CHAPTER 7 CHEMICAL FORMULAS AND BONDING Date _____________ covalent bonding / Lewis diagrams ionic _________________________________ the metal atom(s) _______________ enough ______________ to the nonmetal atom(s) so that each resulting __________ has a _______________ the resulting ____________ and _____________ attract covalent ______________________________ enough atoms _____________ enough __________________ so that each atom ends up with ___________________________ somehow ___________________________ holds atoms together….. but electrons are all __________________ they __________________ how can they “glue” atoms together …!!! ??? metal plus nonmetal transfer electrons e- ion FOS cation anion - + nonmetal plus nonmetal share electrons the equivalent of a FOS sharing electrons e- negative REPEL e-

BUT 1s 1 p+ p+ e- e- p+ p+ e- e- covalent bonding ___________________________ use H2 as an example… 1H _____ electrons shared oo ooo oooo look at that dudette over there… 1s 1 a hydrogen atom alone in the cosmos… another hydrogen atom alone in the cosmos… attract p+ p+ e- e- attract attract attractions pull the atoms closer… BUT repulsions push the atoms apart… attract p+ p+ e- e- repel attract attract repel

p+ p+ e- e- covalent bonding ___________________________ electrons shared attractions pull the atoms closer… BUT repulsions push the atoms apart… attract p+ p+ e- e- repel attract attract repel there will be a position (distance) where ______________________________________ the orbitals _______________________ attractions and repulsions balance overlap

nuclei preferentially attracted to the “overlap” covalent bonding ___________________________ electrons shared attractions pull the atoms closer… BUT repulsions push the atoms apart… p+ p+ e- e- nuclei preferentially attracted to the “overlap” there will be a position (distance) where ______________________________________ the orbitals _______________________ orbital represents ___________________________ overlap = ___________________________________ ___________________________________________ (that’s the bond) attractions and repulsions balance overlap probability of where electrons can be increased probability electrons more likely to be BETWEEN the nuclei

nuclei preferentially attracted to the “overlap” covalent bonding ___________________________ electrons shared attractions pull the atoms closer… BUT repulsions push the atoms apart… p+ p+ e- e- nuclei preferentially attracted to the “overlap” the electrons are now shared in a new space…. a new _________________ that belongs to both atoms how many electrons per orbital ? _______________ so each covalent bond is made up of _______ shared electrons (that’s the glue) orbital TWO TWO

Lewis structures (electron dot diagrams of formula units, molecules, and polyatomic ions) saw examples for ionic…. for covalent… shows distribution of _________ electrons and how they are _________ so that each atom achieves the equivalent of a _________ electrons are shared in ______ 1 shared pair = _________ does NOT deal with how bonds are formed does allow one to deduce the _______________________________ equivalent of a FOS ______________________________ (something about ______________) comes from… if outer shell of a single atom is full, the outer s- and p- sublevels are ___________ holding a total of _________________ this leads to a strong driving force for an atom to “have” an octet of electrons in a molecule by achieved by sharing valence shared FOS pairs one covalent bond two atoms can share ___________________________ ______________________________ 1 pair = single bond 2 pairs = double bond 3 pairs = triple bond 3D structure (structure  properties)  “octet” rule eight full eight electrons

Rules for Lewis Structures (for covalent structures… molecules and polyatomic ions) Draw a skeleton (a frame) Count valence electrons – total for all atoms place the least electronegative atom in the middle (central atom) EXCEPT for Hydrogen (of course!)… only has 1e to share… so can only make one bond…. so can’t go in the middle place the remaining atoms in some symmetrical pattern around the central atom

Place the valence electrons into the structure… b. c. 2 electrons between each bonding pair of atoms place valence electrons in pairs around the outside atoms to achieve an octet EXCEPT for Hydrogen… only wants a “duet” place any remaining valence electrons (in pairs) on the central atom as nonbonding pairs (not shared) ** at this point, the central atom may have more than an octet

At this point, if the central atom has LESS than an octet… use nonbonding pairs of electrons from the outside atoms to make double / triple bonds with the central atom (the non-bonding electrons now become shared) A few points…. central atom ___________________________________ outside atom ___________________________________ for diatomics ___________________________________ _______________________________________ an atom bonded to more than one other atom an atom bonded to one other atom arbitrarily choose one of the atoms as the central atom and then follow the rules (but remember… there is no central atom)