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Name Date Due Pre-AP: Covalent Bonding and Nomenclature Unit Homework

Directions: Write your answers to the following questions in the space provided. For problem solving, show all of your work and write your final answer on the blank line.

Part A 1. What is a ? A chemical bond is a strong attractive between or ions in a compound. 2. Why do atoms form chemical bonds? Atoms form chemical bonds in order to decrease potential and create more stable arrangements of matter. 3. What distinguishes an ionic bond from a ? In an ionic bond, valence electrons are transferred between atoms. In a covalent bond, valence electrons are shared by the atoms. 4. What distinguishes a polar covalent bond from a nonpolar covalent bond? In a polar covalent bond, the electrons are shared unequally. In a nonpolar covalent bond, the electrons are shared equally.

5. What is a ? What type of bond produces a dipole? A dipole is a bond formed when the atoms in a chemical bond are not sharing the electrons equally. Polar covalent bonds contain a dipole. 6. How can you identify the negative and positive in a polar covalent bond? The negative dipole is formed by the with the higher electronegativity. The positive dipole is formed by the atom with the lower electronegativity. 7. According to the general rules of electronegativities, what type of bond is formed by each of the following pairs of elements? If the bond is polar covalent, identify the negative dipole (δ-) and the positive dipole (δ+). a. potassium and ionic

b. sulfur and sulfur nonpolar covalent + - c. and p olar covalent, C = δ , Br = δ

d. zinc and ionic

8. Order the following covalent bonds from least to most polar. a. H – Cl ΔEN = 0.9 b. H – Br ΔEN = 0.7 c. H – Se ΔEN = 0.3 e, c, d, b, a d. H – C ΔEN = 0.4 e. F – F ΔEN = 0.0

1 9. What type of bond do nonmetals generally form with other nonmetals? They generally form covalent bonds.

10. What type of bond is generally formed between the alkali metals and the halogens? They generally form ionic bonds.

11. What type of bond is generally formed between the halogens and the oxygen group?

They generally form polar covalent bonds. Part B

12. Draw the Lewis dot representations for each of the following neutral atoms:

a. sodium Na e.

b. boron f. krypton

c. magnesium Mg g. fluorine

d. N h. oxygen

13. Distinguish between single bonds, double bonds and triple bonds. One pair of valence electrons is shared in a single bond. Two pairs of valence electrons are shared in a double bond. Three pairs of valence ctrons are shared in a triple bond.

14. Explain why the following Lewis structures for CHClO is incorrect.

H C O Cl

15. Draw Lewis structures (or structural formulas) for the following :

a. Cl2 e. hydrogen sulfide (H2S)

Cl Cl H S H

2 b. nitrogen trichloride (NCl3) f. silicon tetrahydride (SiH4)

H Cl N Cl H S H Cl H

c. carbon dioxide (CO2) g. methyl chloride (CH3Cl)

Cl O C O H H H

d. ethyne (C2H2) h. Phosphorus trihydride (PH3)

H C C H H N H H 16. Which (s) in question 15 include double bonds?

CO2, carbon dioxide 17. Which molecule(s) in question 15 have triple bonds?

C2H2, ethyne Part C 18. Write the correct formula for each of the following compounds. a. carbon monoxide CO b. sulfur dioxide SO2 c. diphosphorus pentoxide P2O5 d. nitrogen dioxide NO2 e. carbon dioxide CO2 f. phosphorus trichloride PCl3 g. dinitrogen pentoxide N2O5 h. phosphorus pentabromide PBr5 i. silicon dioxide SiO2 j. selenium tetrafluoride SeO4

3 19. Write the correct name for each of the following formulas.

a. N2O dinitrogen monoxide

b. P3N5 triphosphorus pentanitride

c. NI3 nitrogen triiodide

d. N2O4 dinitrogen tetroxide

e. P4O10 tetraphosphorus decoxide

f. SO3 sulfur trioxide

g. SiI4 silicon tetraiodide

h. N2O3 dinitrogen trioxide

i. CCl4 carbon trioxide

j. As2O5 diarsenic pentoxide

Part D

20. What is a ? A coordinate covalent bond occurs when one atom contributes both nding electrons in a covalent bond.

21. Draw Lewis structures (or structural diagrams) for the following polyatomic ions:

- - a. OH b. ClO3

22. State the Octet Rule. Name a compound in which the central atom does not follow this rule. The octet rule is the tendency of atoms to gain or lose electrons so that they acquire eight electrons in their outer level. BeH2 is an example of a compound with a central atom that does not following the octet rule.

23. Draw Lewis structures (or structural diagrams) for the following molecules.

a. BeH2 c. PCl5

b. SF6 d. BH3

4 - 23. What are resonance structures? Write the possible resonance structures for NO3

Part E 24. What do the letters VSEPR stand for? What is the basic assumption of this theory? VSEPR stands for the valence shell electron pair repulsion theory. This theory assumes that the atoms in a molecule will orient their positions so that the repulsive between the electrons are at a inimum. 25. How can you distinguish between a 3-atom linear molecule and a bent molecule? Give an example of each. A bent molecule has nonbonding electrons on the central atom. A linear molecule does not have nonbonding electrons on the central atom. An example of a linear molecule is BeH2. An example of a ent molecule is . 26. How can you distinguish between a trigonal pyramidal molecule and a trigonal planar molecule? Give an example of each. A trigonal pyramidal molecule has a pair of nonbonding electrons on the central atom. A trigonal planar molecule does not. An example of a trigonal pyramidal molecule is NH3. An example of a trigonal anar molecule is BH3. 27. Why is the bond angle in a trigonal pyramidal molecule different from that in a tetrahedral molecule? The nonbonding electron pair on the central atom of a trigonal pyramidal molecule exerts a greater repulsive force on the bonded atoms than an atom would. Therefore, the bonded atoms are pushed closer together in a trigonal pyramidal molecule and the bond angle is less. 28. What is the difference between a polar molecule and a nonpolar molecule? The charge distribution in a polar molecule is not uniform over the ends or outside of the molecule. One part of the molecule is more positive, and another part is more negative. This is known as a dipole. Nonpolar molecules do not have dipoles. 29. What makes a molecule polar? If a molecule has an uneven distribution of charge, that is, if one end is more negative or more positive than the other end, the molecule is polar. Polar molecules possess a molecular dipole. 30. Give two examples of polar molecules that contain polar bonds. Give two examples of nonpolar molecules that contain polar bonds.

5 31. Complete the following table. Lewis Structure (or Molecular Formula Name of Shape Structural Formula) Polarity

SbH3 Trigonal Pyramidal Polar

Cl2O Bent Polar

BeH2 Linear Polar

SiF4 Tetrahedral Nonpolar

Trigonal PI5 Bypyramidal Nonpolar

SCl6 Octahedral Nonpolar

CO2 Linear nonpolar

HCN Linear Polar

AsCl3 Trigonal Pyramidal Polar

BH3 Trigonal Planar Nonpolar

6 Part F 32. What is a van der Waals force? Is it an example of a chemical bond? Why or why not? A van der Waals force is a weak of attraction caused by electrostatic forces (attraction between opposite charges). It is not a chemical bond because electrons are not shared or exchanged.

33. What is hydrogen bonding? Is it an example of a chemical bond? Give an example of a substance that would exhibit hydrogen bonding. Hydrogen bonding is not chemical bonding. It is an intermolecular dipole-dipole attraction between molecules composed of hydrogen with fluorine, oxygen or nitrogen. Some substances that exhibit hydrogen bonding are water (H2O), ammonia (NH3), and hydrogen fluoride (HF).

34. Arrange the following intermolecular attractions in order of increasing strength: dipole-dipole , London dispersion forces, hydrogen bonds. London dispersion forces, dipole-dipole interactions, hydrogen bonds.

35. What is a temporary dipole? What types of molecules are capable of having temporary dipoles? What is the name of the van der Waals force that involves temporary dipoles? A temporary dipole is an uneven charge distribution that exists in an atom or molecule for a brief period of time. All atoms and molecules are capable of having temporary dipoles as their electrons move out to different locations. London forces are van der Waals forces th ar 36. For different substances of similar molar mass, which type of intermolecular force is the weakest? Give an example of a molecule that would exhibit this force. London forces are the weakest of the intermolecular forces for substances of a given mass. CO2, H2, Cl2, He, Ne, and Ar all exhibit London forces. 37. What type of intermolecular forces of attraction would be exhibited by each of the following substances? a. PF 3 dipole-dipole and London forces b. HF

c. N2 London forces

d. BeH2 London forces 38. The following substances have roughly the same molar mass. Which one is most likely to have the highest

boiling point: H2S, F2, or CO2? Explain your choice.

H2S will have the highest boiling point because it is a polar substance, whereas F2 and CO2 are nonpolar. The dipole-dipole interactions hold the H2S molecules together more tightly, requiring more energy for the molecules to separate in the boiling process. Content Review 39. A chemist wants to confirm whether a piece of metal is pure or an alloy of gold and less dense metal. She determines the volume by water displacement to be 6.35 mL and the mass of the object to be 101.6 g. Is the object pure gold? (The density of gold is 19.3 g/cm3.) You must show work to support your answer.

7 40. What tests would you perform on an unknown substance to decide whether it is an element or compound?

Compounds can be decomposed by chemical means, elements cannot. You could heat it or use electricity to try to decompose it into elements. 41. Complete the following table.

Nuclea r Number of Number of Number of Isotope Mass Number Symbo l Protons Electrons Neutrons titanium-47 Ti 22 22 25 47

tin-120 Sn 50 50 70 120

42. Write a balanced n u cle a r eq uati on f or e ach of th e following.

a. The alpha decay of Protactinium-231 Pa He Ac

b. The beta decay of Magnesium-28 Mg e Al

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