Presentation on theme: "#13 p. 229 in the book: What electron configurations"— Presentation transcript:
1 #13 p. 229 in the book: What electron configurations do atoms usually achieve by sharing electrons to formcovalent bonds?In forming covalent bonds, electron sharing usually occurs so thatatoms attain the electron configurations of noble gases.symbolelectron configurationheliumHe1s2neonNe[He]2s22p6argonAr[Ne]3s23p6kryptonKr[Ar]3d104s24p6xenonXe[Kr]4d105s25p6radonRn[Xe]4f145d106s26p6The s and p orbitalsare full (8 electrons)
2 #14 How is an electron dot structure used to represent a covalent bond?An electron dot structure such as H:H (seen below)represents the shared pair of electronsof the covalent bond by two dotsPlease see the on-line textbook Chapter 8 section 2simulation 6 CHEM ASAP! “simulate the covalent bonding between molecules”
4 #15 When are two atoms likely to form a double bond between them? A triple bond?Atoms form double or triple covalent bonds ifthey can attain a noble gas structure by sharingtwo pairs or three pairs of electrons.Oxygen isan exampleof two atomsjoining andsharing twopairs of elect-rons to forma double bond.
5 Nitrogen is an exampleof two atoms joining andsharing three pairs of elect-rons to form a triple bond.
6 #16 How is a coordinate covalent bond different from other covalent bonds?In most cova-lent bonds eachatom contributesone electron tothe bond. In acoordinate coval-ent bond bothelectrons arecontributed bythe same atomOxygen has to “kick in” two additional electrons toallow both to have a full octet (eight total) valenceelectrons
7 #17 How is the strength of a covalent bond related to its bond dissociation energy?A large bond dissociation energycorresponds to a strong covalent bond.As you can see in thetable on the right dif-ferent covalent bondshave different amountsof energy needed tobreak apart. A largedissociation energy(see N triple N) is astrong bond. A low(see N-O) is a weakbond.
8 #18 Draw the electron dot resonance structures for ozone and explain how they describe itsbonding.When you have two equally valid options for dot structureas seen above you have RESONANCE.Click here to see a movie about how ozone is formed in the upper atmosphereand its importance in shielding the earth from Ultraviolet radiationClick here to see a movie about how ozone is destroyed by CFC’s
9 O N O #19 List three ways in which the octet rule can sometimes fail to be obeyed.The octet rule cannot be satisfied in molecules:1. whose total number of valence electrons is an odd number.2. There are also molecules in which an atom has FEWER THAN 8 valenceelectrons,3. Molecules with MORE than a complete octet of valence electrons.●●●●●●Nitrogen hasonly 7 valenceelectrons●O N O●●●●●●1. Nitrogenas an ODDnumber (5)of valenceelectronsand thussometimesdoes notobey the octetrule●●●●
10 #19 continued2. The boron in BF3 has a deficiency of valence electrons (only 6 total) so it doesn’t obey the octet ruleFFB3. In the case of PCl5 and SF6 the P and the S have MORE THAN the octet (Phas 10 and S has 12)F
11 #20 What kinds of information does a structural formula reveal about the compound it represents?It reveals the way the atoms are bonded together:ie; single bonds, double bonds, triple bonds, and bond angles, unshared pairs, etc.
12 H2S S H H #21 Draw electron dot structures for the following molecules which have onlysingle covalent bonds.H2SSHH
15 The hydrogen bond is stronger due to its greater bond dissociation # 22. Use the bond dissociation energies ofH2 (435 kJ/mole) and of a typical carbon-carbon bond (347kJ/mole) to decide whichbond is stronger. Explain your reasoning.The hydrogenbond is strongerdue to its greaterbond dissociationenergy (theamount of energyneeded to breakit.)