UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to...
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Transcript of UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to...
![Page 1: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/1.jpg)
UNIT 7: BONDING
![Page 2: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/2.jpg)
Why Bond?
Elements bond in order to get a full valence shell
Elements want to have the same number of electrons as the noble gases The Octet Rule: in forming compounds,
atoms tend to achieve the electron configuration of a noble gas
**** only VALENCE electrons are involved in bonding
![Page 3: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/3.jpg)
Types of Bonds
Ionic Covalent Metallic
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Review of Metals
Metals lose electrons to form positive ions (cations)
Ionic radius is smaller than atomic radius
Group 1: Alkali metals Lose 1 electron
Group 2: Alkaline Earth Lose 2 electrons
![Page 5: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/5.jpg)
Review of Nonmetals
Gain electrons to form negative ions (anions)
Ionic radius is larger than atomic radius
Group 17: Halogens Gain 1 electron
Group 16: Chalcogens Gain 2 electrons
![Page 6: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/6.jpg)
Ionic Bonds
The force of attraction that holds ions of opposite charge together This attraction is between a metal and a
nonmetal Forms from the TRANSFER of electrons
Electrons are transferred from METAL NONMETAL
Large difference in electronegativity Overall charge of compound is neutral (+
and – cancel out) Ex) NaCl
![Page 7: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/7.jpg)
Animation
http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/bom1s2_11.swf
![Page 8: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/8.jpg)
Writing Lewis Dot Structures for Ionic Compounds
Lewis Dot diagrams help us visualize what is happening to valence electrons when a bond forms
Remember- Follow the octet rule!! Ex) Li and F
Steps: 1) Draw all elements and their individual Lewis Dot diagrams. 2) Draw an arrow indicating the transfer of electrons3) Redraw your bonded compound with appropriate charges
![Page 9: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/9.jpg)
More Practice…
Draw the Lewis Dot Diagrams for the following ionic compounds:
BaO
K2S
CaCl2
![Page 10: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/10.jpg)
What if you are not given the formula?
Draw the Lewis Dot diagram for the ionic bonding between sodium and sulfur.
![Page 11: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/11.jpg)
Ionic Compounds
An ionic compound exists as a collection of positively and negatively charged ions arranged in repeating patterns
A formula unit is the lowest whole-number ratio of ions in an ionic compound NaCl (1:1 ratio) , MgCl2 (1:2 ratio)
![Page 12: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/12.jpg)
Properties of Ionic Compounds (salts)
Ionic bonds are the strongest bonds, so all are solids
Hard High melting points and boiling points Soluble in water Cannot conduct electricity as a solid Can conduct electricity as a liquid or in
an aqueous solution http://www.youtube.com/watch?v=NfNIn4R8tg4
They are electrolytes- substances that conduct electricity when dissolved in water
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Covalent Bonds
A bond between two nonmetals that involves a sharing of electrons (“tug of war”) Can have EQUAL or UNEQUAL
sharing Small or no difference in
electronegativity Overall charge of a covalent
compound is neutral Covalent compounds are called
molecules Ex) O2, CO, CCl4, H2
![Page 14: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/14.jpg)
Types of Covalent Bonds
There are 3 types of covalent bonds
Covalent Bonds
Non-Polar Covalent
Polar covalen
t
Coordinate Covalent
![Page 15: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/15.jpg)
Non-Polar Covalent Bond
Electrons are shared equally Same atoms- same
electronegativity All diatomics have non-polar bonds! Remember: HOFBrINCl
Two of the same non-metal
Ex) Br2
![Page 16: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/16.jpg)
Polar Covalent Bond
Electrons are shared unequally Different atoms with different
electronegativity values Ex) HF
The more electronegative atom attracts electrons more strongly and gains a slightly (-) charge
The less electronegative atom has a slightly (+) charge
![Page 17: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/17.jpg)
Bond Polarity
• Bond Polarity: refers to a separation of charge in a bond
Ex) HF : partial (+) charge on H and partial (-) charge on F
• This separation of charge is often called a dipole
• ***The greater the difference in electronegativity, the greater the polarity.
![Page 18: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/18.jpg)
Challenge Question
Which of the following covalent compounds has the greatest degree of polarity?
Choice 1) CO
Choice 2) HCl
Choice 3) NO
Choice 4) HBr
![Page 19: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/19.jpg)
Drawing Lewis Structures for Covalent Compounds
Remember! After drawing your diagram, all atoms MUST have 8 valence electrons (except for hydrogen, which should have 2 electrons)
Ex) F2
![Page 20: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/20.jpg)
What if we have more than two non-metals?
Ex) H2O
Ex) NH3
![Page 21: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/21.jpg)
Lewis Structures Continued…
When elements from Group 14 are involved in a covalent bond, they spread their e- out
Carbon tends to form 4 covalent bonds
Ex) CH4
Ex) CCl4
![Page 22: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/22.jpg)
Practice Problem
Draw the Lewis Structure for CH3Br
![Page 23: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/23.jpg)
Can you have more than one bond?
Yes! So far all we have seen are single covalent bonds in which one pair of electrons is shared
Double covalent bond: a bond between two atoms where 2 pairs of e- are shared
Ex) O and O
*** Oxygen tends to form 2 bonds! Triple covalent bond: a bond between two
atoms where 3 pairs of e- are sharedEx) N and N
*** Nitrogen tends to form 3 bonds!
![Page 24: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/24.jpg)
More Practice with Lewis Diagrams..Draw the Lewis diagrams for CO2
![Page 25: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/25.jpg)
Challenge Problem
Draw the Lewis Structure for HCN
![Page 26: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/26.jpg)
Let’s Summarize
C, H, O and N form how many bonds??
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Coordinate Covalent Bond
A bond in which both electrons of the shared pair come from the same atom
Ex) NH4+
![Page 28: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/28.jpg)
VSEPR Geometry
Lewis Dot diagrams fail to show the 3-dimensional shapes of molecules
VSEPR Theory (Valence-Shell Electron Pair Repulsion Theory) Repulsion between e- pairs causes
molecular shapes to adjust so that valence e- pairs stay as far apart as possible
http://phet.colorado.edu/en/simulation/molecule-shapes
![Page 29: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/29.jpg)
Molecular Polarity
Molecular polarity is different from bond polarity!!
http://phet.colorado.edu/en/simulation/molecule-polarity In a non-polar molecule, electron
distribution is even (symmetrical) In a polar molecule, electron distribution
is uneven (asymmetrical)
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Intermolecular Forces (IMFs)
Only between covalent molecules, never ionic compounds
Weak forces that act between molecules and hold
molecules to each other ****IMFs are not bonds!!!
IMFs occur BETWEEN molecules, bonding occurs WITHIN molecules
![Page 31: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/31.jpg)
IMFs vs. Bonds
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Intermolecular Forces of Attraction
• Van der Waals Forces• Dipole interactions• Hydrogen Bonds
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London Dispersion Forces
London Dispersion forces: weakest of all molecular interactions; caused by temporary shifts in charge
- Between nonpolar molecules http://antoine.frostburg.edu/chem/senese/101/liquids/faq/h-bonding-vs-london-forces.shtml
- The bigger the atom or molecule the greater the strength of dispersion forces the higher the BP
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Think about it…
Which has the strongest London dispersion forces?
F2
Cl2
Br2
I2
![Page 35: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/35.jpg)
Dipole-Dipole Interactions
Dipole interactions: attraction between polar molecules
The positive and negative charges of different molecules attract each other
Ex. HCl http://chemmovies.unl.edu/ChemAnime/DIPOLED/DIPOLED.html
![Page 36: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/36.jpg)
Hydrogen bonds: A special case of dipole-dipole interactions
Hydrogen bonds: intermolecular force between the H of one molecule and a highly electronegative atom of another molecule (must be N, O, or F)
Ex. H2O, NH3
***The high b.p. of water is due to hydrogen bonding
![Page 37: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/37.jpg)
Molecule-Ion Attraction
Partial charges on a molecule are attracted to ions
This is what happens when NaCl dissolves in water
Picture: The hydrogens of water align themselves
towards the anion and the oxygen align themselves towards the cation
http://www.kentchemistry.com/links/bonding/LikeDissolveslike.htm
![Page 38: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/38.jpg)
Molecule-Ion Attraction
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Properties of Covalent Compounds Soft Low melting points and boiling
points Cannot conduct electricity in any
phase Generally insoluble in water
Except sugars! (C12H22O11)
![Page 40: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/40.jpg)
Network Solids
A special case of covalent bonding Atoms held together in a very strong covalent
network Ex. Carbon (Diamond) and SiO2 Properties:
Hard High m.p. and b.p. Poor conductors
![Page 41: UNIT 7: BONDING. Why Bond? Elements bond in order to get a full valence shell Elements want to have the same number of electrons as the noble gases.](https://reader035.fdocuments.us/reader035/viewer/2022081507/551ab094550346b2288b49ee/html5/thumbnails/41.jpg)
Holds metals together Electrons are mobile and move from one
atom to another, creating (+) charged metal ions
Charged metal ions are immersed in a “sea of mobile electrons”
Metallic Bonding
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Bond Energy
Bonds do not break and form spontaneously- an energy change is required
When a bond is broken, energy is ABSORBED (required) Ex) F2 (g) + ENERGY F (g) + F (g) The greater the # of bonds between
atoms, the more energy you need to break them
When a bond is formed, energy is RELEASED (given off) Ex) F(g) + F(g) F2 (g) + ENERGY