Chem 1070 1st Edition Lecture 21 Outline of Last Lecture I. Valence ElectronsOutline of Current Lecture II. Covalent and Ionic BondsCurrent LectureLewis Theory and Bond Formation • Bonds form when valence electrons on adjacent atoms interact. • Ionic bonds involve transfer of electrons between atoms to form ions and ionic bonds. • Covalent bonds involve sharing of electrons between atoms to form covalent bonds. • Usually, stable bonds form when each atom has a noble gas configuration (8 electrons), consistent with a filled shell (octet). – Exceptions around the duet of He: filled shell He, H, Li, Be 2 electrons for stable bond Lewis dots for Covalent Compounds • Covalent Bonds– Usually two nonmetals– Typical of molecular species– Strong attraction between atoms of molecule • Atoms share pairs of electrons to form bonds and attain octets. • To form octets, multiple bonds (double, triple) may be needed. • Covalent compounds have weak intermolecular attractions. – Attractions set physical properties. • Ionic compounds • Strong bonds: smaller ions higher charge • – usually one metal and one nonmetal These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• – formed of ions (metal→cation nonmetal→anion) • – elements in ionic compounds transfer electrons to form bonds and make ions EXCEPTIONS TO OCTET RULEExpanded “octets” (into d orbitals)>8electrons SF6 and PCl5 2. Boron6electrons 3. Odd number of valence electrons a. not all atoms achieve octet b. do the best you can; try for octet on central
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