Bonding Quiz

Free Response Questions

GeCl4 SeCl4 ICl4- ICl4

+

1. The species represented above all have the same number of chlorine atoms attached to the central atom.

a) Draw the Lewis structure (electron-dot diagram) of each of the four species. Show all valence electrons in your structures.

b) On the basis of the Lewis structures drawn in part (a), answer the following questions about the particular species indicated.

(i) What is the Cl – Ge – Cl bond angle in GeCl4?

(ii) Is SeCl4 polar? Explain.

(iii) What is the hybridization of the I atom in ICl4-?

(iv) What is the geometric shape formed by the atoms in ICl4+?

2. Answer the following questions that relate to chemical bonding. (a) In the boxes provided, draw the complete Lewis structure (electron-dot diagram) for each of the three molecules represented below.

CF4 PF5 SF5

(b) On the basis of the Lewis structures drawn above, answer the following questions about the particular molecule indicated. (i) What is the F–C–F bond angle in CF4? (ii) What is the hybridization of the valence orbitals of P in PF5? (iii) What is the geometric shape formed by the atoms in SF4?

(c) Two Lewis structures can be drawn for the OPF3 molecule, as shown below.

Structure 1 Structure 2 (i) How many sigma bonds and how many pi bonds are in structure 1 ? (ii) Which one of the two structures best represents a molecule of OPF3? Justify your answer in terms of formal charge.

Answers

1. a) GeCl4

4e- + (4 x 7e-) = 32 e-

SeCl4

6e- + (4 x 7e-) = 34e-

ICl4-

(5 x 7e-) + 1e- = 36e-

ICl4+

(5 x 7e-) – 1e- = 34e-

b) (i) 109.5° sp3 hybridization tetrahedral

(ii) Yes SeCl4 is polar. It is see-saw shaped, has a lone pair, and therefore has a

dipole moment.

(iii) Since the iodine atom has six electron groups, its hybridization is sp3d2. (iv) The see-saw molecular geometry is formed since iodine has five electron groups but one lone pair.

2. a) CF4 PF5 SF5

b) (i) 109.5° sp3 hybridization tetrahedral (ii) 5 electron groups on phosphorus sp3d hybridization (iii) sp3d hybridization no lone pairs trigonal bipyramidal

c) (i) In a single bond, the bond is a sigma bond. In a double bond, the first bond is a sigma bond and the second bond is a pi bond. Therefore, Structure 1 has four sigma bonds and one pi bond. (ii) Structure 2 best represents OPF3. All atoms in Structure 2 have a complete octet, and therefore Structure 2 will be more stable.

Multiple Choice Questions

1. Which of the following species is NOT planar? (A) CO3

2-

(B) NO3-

(C) ClF3

(D) BF3

(E) PCl3

2. The hybridization of the carbon atoms in the molecule represented above can be described as (A) sp (B) sp2

(C) sp3

(D) dsp2

(E) d2sp3

Answers: 1-E, 2-C

1. E-All the other species are planar. However, PCl3 is not planar, but instead is trigonal pyramidal, and has one lone pair.

2. C-Its hybridization is sp3 because there are four bonds to the central atom.

For questions 1-4, select an answer from the five bond types given. You may use a bond type once, more than once, or not at all.

(A) Coordinate covalent bond(B) Covalent bond(C) Hydrogen bond(D) Ionic bond(E) Metallic bond

1. Which is the type of bond responsible the linkage between atoms having a similar electron affinity and high electronegativity?

2. Which is the bond which best accounts for the high melting points and low electrical conductivity of crystalline alkali metal salts?

3. Substances with this bonding have excellent thermal and electrical conductivity.

4. Transitional metal ions form d2sp3 octahedral complexes using this bond type to limit with ligands.

Answers:

1. B-Covalent bonds occur between nonmetals, which are characterized by high electron affinities and high ionization energies.

2. D-Alkali metal salts are made up of cations and anions electrostatically attracted to each other forming a strong crystalline structure. Since the ions cannot move, the salt will not conduct electricity in the solid state.

3. E-In metallic bonding, nuclei are surrounded by a sea of mobile electrons. The electrons’ freedom to move allows them to conduct heat and electricity.

4. A-The transition mal ions are electron-deficient, which allows the acceptance by the central atom of ion-bonded (lone-pair) electrons from ligands.

Things to Know about Bonding

Bonds within Molecules

Ionic Bonds: occurs between atoms of very different electronegativities; they often occur between metals and nonmetals.

Covalent Bonds: two atoms share electrons. Each atom counts shared electrons as part of its valence shell, so both atoms can consider their outer shells complete.

Polarity: one of the atoms (the ore electronegative one) will exert a stronger pull on the electrons in the bond, thus making the molecule dipole (the side of the molecule where the electrons spend more time will be negative and the side where the electrons spend less time will be positive.

Dipole Moment: the polarity of the molecule is measured by its dipole moment. The greater the charge at the ends of the dipole and the greater the distance between the charges, the greater the value of the dipole moment, and the greater the dipole moment, the more polar e molecule is.

Bonds between Molecules—Attractive Forces

Ionic Bonds: ionic solids are held together by the electrostatic attractions between ions that are next to one another in a lattice structure. ionic bonds are strong, and substances that held together by then have high melting and boiling points.

Network (Covalent) Bonds: atoms are held together in a lattice of covalent bonds. They are very hard and have very high melting and boiling points.

Metallic Bonds: group of nuclei surrounded by mobile electrons. Metals are very hard. However, freedom of movement of electrons in metals makes them malleable and ductile. All metals, except mercury, are solids at room temperature and most have high boiling and melting points.

Dipole-Dipole Forces: occurs between neutral, polar molecules. They are relatively weak attractions, and have low melting and boiling points.

London Dispersion Forces: occur between neutral, nonpolar molecules. These very weak attractions occur because of the random motions of electrons on atoms within molecules. So among substances that experience only London dispersion forces, the one with more electrons will generally have higher melting and boiling points.

Hydrogen Bonds: the positively charged hydrogen end of a molecule is attracted to the negatively charged end of another molecule containing an extremely electronegative element. Hydrogen bonds are much stronger than dipole-dipole forces because when a hydrogen atom gives up its lone electron to a bond, its positively charged nucleus is left virtually unshielded.

Molecular Geometry

Tetrahedral Bubbles

Things you need:

- cubes of potatoes (about 1 centimeter cubes)- toothpicks- a 1-liter beaker of soapy solution (a little bit if dishwashing soap in water)

Directions:

1. Using the potato cubes and toothpicks, make a tetrahedron. To make it, use six toothpicks and four potato cubes. It should be a four-sided figure.

2. Use one more toothpick as a handle, and dip the tetrahedron model into the 1-liter beaker of soapy water.

3. The result should be a tetrahedral bubble.

4. After completing the experiment, throw everything away.

Goal:

-The experiment makes the point that a tetrahedral molecule has atoms that point to the corners of s tetrahedron.