Honors Chemistry - Unit 4 Bonding Part I

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1 Honors Chemistry - Unit 4 Bonding Part I Unit 4 Packet - Page 1 of 8 Vocab Due: Quiz Date(s): Test Date: UT Quest Due: Bonding Vocabulary: see separate handout assignment OBJECTIVES: Chapters 4-8 Be able to identify the families on the periodic table. Be able to describe and identify the three types of bonds: ionic, molecular, and metallic. Be able to describe characteristics of ionic, molecular and metallic compounds. Be able to describe the difference between polar and nonpolar molecular bonds. Bond Type Type(s) of Atoms involved Force Properties Examples Relative Strength IONIC transfer of ( EN) is >1.7 Metal & Nonmetal or Metal and Polyatomic Ion Attraction between ions, opposite charges attract; transfer of High melting point High boiling point Water soluble Crystalline Aqueous solutions conduct a current NaCl MgO CaS K2SO4 (also includes covalent bonds) Generally the strongest bond type = the larger the ion charges the stronger the ionic bond. COVALENT Sharing of ( EN) is <1.7 METALLIC Free flow of Electrons Two Nonmetals Polar = unequal sharing = partial charge Nonpolar = equal sharing = no charge Two Metals Sharing of Sharing of between all atoms Low melting point Low boiling point Brittle Nonconductors Good conductors Malleable = shapeable Ductile = able to be drawn into a wire Water CO2 NH3 Copper wire Iron bar Weakest bond type- (exception network solids like diamonds)

2 BELLWORK REVIEW: 1. Write the noble gas configurations and dot diagram for Se. Unit 4 Packet - Page 2 of 8 2. ID the following as a metal or nonmetal: Ca, O, Sn, H, K, Cl and Li 3. Given: O, F and Cl put them in order of A. Decreasing atomic radius B. increasing electronegativity 4. If Candy cost 3.99 per pound - how many kilograms of candy can you buy with $10.00? New Material: 5. What is the octet rule? 6. A Use dot diagrams to show the transfer of for the following bonding: Ba and Cl. What type of bond is formed? 7. Use dot diagrams to show the sharing of for the following bonds: A. I and I B. H and O C. what type of bond is formed D. are they polar or nonpolar? 8. What type of bonds are found in the following: A. CH4 B. KCl C. Na3PO4 D. gold bar B. list the above in order of strongest bond to weakest bond.

3 Bonding Notes! Unit 4 Packet - Page 3 of 8 When bonds are formed atoms are following the octet rule trying to get 8 in its outer level. This is achieved by losing, gaining or sharing. Ionic Bonds: bond between a metal and a nonmetal or a polyatomic ion We can also classify bond type based on electronegativity; if the electronegativity difference ( EN) is >1.7 = ionic bond example using the electronegativity table in this packet, find the EN for the bond formed between Ca and N you try: find the EN for the bond formed between Li and F An ionic bond involves a transfer of : the metal loses e-s to get a (+) charge and the nonmetal gains e-s to get a (-) charge Ionic bonds are held together by electrostatic force (opposites attract!) When bonds are formed atoms are following the octet rule trying to get 8 in its outer level. (exception: H stable with just 2 valence ) Example 1: Copy off board: Mg and S Example 2: Ca and I You try: Al and F Together: we will label a shortcut for finding ionic charges on the PT (based on # of val e-s) Covalent Bonds: between two (or more) nonmetals Involves sharing (to get an octet = 8 valence e-s) Can also classify based on electronegativity if the electronegativity difference ( EN) is <1.7 = covalent bond Example: using the electronegativity table in this packet,find the EN for the bond formed between O and N Example 1: Copy off board: Show the bonding that occurs between Cl and F. Example 2: H and F hydrogen is an exception to the octet rule! You try: using Lewis dot diagrams illustrate the bonding that occurs between Br and I.

4 Covalent Bonds Involve sharing (to get an octet = 8 valence e-s) Unit 4 Packet - Page 4 of 8 equal sharing = nonpolar - no charge; this occurs when both elements have the same electronegativity (the attraction to an electron) o this occurs when there is a bond between 2 of the same nonmetal for example N2 both N have an equal pull on the shared electron pair so there is no partial charge. unequal sharing = polar slight charges; this occurs when the two elements have different electronegativities ie you have two different nonmetals in a covalent bond; the more electronegative element (the one further to the right and up on the PT) pulls more on the shared and has a slightly negative charge the other element will be slightly positive. Example: Classify the following as polar or nonpolar bonds: HCl, I2 You try: classify as polar or nonpolar: F2, NO ** There are some special molecular compounds called network solids (or network crystals) that contain extensive covalent bonding throughout a network of atoms. These compounds are very hard and brittle and have very high melting points examples: graphite and diamonds These are the strongest bonds! Metallic bonds: involves two metals the are delocalized metal ions plus a sea of mobile Polarity and Electronegativity When atoms share valence they do not always share them equally. Frequently one atom has a stronger attraction for the than the other atom does. This uneven attraction causes the to be held closer to one end of the bond than the other; we say this makes one end of the bond slightly positive and the other end of the bond slightly negative. A covalent bond with uneven sharing of the is called a polar covalent bond. A bond in which the are shared equally is called a nonpolar covalent bond. 1. Define the following terms: a. polar covalent b. nonpolar covalent Electronegativity is a measure of the ability of an atom of an element to attract to itself. Put another way, electronegativity is a measure of the force of attraction that exists between an atom and a shared pair of in a covalent bond. Linus Pauling developed a scale of electronegativities that run from a low of 0.7 for several metals in Group I to a high of 4.0 for fluorine.

5 Unit 4 Packet - Page 5 of 8 The table below gives Pauling Values for Electronegativity: H 2.1 He Li 1.0 Be B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Ne Na 0.9 Mg 1.2 Al Si P 2.1 S 2.5 Cl 3.0 Ar K 0.8 Ca 1.0 Sc 1.3 Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As 2.0 Se 2.4 Br 2.8 Kr Rb 0.8 Sr 1.0 Y 1.2 Zr 1.4 Nb Mo Tc Ru Rh Pd Ag Cd 1.7 In 1.7 Sn Sb Te 2.1 I 2.5 Xe Cs 0.7 Ba 0.9 La-Lu Hf 1.3 Ta W 1.7 Re Os Ir Pt Au 2.4 Hg Tl Pb Bi Po 2.0 At Rn Fr 0.7 Ra 0.9 Ac-Lr 1.1- We use electronegativity values when we discuss bond polarity. If two atoms sharing a pair of have equal values for electronegativity the bond is clearly nonpolar. As the difference in electronegativity increases the polarity of the bond increases, and if the difference in electronegativity is very large the bond is ionic. 1. What is electronegativity? 2. Sodium chloride (NaCl) is an example of an ionic bond. What is the difference in electronegativity between sodium and chlorine? 3. Nitrogen dioxide (NO2) is an example of a covalent bond. What is the difference in electronegativity between nitrogen and oxygen? It is difficult to decide exactly what we consider nonpolar, polar or ionic since bonds may have some covalent character and some ionic character. For convenience for beginning students we have established some arbitrary guidelines: Electronegativity Values Of The Elements, According To The Periodic Table Difference in electronegativity Intramolecular Bond Type nonpolar covalent polar covalent 1.7 or greater ionic

6 Unit 4 Packet - Page 6 of 8 Use the table and chart from this worksheet to label the following compounds as nonpolar, polar or ionic: a. NH3 b. MgO c. Cl2 d. HCl e.h2o f. NaCl g. CH4 h. NO2 Bond Strengths: Ionic: Generally the strongest bond type = the larger the ion charges the stronger the ionic bond ie Calcium Chloride, CaCl2 is stronger than potassium chloride KCl because Ca has 2+ charge involves 2 e- transferring and K has a 1+; only 1 e- transferring Metallic: medium strength between ionic and covalent Covalent: Weakest bond type- (exception network solids like diamonds- strongest bond type) Example problem: Classify the following from strongest to weakest bond: Copper wire, carbon dioxide, lithium chloride (LiCl) and aluminum oxide (Al2O3). You try: Rank the following from strongest to weakest bond: Water, potassium iodide (KI), pure gold necklace, and calcium fluoride (CaF2)

7 Bonding Basics Review Unit 4 Packet - Page 7 of 8 Element Bromine Atomic symbol Total # of Electrons # of Valence Electrons # of Electrons Gained or Lost Oxidation Number (charge) Lithium Calcium Sulfur Boron Silicon Phosphorus 2. Ionic Bonds - Draw the Lewis dot diagrams for each atom, draw arrows to show the transfer of, write the charge for each ion, and then write the chemical formula. (A) Potassium + sulfur (B) Magnesium + Oxygen (C) Lithium + Nitrogen 3. Covalent Bonds Draw the Lewis structures for each atom, draw lines to show the that are shared, and then write the chemical formula. (A) Fluorine + Fluorine (B) 3 Hydrogen + 1 Phosphorus (C) 2 Hydrogen + 1 Sulfur

8 Properties of ionic, covalent and metallic bonds: Unit 4 Packet - Page 8 of 8 Strongest bond type: remember this involves a transfer of. Because this is the strongest bond type: ionic compounds tend to have: melting points and boiling points (it takes more energy for these compounds to change states of matter). Are - they will break down into ions in water and will conduct an electric current. Ionic compounds tend to be brittle. Weakest bond type: remember this involves sharing. Because this is the weakest bond type: covalent bonds tend to have: melting points and boiling points (it requires less energy for these compounds to change states of matter). Are - they will not conduct an electric current in water. Covalent bonds may be polar (unequal sharing partial charges) or nonpolar (equal sharing no charges). Metallic bonds involve delocalized or a metal ion plus a sea of mobile. Metallic bonds have high melting points and high boiling points, the solid compound is highly conductive (metal compounds are not water soluble so they do not make electrolytic solutions with water but they are the only compounds that conduct a current (and heat) as a solid. They are malleable: and Ductile :