Aimee Saitta
12/23/97
Period 5
Discussion Questions
1. When given a linear molecule I determined its overall structure to be polar. The electron distribution in that molecule is described as unequally shared valence electrons.
2. H2O is an example of a linear molecule from the lab that demonstrates what I have described in question number one. This molecule contain one central atom.
3. When given a linear molecule I determined its overall structure to be nonpolar. The electron distribution in that molecule is described as equally shared valence electrons.
4. CO2 and C2H2 are examples of linear molecules from the lab that demonstrates what I have described in question number three. Each of these molecule contains at least one central atom.
5. Electronegativity and molecular shape are the two factors that determine whether or not a given molecule in polar of nonpolar in overall character. Electronegativity differences of 0 to 0.4 are considered nonpolar covalent bonds, greater than 0.4 to 1.7 are considered polar covalent bonds and greater than 1.7 are considered ionic bonds.
6. It is possible for a given molecule to contain individual bonds that are polar ( 0.5) in nature, yet the overall molecule is said to be nonpolar because they are symmetrical.
7. CCl4 and SiCl4 are examples of nonlinear molecules that demonstrated the ideas presented in question number six. Each nonlinear molecule contains only one central atom. The geometric shape of both nonlinear molecules is tetrahedral.
8.
a.) The geometric structure for molecules such as SF2 and NH3 is different from what I would expect by simply looking at their respective Lewis Structures because the angles are decreased because the unshared electron pairs repel electrons more strongly than bonding electron pairs. The geometric shape of SF2 is linear and the geometric shape of NH3 is triangular planar. This happens because of lone pairs of electrons.
b.) The geometric shape of such a molecule as a result of this difference is it becomes bent shape.
9. In terms of overall covalent character for a given molecule the type of conclusion I can make based on those molecules which contain unbonded pairs of electrons on their central atom compared to molecules whose central atom lacks unbonded electron pairs is if the central atom is not completely paired it bent.
10.
a.) List of molecules containing two central carbon atoms, arranged in order of decreasing polarity.
(1) CH3CO2H (4) C2HCl (7) C2H4
(2) CH3CH2OH (5) C2Cl2 (8) C2H6
(3) CH3CH2Cl (6) C2H2
b.) The criteria I used to choose the molecule I listed first as the most polar over its next competitor was the electronegativity difference between C-O and the double bonds which bonded the C to the O in its molecular shape.
c.) The criteria I used to choose the molecule listed last as the least polar, or most nonpolar molecule, over its next competitor was symmetrical and no multiple bonds, thus not as much electron concentration between the two central carbon atoms.
11.
a.) Molecules of O2 and N2 both demonstrate nonpolar covalent bond characters.
b.) Looking at the individual atoms that make up each of these molecules, these molecules have a particular type of covalent character because there is no difference in their electronegative values. This is know as a diatomic molecule, atoms of the same element bonded together with no difference in their electronegative values.
c.) Although these two molecules lack a central atom, they contain a linear geometric shape and this geometry helps to impart this type of covalent bond because it is symmetrical.
12.
a.) C2Cl2 = nonpolar C2HCl = polar
b.) Both of the above molecules are like O2 and N2 because they are both linear and there are multiple bonds in all of the molecules mentioned.
c.) C2HCl is polar and C2Cl2 is not because in the C2HCl molecule the electronegativity between C and Cl makes it a polar bond. On the other side of the molecule the C and H bond is nonpolar. There is an unequal distribution of electrons in this molecule.
13. Intermolecular forces are the forces of attraction between molecules.
14. A common method of comparing the intermolecular forces for two compounds both in the same physical form is by comparing their boiling points.
15.
a.) If I were given equal amounts of C2Cl2 and C2HCl, both in the same physical form of matter, C2HCl would be harder to undergo a physical change.
b.) This is because C2Cl2 is more polar, plus C2Cl2 it is smaller and less complex molecule than C2HCl. For these reasons C2Cl2 would be harder to undergo a physical change.
c.) This is a 3-D structural formula showing how two molecules of the most strongly held compound would interact.
16.
a.) If I were given equal amounts of CH3CH2OH and H2O, both in the same physical form, H2O would be harder to undergo a physical change.
b.) This is because H2O is a dipole molecule in which the centers of positive and negative charge do not coincide. One end of the H2O molecule is somewhat positive and the other end is negative.
c.) These are two 3-D structural formulas illustrating my explanation to part b. Both pictures show how two identical molecules of each compound interact with each other.
d.) The two things both of these compounds or molecules have in common are they are both polar covalent molecules and they polar have a particularly strong type of dipole force that is only found in certain polar covalent molecules.
17. It is possible for various elements to join together to form compounds because of bond length and bond energy. Bond length is the average distance between two bonded atom and bond energy is the energy required to break a chemical bond and form neutral atoms.
18. Hybridization must occur when forming a particular molecule because it gives new orbitals equal energies, so to ensure the strongest bonds possible for the central atoms orbitals of equal shape and energy. Hybridization makes this happen by mixing atomic orbitals to form new orbitals of equal energies.
19. Using the creation of CH4 from 1 atom of C and 4 atoms of H, a specific example of hybridization would be one s and three p orbitals combined to give four sp3 hybrid orbitals. Hybrid orbitals are at an energy level in between the levels of the orbitals that have combined.
20.
a.) Using the ideas from both theories of molecular geometry, VESPR and hybridization, VESPR is the theory that has to do with determining the proper bond angles for a given molecule. The electrostatic repulsion between the valence level electron pairs surrounding an atom which causes these pairs to be as far apart as possible.
b.) I am given a molecule whose central atom lacks an unbonded electron pairs and has formed bonds with three additional atoms. The proper geometric shape for this molecule is triangular planar, the bond angles between the atoms involved are 120 degrees and the appropriate orbitals that are formed during bond formation are triangular planar geometry.
120
c.) Given molecules NH3 and CH4, the proper bond angles for each molecule would be NH3 with bond angles of 107 degrees and CH4 with bond angles of 109.5 degrees. There is a difference between them because there are more atoms present therefore there is less space, there is more repulsion between them.
107 109.5