Chapter 8 Flashcards
what are the 3 major types of bonding?
ionic
metallic
covalent
what is ionic bonding?
electrostatic attraction (K2ClO4, MgO, NiO)(metal + nonmetal)
what is covalent bonding?
electrons are shared (Br2, S8, C6H12O6)(nonmetals)
- for covalent bonding to occur, ionic bonding must be energetically unfavorable
what is metallic bonding?
electrons are delocalized (Au, Mg, Cu)
what is the octet rule?
atoms gain, lose, or share electrons to achieve a nobel gas configuration
what is an ionic bond?
an ionic bond is the electrostatic attraction between positive and negative ions resulting from electron transfer
Na + Cl —> Na+ + Cl-
why are noble gas configurations very stable?
attractive forces between ions of opposite charge are maximized
repulsive forces between ions of the same charge are minimized
what is lattice energy?
the energy required to separate 1 mole of solid ionics into gas ions
NaCl(s) —> Na+(g) + Cl-(g)
LE parallels melting point/boiling point
what is the formula for lattice energy?
LE = Q1Q2/d
charge is more important than distance: +3 > +2 > +1
KCl vs. CaO: CaO has higher LE because CaO has +2,-2 charges while KCl has +1, -1 charges
LiF vs. LiI: same charges….so now you go for the distance: iodine is larger than fluorine so LiF will have higher LE
born haber cycle
Hrxn = Hf(metal) + Hf(nonmetal) + IE(metal) - EA(nonmetal) - LE
must be in gas phase*
what is a double bond?
pi bond
what happens to distance and strength as bond numbers increase?
when there is more than one electron pair between two atoms, the atoms are pulled closer together and the bond length is shorter - bond energy increases
EN trend?
electronegativity increases from left to right and from bottom to top
ionic or covalent based on EN?
ΔEN < .5 nonpolar covalent
ΔEN > 1.9 - 2.1 ionic
state and electronegativity?
if gas or liquid, it tends to be more covalent
if something is a solid it tends to be more ionic
dipole moment formula?
Q= μ/r
formal charge
valence electrons - #electrons assigned to atom
the most stable structure has the smallest formal charge on each atom - and the most negative charge on the most electronegative atom
what are the 3 exceptions to the octet rule?
- odd number of valence electrons (NO, NO2, ClO2)
- central atom has less than an octet (Be or B: BeCl2, BF3)
- central atom has more than an octet below 2nd period, atoms are large, have d orbitals (SF6, PCl5, AsF6-, ClF4+
why do we not see compounds of helium or neon but we do see compounds of krypton or xenon?
He and Ne are smaller and have higher IE than Kr or Ze so they are less reactive. Also, Kr and Ze have d orbitals while He and Ne only have s and p
the valence electrons have the greatest freedom to move in compounds where atoms are held together by….
covalent bonding
