Quiz today over Covalent bonding Need to turn in all missing work today! • Take out your lab. Staple it together but don’t turn it in the basket. I am going to collect them from you when the bell rings. • Take out your Molecular Shape Lab. We are going to finish it. • DCA next class! Which bond is more polar: (find the electronegativity difference) A) H-S B) H-O C) H-Si Name that bond! 1. What type of bond(s) does KCl have? 2. What type of bond(s) does KOH have? 3. What type of bond(s) does K have? • http://phet.colorado.edu/en/simulation/mol ecule-shapes VSEPR THEORY: •How do we determine the shapes of molecules and ions? VSEPR THEORY • What does VSEPR stand for? • Valence Shell Electron Pair Repulsion • Electrons repel each other just like magnets! Molecular geometries • Lewis structures help us understand the type of bonds between atoms in a molecule • But, they do NOT indicate the geometry in 3-D space. • VSEPR theory helps describe the actual geometry of molecules based on their covalent bonding. VSEPR Theory • Valence Shell Electron Pair Repulsion Theory • Electrons repel one another so they try to be as FAR AWAY from each other as possible • This determines the shape (think 3D) C. Johannesson VSEPR Theory • Lone pairs reduce the bond angle between atoms. Bond Angle C. Johannesson VSEPR THEORY (VALENCE SHELL ELECTRON REPULSION) NO CENTRAL ATOM LINEAR SHAPE (ALL DIATOMICS ARE LINEAR :H2 N2 O2 and ALL OF GROUP 7A) 2 ATOMS AROUND A CENTRAL ATOM LINEAR SHAPE ( BF2 HCN ) UNBONDED OF ELECTRONS ON CENTRAL ATOM BENT SHAPE ( H2O H2PAIR S NO 2) ) TRIGONAL PLANAR SHAPE ( BF3 3 ATOMS AROUND A CENTRAL ATOM UNBONDED ELECTRONS ON CENTRAL ATOM TRIGONAL PYRAMIDAL ( NH3 H3As ) 4 ATOMS AROUND A CENTRAL ATOM TETRAHEDRAL SHAPE ( CCl4 CF4 CH4 ) 25 min review 15 min finish quiz 20 min metallic bonding 30 min quiz • Allow 15 minutes to finish up the “lab” • Talk about bond strength- triple is the strongest • Give example of KNO3 has both an ionic bond and a covalent bond while KCl is ionic and K is just metallic • Look for the Jump Street 21 clip… • http://www.bsc2.ehbschweiz2.ch/Chemie/Simulationen%20Ch emie/Bindung/Bindung%20Hundeanalogie .htm Polar Covalent bonds • Polar = unequal sharing of electrons due to electronegative difference • This creates a “partial positive charge” and “partial negative charge” • Separation of charge creates a dipole. • https://www.youtube.com/watch?v=PVL24 HAesnc&index=23&list=PL8dPuuaLjXtPH zzYuWy6fYEaX9mQQ8oGr • Polar bond acts as a dipole. • Dipole = electronic vector with a magnitude and a direction. • • Equal in magnitude and opposite direction cancel to give nonpolar molecule. For a molecule to be polar, 2 conditions must both be met 1. There must be at least one polar bond or one lone (unshared) pair on the central atom. And 2. A. The polar bonds, if there are more than one, must not be arranged so that their polarities (bond dipoles) cancel. Or B. If there are two or more lone (unshared) pairs on the central atom, they must not be arranged so that their polarities cancel. • Which bond is more polar, HCl or HBr? Hybridization • A new set of orbitals (hybrid orbitals) are created by mixing s, p, and d (if needed). Hybridization • http://www.youtube.com/watch?v=g1fGXD RxS6k To understand how molecules really are: • https://www.youtube.com/watch?v=cPDptc 0wUYI&list=PL8dPuuaLjXtPHzzYuWy6fY EaX9mQQ8oGr&index=25 You now have 15 minutes to finish your VSEPR “Quiz” with your group Quiz Time!