Chem C103 Bonding and Grouping of Elements
Chem C103 Bonding and Grouping of Elements CHEM-C 103
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This 13 page Class Notes was uploaded by Meegan Voss on Sunday January 24, 2016. The Class Notes belongs to CHEM-C 103 at Indiana University taught by Arnold K / Snaddon D in Fall 2015. Since its upload, it has received 32 views. For similar materials see INTRO TO CHEMICAL PRINCIPLES in Chemistry at Indiana University.
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Date Created: 01/24/16
9/22/2015 Types of Bonds Lewis Bonding Theory •Atoms bond because it results in a ___________ electron configuration. •More stable = lower potential energy •Atoms bond together by either transferring or sharing electrons. •Usually this results in all atoms obtaining an outer shell with eight electrons. •Octet rule •There are some exceptions to this rule—the key to remember is to try to get an electron configuration like a noble gas. 1 9/22/2015 Octet Rule • When atoms bond, they tend to gain, lose, or share electrons to result in _________valence electrons. • ________________ • Noble gas configuration • Many exceptions • H, Li, Be, B attain an electron configuration like He. • He = two valence electrons, a duet. • Li loses its one valence electron. • H shares or gains one electron. + o Though it commonly loses its one electron to become H • Be loses two electrons to become Be .2+ o Though it commonly shares its two electrons in covalent bonds, resulting in four valence electrons • B loses three electrons to become B .+ o Though it commonly shares its three electrons in covalent bonds, resulting in six valence electrons • Expanded octets for elements in period 3 or below • Using empty valence d orbitals Lewis Theory and Ionic Bonding Lewis symbols can be used to represent the transfer of electrons from metal atom to nonmetal atom, resulting in ions that are attracted to each other and therefore bond. 2 9/22/2015 Properties of Ionic Compounds • Hard and brittle crystalline ___________ •All are solids at room temperature • Melting points generally > 300 ▯C • The liquid state conducts electricity •The solid state does ____ conduct electricity • Many are ________ in water •The solution conducts electricity well Conductivity of NaCl In NaCl(s), the In NaCl(aq), ions are stuck in the ions are position and not separated and allowed to move to the charged allowed to rods. move to the charged rods. 3 9/22/2015 Lewis Theory of Covalent Bonding •Lewis theory implies that another way atoms can achieve an octet of valence electrons is to _______ their valence electrons with other atoms. •The shared electrons would then count toward _______ atom’s octet. •The sharing of valence electrons is called covalent bonding. Covalent Bonding: Bonding and Lone Pair Electrons • Electrons that are shared by atoms are called _________________ • Electrons that are not shared by atoms but belong to a particular atom are called ________________ – Also known as nonbonding pairs 4 9/22/2015 Single Covalent Bonds • When two atoms share one pair of electrons, it is called a ______________ bond. ▯Two electrons • One atom may use more than one single bond to fulfill its octet. ▯To different atoms ▯H only duet Double Covalent Bond •When two atoms share two pairs of electrons the result is called a double covalent bond. •Four electrons 5 9/22/2015 Triple Covalent Bond •When two atoms share three pairs of electrons the result is called a triple covalent bond. •Six electrons N 2 Polar Covalent Bonding • Covalent bonding between unlike atoms results in ________ _______________of the electrons. • One atom pulls the electrons in the bond closer to its side. • One end of the bond has larger electron density than the other. • The result is a polar covalent bond. • Bond polarity • The end with the larger electron density gets a partial negative charge. • The end that is electron deficient gets a partial positive charge. 6 9/22/2015 HF ▯▯ ▯ EN 2.1 H F EN 4.0 ▯ ▯▯ ▯▯ H • F ▯▯ • Electronegativity •The ability of an atom to attract bonding electrons to itself is called electronegativity. •Increases across period (__________________) and decreases down group (__________________) •_____________is the most electronegative element. •_____________is the least electronegative element. •Noble gas atoms are not assigned values. •The larger the difference in electronegativity, the more polar the bond. •Negative end toward more electronegative atom. 7 9/22/2015 Electronegativity Scale 8 9/22/2015 VSEPR Theory • Electron groups around the central atom will be most stable when they are as___________________________. We call thisvalence shell electron pair repulsion theory. • Because electrons are negatively charged, they should be most stable when they are separated as much as possible. • The resulting geometric arrangement will allow us to predict the shapes and bond angles in the molecule. Electron Groups •The Lewis structure predicts the number of valence electron pairs around the central atom(s). •Each lone pair of electrons constitutes one electron group on a central atom. •Each bond constitutes one electron group on a central atom, regardless of whether it is single, double, or triple. •• •• There are _____ electron groups on N: • •• •rpol_ • ON O • ••dbens_ nbed_ 9 9/22/2015 Two Electron Groups: Linear Electron Geometry •When there are ____________groups around the central atom, they will occupy positions on opposite sides of the central atom. •This results in the electron groups taking a linear geometry. •The bond angle is 180° Three Electron Groups: Trigonal Planar Electron Geometry •When there are ____________ groups around the central atom, they will occupy positions in the shape of a triangle around the central atom. •This results in the electron groups taking a trigonal planar geometry. •The bond angle is 120°. 10 9/22/2015 Four Electron Groups: Tetrahedral Electron Geometry •When there are four electron groups around the central atom, they will occupy positions in the shape of a tetrahedron around the central atom. •This results in the electron groups taking a tetrahedral geometry. •The bond angle is 109.5°. Bond Angle Distortion from Lone Pairs 11 9/22/2015 Molecule Polarity The H─Cl bond is________. The bonding electrons are pulled toward the ____ end of the molecule. The net result is a____________________. 12 9/22/2015 Molecule Polarity The O─C bond is__________. The bonding electrons are pulled __________toward both O ends of the molecule. The net result is a ______________molecule. Molecule Polarity The H─O bond is_________. Both sets of bonding electrons are pulled toward the O end of the molecule. The net result is a __________molecule. 13
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