BondIONIC/COVALENT BONDING AND MOLECULAR GEOMETRY
BONDING AND MOLECULAR GEOMETRY Kris Kleeman ovided by the Institute of Museum and Library BONDING and MOLECULAR GEOMETRY Time Frame3 Contents Checklist Demonstrations Electronegativity Worksheet Comparing Ionic and Covalent Bonds Lab Molecular Model Lab ience or chemistry classes in grades 9-12.Define chemical bond.Relate chemical bond formatiDescribe the formation of positive and negative ions.Describe the formation of chemical bonds.
Account for the physical and chemiDescribe metallic bonds.Explain the physical and chemical properties of metallic bonds.
atoms that bond covalently.Describe the formation of single, nd identify resonance structures.Identify exceptions to the octet rule.
Predict the shape of a molecule.Compare ad contrast polar, compounds that are covalently bonded.Describe the structure and shape of a water molecule.ths of intermolecular forces.Describe how the formation of a hydrogen bond.
Illinois Learning Standards and Benchmarks: State Goal 11:
Understand the processes of scientific inquiry and technological design to investigate questions, conduct experiments and solve problems.
LEARNING STANDARD A: Know and apply the concepts, principles, and processes of
SCIENCE PERFORMANCE DESCRIPTORS 11.A.3
Stage I -Conduct inquiry investigation, using technologies for observing and measuring directly, indirectly, or remotely.
State Goal 12:
Understand the fundamental concepts, principles and interconnections of the life, physical and earth/space sciences.LEARNING STANDARD C: Know and apply concepts that describe properties of matter and energy and the interactions between them.
Analyze the properties of materials (eg.mass, boiling point, melting point, hardness) in relation to their physical and/or chemical structures.SCIENCE PERFOMRANCE DESCRIPTORS 12.C.3
Investigate the atomic and nuclear structure of matter, predicting bonding and molecular structure.
Explain how physical and chemical structure of matter affect its properties relating to bonding types and shapes of molecules to organic and inorganic compounds.12.C.1
Explain chemical bonding reactions referencing bonding potential and strengths within and between atoms and molecules.
State Goal 13: Understand the relationships among science, technology, and society in historical and contemporary contexts.
LEARNING STANDARD A: Know and apply accepted practices of science.
SCIENCE PERFORMANCE DESCRIPTORS 13.A.1
Stage H& I
Apply appropriate principles of safety within and beyond the science classroom.
electrons, Bond with a Work sheet Day 2-3:
Comparing Types of Bonds Day 3:
Comparing Formal Built Models
Intermolecular Forces Water Tension, Drops of Water on a Penny, Ice Model, Salt
Model List of Activities Labs- Models of Covalent Compounds,
Comparing Ionic and Covalent Bonds Demonstrations
ADDITIONAL ITEMS NEEDED OUTSIDE MATERIALS NEEDED: 100 ml Beakers
Watch glasses Lab Burners
Scoopulas Potassium Iodide Potassium Chloride Camphor Sodium Chloride DEMONSTRATIONSPetri Dishes Buttermilk Water eets and exercises to enhance the Chemical Bonding:
The Ties ThatChemical Education.Water Word Search Journal of Chemical Education.2005, 82, www.Flinnscientific.comrength of Intermolecular Forces 12
Student Model Kits 1
Ice structure model 1
Salt structure model isolated & neutral atoms rarely exist in nature elements form compounds to complete an octet in their outer energy level
Chemical Bond: link between atoms that results in the attraction of e- by the nuclei of the atoms.
bonds that transfer e- from one atom to another
must have a donator & receiver.** is always exothermic
IONIC STRUCTURES - NaCl B.COVALENT BOND- bond that results from the sharing of electrons.1.
equal sharing a.Are symmetrical 2.
unequal sharing a.Are asymmetrical 3.Produce molecules 4.Unshared e- are called lone pairs **Usually
exothermic, sometimes endothermic
The most electronegative element will attract the e- more, creating a partial (-) and partial (+) charge differential
.- sharing 3 pair = triple strong variable HardnessCovalent Compounds Worksheet - Key
low Conductivity only in
Liquid state Melting Pt moderate to Solubility
polar solvents low
insoluble Draw a skeleton and distribute the shared e-
in free atom
LONDON DISPERSON FORCES/VAN DER
attraction of H and unshared e- on another electronegative element
accounts for high boiling pt of H containing cmpds
strongest type of bond in nature- capable of absorbing a lot of energy.
* COHESION * ADHESION
STRUCTURE: Bent, Covalent, Polar, Hydrogen bonded - form molecular grouping of 6-9 molecules - rigid solid structure - hexagonal
PROPERTIES: due to H-bonding
high specific heat
high melting point
high boiling point
high surface tension
Lewis (Electron) Dot Diagrams valence electrons for each atom, then total those needed 3 H need 2 electrons each 3*2 = 6
1 N needs 8 electrons
1*8 = 8
14 electrons needed .
If molecule is charged, add an electron for
each negative charge, subtract an electron for each positive charge.
3 H have 1 valence electron each 3*1 = 3
1 N has 5 valence electrons
1*5 = 5
8 electrons available.
and electrons available:
Bonds = bonding electrons/2
14 electrons needed
Covalent compounds worksheet answers
1) Based on the properties of the following materials, determine whether they are made of primarily ionic compounds or covalent compounds:
a) telephone receiver:
d) candy corn:
2) Name the following covalent compounds:
hydrogen bromide (or hydrobromic acid)
3) Write the formulas for the following covalent compounds:
a) diboron hexahydride
b) nitrogen tribromide
c) sulfur hexachloride
d) diphosphorus pentoxide
4) Write the empirical formulas for the following compounds:
b) boron trichloride
5) List three differences between ionic and covalent compounds: Ionic compounds are hard, covalent compounds are not.
Ionic compounds are brittle, covalent compounds are not.
Ionic compounds have a high melting and boiling point, covalent compounds have a low melting and boiling point.
Ionic compounds involve the transfer of electrons, while covalent compounds share electrons.
Ionic compounds conduct electricity when dissolved in water, covalent compounds dont.6) Explain why ionic compounds are formed when a metal bonds with a nonmetal but covalent compounds are formed when two nonmetals bond.
When a metal bonds with a nonmetal, electrons are transferred from the metal to the nonmetal because metals have very low electronegativities and nonmetals have high nonmetals tend to have similarly high electronegativities, neither atom can take electrons from the other, forcing them to share electrons.
7) What are the shapes of the following molecules?
a) carbon disulfide
b) boron trifluoride
c) carbon tetrafluoride
8) What does electronegativity have to do with bond polarity?
The greater the difference in electronegativity between two covalently bonded atoms, the more polar the bond.
9) Explain how hydrogen bonding takes place.
Because hydrogen has a low electronegativity, it forms polar bonds with electronegative atoms and has a partial positive charge.
When atoms with lone pairs of electrons are nearby, they tend to donate electron density from the lone pair toward the hydrogen to help stabilize it.
This causes the molecules to stick to one another because of the attraction of partially positive and negative charges.
10) Why is the bond length of nitrogen much shorter than the bond length of chlorine?
Nitrogen, N2, has a triple bond, while chlorine, Cl2, is singly bonded.
Generally, multiple bonds are shorter than single bonds because the atoms are held more tightly together.
11) What is an organic compound?
Organic compounds contain carbon.
Most contain hydrogen, and many contain oxygen, nitrogen, and sulfur..