Types of Bonding and Attractive Forces. Crystalline structures show regular 3-D repeating lattice of particles (ions or metal kernels).

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1 fc -e ia. Ohsmistry information Sheet Types of Bonding and Attractive Forces Bonding Unit Intramolecular Intermolecular Examples None None dispersion (London) He, Ne, Ar Molecule Nonpolar covalent dispersion h2, ci2i o2, ch4 Molecule Polar covalent Dipole or HBr, HCI, H2CO or hydrogen bonding NH3, H20, HF Ionic crystal Ionic NaCI, KBr, CaF2 Metal crystal Metallic Cu, W, Na or alloys Crystalline structures show regular 3-D repeating lattice of particles (ions or metal kernels). Intramolecular forces are the strong forces that hold atoms or ions together (BONDS) Intermolecular forces are the weaker forces that bind one molecule to an adjacent molecule. Also know as VanderWaals forces. a) Dispersion forces (London) are of the induced dipole type. They occur due to the movement of electrons in the cloud and are ery weak and temporary. Generally, the more electrons in a molecule, the stronger the London forces. b) Dipole-Dipole interactions occur due to the attractions caused by the weakly positive and negative ends of polar molecules. They cause the molecules to align and are stronger than London forces. c) Hydrogen bonds are a special type of polar bond that occurs only when a hydrogen atom is bonded to a N, O, or F atom. These very small and highly electronegative elements pull the shared electron pair very strongly away from the H nucleus and in doing this leave the proton(h nucleus) exposed. This gives a positive center that is able to attract the negative ends of nearby molecules. This additional attraction is stronger than ordinary dipole attractions and gives the compounds additional structure strength (as in DNA and the folding of proteins) or causes an increase in MR and BP (as is seen in HF and H20)

2 Tnnic Vs. Covalent When two atoms combine they form Ionic Compounds: Molecule (Covalent or Molecular Co pounds)

3 Chemistry Worksheet Name Period Date Bonding Concepts Practice Elements A EN Bond Type Electron dot diag. Na + Cl K + F Li + S C + H Be + S Mg + N Si + F Al + N C + Cl C + F S + 0 Ge + H C + Br Ca + F

4 Dot Diagrams for Practice: On your paper make an electron dot diagram for each formula given. Count electrons and octets to double check Hint: If there are three elements in the molecule. The element in the middle of the formula frequently (not always) is in the middle of the molecule. Symmetry is a way for minimizing repulsion. Charges reflect electrons that have been added in or lost. easy moderate hard 1. h2o HCI04 +1 NH 4 2. ch2ci2 H2S04 hpo; 3. Phl3 C2H6 no2"1 4. CBr HCN cio 1 5. h2s C2H h2co: 6. CH3Br co2 NC 1 5

5 Octet Rule Chemist: Date: For the following molecules 1. Draw out their Lewis do stiucture using the Octet rule provided below 2. If the molecule does not obey the octet rule, explain why../hour: Octet Rule I Count the valence electrons of the elements m the compound and add all of them together. 2. Divide the # of valence electrons by 2 to get the number of pairs. 3. Draw the simplest structure possible with 8 electrons round each atom an the toms lin ed by single bon s 4. Count all elect on pairs, both lone and bonded. I the number of electron pairs equals #2, then this is the form of the molecule If the numbers are not the s me, form double and triple bonds as needed. Rem mber keep either 8 electrons or 2 electrons a ound every atom a SO k AsBr5 b. CN i. Beh c S O m. CO d. NCI n SO3 " e. Cb 0. NH4+I

6 Name Date Cl ss Chemical Bonding SECTION 6-1 SHORT ANSWER Answer the following questions In the space pro ided. 1. A chemical bond between atoms results from the attraction bet een electrons and (a) protons (c) isotopes (b) neutrons (d) Lewis structures 2. _ A covalent bond consists of (a) a shared electron (c) two different ions (b) a shared electron a r (d) an octet of electrons If two covalently bonded atoms are identical, the bond is identified as (a) nonpolar covalent (c) nonionic (b) polar covalent (d) dipolai A covalent bond in which there is an unequ l attraction for the shared electrons is (a) nonpolar (c) ionic (b) polar (d) dipolar Atoms with a strong attraction for electrons they shaie with another atom exhibit (a) zero electionegativity (c) high electronegativity (b) low electronegati ity (d) Lewis electronegativity Bonds that possess between 5% and 50% ionic character are considered to be (a) ionic (c) polaf covalent ( ) pure covalent (d) nonpolar covalent The greater the electronegativity difference between two atoms bonded together, the greater the bond s peicentage of (a) ionic character (c) m tallic character (b) covalent character (d) electron sharing 8. The electrons involved in the formation of chemical bond are called 9. A chemical bond that results from the electrostatic attraction between positive and negative ions is c lled a(n) MODERN CHEMISTRY SECTION 6-1 REVIEW 41 HRW material cop righted un er notice appearing earlier in this work

7 Name Date Class CHAPTER 6 REVIEW Chemical Bonding SECTION 6-2 SHORT ANSWER Answer the following questions in the space provided. 1. Use the concept of potenti l energy to describe how a covalent bond for s between two atoms. 2. Name two elements that form compounds that are exceptions to the octet rule. 3. Explain hy resonance structures illustrate the limitations of Lewis structures in correctly modeling covalent bonds. 4. Bond energy is related to bond length Use the data in the tables below to arrange the bonds listed m order of increasing bond length, from shortest bond to longest. a. Bond Bond energy (ki/mol) H--F 569 H H--Cl 432 H--Br 366 MODERN CHEMISTRY S CTION 6-2 REVIEW 43 HRW materia! copyrighted un er notice appearing earlie In ihli work,

8 Name Date. Class Chemical Bonding SECTION 6-3 SHORT ANSWE Answer the following questions in the space provided. 1. The notation for sodium chloride, N Cl, stands for one (a) formula unit (c) crystal (b) molecule (d) atom 2. In a crystal of an ionic compound, e ch cation is surrounded by a nu ber of (a) molecules (c) dipole (b) positive ions (d) negative ions 3. Co ared with the neutral ato s involved in the for tion of an ionic compound, the crystal lattice that results is (a) higher in potential en rgy (c) equal in potenti l energy (b) lower in potential energy (d) unstable 4. The lattice energy of compound A is gre ter than that of compound B. What can be concluded from this fact1 (a) Compound A is not an ionic compound (b) It will be more difficult to bieak the bonds in compound A than in compound B. (c) Compound B is probably a gas. (d) Compound A has larger crystals than compound B. 5. The forces of attr ction between molecules in a molecular compound are (a) stronger th n the attractive forces in ionic bonding (b) weaker than the attractive forces m ionic bonding (c) approximately equal to the attractive forces in ionic bonding (d) equal to zero 6. Describe the force that holds two atoms together in an ionic bond. 7. What t pe of energy best repres nts the strength of n ionic bond? MODERN CHEMISTRY SECTION 6-3 EVIEW 45 HRW maten l cop righted under notice ap earing earlier in this work

9 Name Date Class SECTION 6-3 continued 8. What type of bonding holds a polyatomic ion together9. Arrange the ionic bonds in the table below in order of increasing strength from weakest bond to strongest. Ionic bond NaCl -787 CaO KCI -715 MgO LiCJ -861 Lattice energy (kl/mol) 10. Draw Lewis structures for the following polyatomic ionsa. NH4 b. SO " 11. Draw the two resonance structures for the nitrite anion, N SECTION 6-3 REVIEW MODERN CHEMISTRY HRW material copyrighted un er notice appearing earlier in this work.

10 // Name Date Class CHAPTER REVIEW Chemical Bonding SHORT ANSWER Answer the following questions in the space provided. 1. In metals, the valence electrons are considered to be (a) attached to particular positive ions (c) immobile (b) shared by all surrounding atoms (d) involved in covalent bonds 2. The fact that metals are malleable and ionic crystals are brittle is best explained m terms of their (a) chemical bonds (c) heats of vaporization (b) London forces (d) polarity 3. As light strikes the surface of a metal, the electrons in the electron sea (a) allow the light to pass through (b) become attached to particular positive ions (c) fall to lower energy levels (d) absorb and re-emit the light 4. Mobile electrons in the etallic bond are responsible for (a) luster (c) electrical conductivity (b) thermal conductivity (d) all of the above 5. In general, the strength of the metallic bond moving from left to right on any row of the periodic table (a) increases (b) decreases (c) remains the same 6. When a metal is drawn into a wire, the metallic bonds (a) break easil (c) do not break (b) break with difficulty (d) become ionic bon s 7. Use the concept of electron configurations o explain why the number of valence electrons in metals tends to be less than the number in most nonmetals. i MODERN CHEMISTRY SECTIO 6-4 REVIEW 47 HRW material copyrighted under notice appearing earlier in t is work

11 Name Date Class Chemical Bonding SHORT ANSWER Answer the following questions in the space provided. 1. Identify the major assumption of the VSEPR theory that is used to predict the shape of atoms. 2. In w ter, two hydrogen atoms are bonded to one oxygen atom. Why isn t water a linear molecule? 3. What orbitals combine together to form sp3 hybrid orbitals around a carbon ato 7 4. What t o factors determine whether or not a molecule is polar? 5. Arrange the following types of attractions in order of increasing strength, with 1 being the weakest and 4 the strongest. covalent ionic di ole-dipole London dispersion 6. How are dipole-dipole attractions, London dispersion forces, and hydrogen bondin similar? MODERN CHEMISTRY SECTION 6-5 REVIEW 49 HRW mnlcnnl copyrighted under notice appoering earlier In this work

12 Chemistry Laboratory Name Period Date IONIC or COVALENT What kind of bond is it? Purpose- Determine the type of bonding in a compound using characteristic properties. Ionic compounds are cr stalline substances composed of ions with strong attractions between them Because of this, they are solids at room temperature, have generally high MR and will only conduct electricity if dissolved in water Covalent compounds, are molecular substances with weaker attractions between molecules They vary in phase and generally have low MR Some are soluble but many are not Procedure: 1. For each sample, write down the name and/or formula of the compound being tested. Fill a well in the well plate approximately 1 full 2. Insert the electrodes of the conductivity tester into the solution and observe the LED Be sure the two wires are not touching each other. If it lights up the solution conducts current Mark your data table as either yes or no for conductivity 3. Also at each table is a pure sample of the compound. Observe the container and write the physical state (solid, liquid, gas) for each sample DO NOT OPEN ANY OF THE JARS OR BOTTLES Homework: Use the internet to search out and find the melting point of each substance Make sure to use a reputable source (not Patty s Pretty Periodic Table) for your information Data Table: Substance Conductivity State (20,C) Melting Point ( C) Predicted bond type

13 Chemistry Laboratory Name Period Date Substance Conductivity State (20 C) Melting Point ( C) Predicted bond type Questions: 1. Based on the state ata only, which of the substances do you predict will be ionic? 2. Based on the conductivity data only, which do you predict will be ionic? 3 Which substance(s) ha e discrepancies in the first two questions? 4. Explain the relationship you see in your data between the type of bonds, ion formation/presence in water, and conductivity 5. The pure compound hydrogen chloride (HCI) is covalently bonded and yet it conducts electricity when it is dissolved in water. The equation here shows what happens when HCI dissolves HCI(g) + H20 (1) -> H30+1(aq) + cr1(aq) Explain how it is possible for some covalent compounds(!ike this) to conduct current

14 Bonding Lab Form - Molecular Models Formula h2 Structural Drawing Electron Dot Diagram AEN Bond type Molecular Shape Polar or Nonpolar molecule h2o NaCI HCI nh3 aif3 ) ch4 CCI4 ch2o o f2 h2o2 1

15 c2h6 J c2h6o C2H4 cs2 c3h6 G2H20I2 ( c3h8o (