exam 3: chapters 8 & 9 Flashcards
Ionic bond
metal + nonmetal
(cation + anion)
- EN > 1.7
Covalent
nonmetal + nonmetal
- sharing of e- b/w 2 atoms
Nonpolar
covalent b/w same element
- equal pull
ionic bonding
metal loses e-, nonmetal gains e-
Born-Haber Cycle (energetics of ionic bonding):
- Break into separate elements
- Add energy (heat) to transform Na (s)(g)
- Add energy (heat) to transform ½Cl2 (g) (g)
- Electron is transfers/added to Cl (g)
- Opposites attract; Na and Cl attract
Lattice energy
energy to separate 1 mol of (s) –> 2 ions (g)
- ↑ w/ ↑ charge of ions
- ↑ w/ ↓ size of ions
charge > energy
- consumes energy
Lewis’ Rule
Column/group # = # of valence e-
- ex: group 3A = 3 v. e-
Octet rule
atoms tend to gain, lose, or share electrons until they’re surrounded by 8 valence e-
- (full s and p subshells)
↑ # bonds = __ distance
= ↓ distance
- additional bonding e- attract nuclei more
Bond polarity
measures how equal/unequal e- shared in covalent bond
nonpolar covalent bond
e- shared equally
- EN < 0.4
polar covalent bond
1 atom exerts greater attraction for the bonding e-
- partially (+) or partially (-)
- 0.4 < EN < 1.7
Electronegativity (EN)
ability/strength of atom to attract e-
- increase left–>right, bottom–>top
Polar molecule
separation of (+) and (-) charges in molecule
- unequal pull
dipole
2 electrical charges of = magnitude but opposite sign separated by distance
dipole moment (μ)
2 equal & opposite charges (Q+/Q-) separated by distance (r)
- μ = Qr
- Unit (μ) = D
Formal charge =
= (# v.e. atom brings) – (# e- surrounding on LS)
Resonance structures
1 LS can’t accurately depict molecule
- Need multiple LS
- ex: Ozone (O3)
Bond angles
angles made by lines joining nuclei of atoms
Valence-Shell Electron-Pair Repulsion Model:
Electron pairs repel each other
- best arrangement = minimizes repulsions
region e- most likely to be found
bonding pair
Hypervalent
more than octet of e-
- break octet rule
Bond dipole
dipole moment w/ 2 atoms
- Bond dipole and dipole moments = vector quantities
- must consider 3D shape
nonpolar bond dipole
equal/opposite bond dipoles = symmetric
- Linear
polar bond dipole
bent in nature = asymmetric
- Overall dipole moment = up/towards
O (partial -) away H (partial +)
Valence-bond theory
“overlap” of orbitals
- Sharing of space b/w 2 e- of opposite spin = covalent bond
- share space b/w nuclei
Hybrid orbitals
“mixing” of 2+ atomic orbitals on the same atom
degenerate orbitals
“new orbitals” after hybridization
- 2 orbitals mix –> create 2 orbitals
- 6 e- start –> 6 e- end
Orbital Shape
orbitals in bonded molecules (molecular orbitals) have diff shape an unbonded atom (atomic orbitals)
Orbital Energy Level
energy level changes from atomic molecular
Sigma (σ) bond
to-head overlap (direct collision @ end points) ; forms covalent bond
- cylindrical symmetry of e- density about nuclear axis
Pi (∏) bond
sideways overlap of p orbitals
- e- density above and below nuclear axis
- ALWAYS involves p orbitals
localized electrons
σ, ∏, lone pair:
- Bonding e- shared only b/w 2 atoms
delocalized electrons
∏, lone pair:
- Bonding e- shared by 3+ atoms
- Due to Resonance!
largest lattice energy magnitude
large charge + small ion
ionic size increases…
from top to bottom (right to left)
polarity is based on
electronegativity
acid in Lewis Structure
O-H
average bond order =
(# of bonds)/(# of bonding domains)
hybridization =
ED # - 1 (ex: N = 4 ED = sp3)
zero dipole moment
nonpolar
- equal pull
nonzero dipole moment
polar
- unequal pull
When to subtract from bond angles?
1 lone pair = -2 degrees
an atom with low first ionization energy and low electron affinity is more likely to form a ___.
more like to form a cation (than an anion)
T/F: the most common ion for an atom of a representative element generally adopts a noble-gas electron configuration
true
the stability of KBr is due to the _______ between the potassium ions and the bromide ions
electrostatic attraction
the attraction b/w cations and anions increases as the ___ increase.
charges on the ions
the attraction b/w cations and anions decreases as the ___ increase.
radii of the ions
what happens to electron density as you increase the distance between nuclei in a covalent bond?
- repulsions in nuclei decrease
- attraction b/w nuclei and e- decrease
- repulsions b/w e- = unaffected
cations
(+), metal, smaller radius
anions
(-), nonmetal, larger radius
strength of a bond increases, as # of __ increase
e-
- ex: H2 > H2+
electron affinity vs electronegativity
electron affinity- energy released when 1 atom gains an e- to form a (1-) ion
electronegativity- ability of atom to attract e-
- no units
electron affinity vs electronegativity
- electron affinity- energy released when 1 atom gains an e- to form a (1-) ion
- electronegativity- ability of atom to attract e-
- no units
elements w/ high EN, usually also have high ____
first ionization energy and electron affinity
Benzene:
{circles inside of hexagon}
- circle = 3 double bonded C (w/ resonance- 1 single)
- vertices on hexagon = 1 carbon atom
- H atoms = omitted
- notation = blend of 2 = resonance structures
reaction enthalpy can be estimated by:
- energy added to break bonds + energy released forming bonds
avg bond enthalpies
- Energy to break bonds
- More bonds = more energy to break
- # of bonds ↑, bond length ↓, bond enthalpy ↑
dipole energy/direction of arrow is based on ___
Electronegativity
in valence bond theory, bonds are formed by the overlap of ___
atomic orbitals in different atoms
as two atoms are pulled apart, the overlap between their atomic orbitals ___
decreases
bond order =
1/2 (# bonding electrons - # nonbonding electrons)
(*) =
antibonding molecular orbital
paramagnetism
more unpaired e- = stronger attractive force
diamagnetism
no unpaired e- = weakly repelled by magnetic field
SO3 is polar or nonpolar?
polar
IF5 is polar or nonpolar?
polar
PCl3 is polar or nonpolar?
polar
XeF4 is polar or nonpolar?
nonpolar
- octahedral ; square planar
partial charge for diatomic molecules
partial = (Formal Charge on atoms of interest) / (# of atoms of interest)
- ex: NO3
partial charge for diatomic molecules
partial = (Formal Charge on atoms of interest) - (# of atoms of interest)
- ex: NO3
- (-1 + -1 + 0) / (3)
sulfuric acid
H2SO4
acetic acid
CH3COOH
perchloric acid
HClO4
