiple
different molecular compounds.
-Cola check the ingredients and nutrition facts.
-Mineral oil contains hydrocarbons (molecular
compounds) that are byproducts of petroleum
distillation.
21
This comparison may help you with your lab
  • Ionic Bonds
  • Formula unit
  • Transfer e-
  • Cation and anion
  • Solid
  • High Solubility in water
  • High BP, MP gt300C
  • Good conductor in solution
  • Covalent bonds
  • Molecule
  • Share e-
  • Nonmetals
  • Solid, liquid or gas
  • Low solubility in water
  • High to Low MP, BPlt300C
  • Poor to non-conductivity

22
What is an acid?
  • An acid is a molecular substance that dissolves
    in water to produce hydrogen ions
  • NOTE ALL acids contain hydrogen BUTNot
    everything with hydrogen is an acid!
  • They are covalent compounds that separate into a
    cation and an anion in water (ionic tendency)

23
Naming Acids
  • Binary acids
  • The name begins with the prefix hydro-
  • The name is derived from the anion
  • The suffix ide should be changed to ic

24
Try two for yourself
  • One of the many uses for HCl is cleaning
    concrete, but its also found in your
    stomachWhat is the name of this acid?
  • Some wheel cleaning compounds used in carwashes
    contain hydrofluoric acid. What is the formula
    for this acid?

25
Naming Acids
  • Polyatomic acids
  • Do not use prefix hydro-
  • The suffix ate should be changed to ic
  • The suffix ite should be changed to ous

He -ate -ic and got stomach -ite -ous.
26
(No Transcript)
27
Dont worry, these problems wont corrode your
brain
  • In addition to its many other uses, nitric acid
    is commonly used in the woodworking industry to
    artificially age pine and maple. What is the
    formula for this acid?
  • What would be the name of HClO2
  • H2CrO4 was once widely used in the band
    instrument repair industry, because of its
    ability to birghten raw brass. What is the
    name of this acid?

28
MOLECULAR GEOMETRY
29
MOLECULAR GEOMETRY
Molecule adopts the shape that minimizes the
electron pair repulsions.
  • VSEPR
  • Valence Shell Electron Pair Repulsion theory.
  • Most important factor in determining geometry is
    relative repulsion between electron pairs.

30
Some Common Geometries
Linear
Tetrahedral
Trigonal Planar
31
VSEPR charts
  • Use the Lewis structure to determine the geometry
    of the molecule
  • Electron arrangement establishes the bond angles
  • Molecule takes the shape of that portion of the
    electron arrangement
  • Charts look at the CENTRAL atom for all data!
  • Think REGIONS OF ELECTRON DENSITY rather than
    bonds (for instance, a double bond would only be
    1 region)

32
Structure Determination by VSEPR
  • Water, H2O

The electron pair geometry is TETRAHEDRAL
2 bond pairs 2 lone pairs
The molecular geometry is BENT.
33
Balloon Activity
Write a Comment
User Comments (0)
About PowerShow.com