CHEM 150 1nd Edition Chapter 8: Chemical Bonding and Climate Change Lecture 25Outline of Last Lecture • Periodic trends:• Atomic radii: atoms tend to be larger as you move left and down on the periodic table.• Moving down a group, the valence shell gets farther from the nucleus• Moving right across the period: the effective nuclear charge is growing (shielding is constant but Z increases) so the valence shell is pulled closer to the nucleus.Outline of Current Lecture • Chemical Bonds (section 8.1)• Understand the definitions of and differences between ionic bonds, covalent bonds, and metallic bonds.• Understand how figure 8.1 (p 369) relates bond energy and bond length to the attractive and repulsive forces present in the atom.Current Lecture-Know the terms bond length, bond energy (bond strength), and bond order. Know how these bond properties are related (Section 8.8).Q: Rank these bonds in order of increasing bond length: P-O, P-Cl, S-OA: -Rank them in order of increasing bond strengthA:Q:Rank the following bonds in order of increasing bond length: N-N, N=N, N/NA: Q: Which has the higher bond energy:N-O or N=O?• Polar covalent bonds: bonds in which the electrons are shared unequally between two atoms.• Electronegativity is a measure of an atoms ability to attract electrons in a covalentbond.• The electrons will spend more time near the atom with the highest electronegativity.• Indicate the direction of polarity in the following bonds: S-O C-F H-N H-Si P-Br O-Cl• Rank the bonds above in order of increasing polarity-Lewis dot symbols: The atomic symbol surrounded by a dot for each valence electron present in the atom.Q: Draw Lewis dot symbols for the following:O Ca Ge ArA: -Octet Rule: Main group elements gain, lose or share electrons to achieve a set of eight valence electrons.-Lewis Structures for covalently bonded (molecular) compounds:-Bonds are shown as lines. Lone pairs of electrons (non-bonding) are shown as pairs of dots.-General Rules:All atoms must have a set of eight valence e in the final molecule. [Except: H, Be, B]An atom will usually form one bond for each electron it requires. [One bond per unpairede- in the Lewis dot symbol.]Q: Draw the Lewis struchtures of F2O, NH3, CCl4, and
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