Chapter 3 Flashcards
exceptions to the octet rule
hydrogen, lithium-2
berrylium-4
boron- 6
period three and greater can have expanded octet
what elements always follow the octet rule
C, N, Na, F, Mg
ionic bond
transfer electrons from atom with low IE (metal) to high IE (non metal)
held by electrostatics and form lattice to maximize force
When are ionic bonds used
Difference of EN is greater than 1.7
Characteristics of ionic bond
strong, high BP/MP, dissolve in polar, good conductors
covalent bond
electron pair shared between atoms (non metals with similar EN)
electrons attract to positive nuclei
can be equal or unequal
Covalent bond characteristics
lower mp/bp
weaker
bond order
number of shared electron pairs between 2 atoms
bond length
distance between 2 nuclei
more bonds= increase electrostatic pull, decrease length
bond energy
energy required to break a bond
greater number of shared electrons means higher energy and stronger
polarity
differ in EN, differ in sharing
higher EN gets more electron density
non polar covalent
nearly identical EN share electrons and have equal distribution (no separation of charge)
EN difference is less than .5
polar covalent
share electrons unevenly, has separation of charge
EN difference between .5 and 1.7
EN atom has more electrons, partial negative
dipole moment
vector quantity
p=qd
q= charge, d= displacement
coordinate covalent bond
both of shared electrons are contributed by one of the atoms
lonepair attacks unhybridized p orbital
lewis acid and base
bonding electrons
electrons involved in covalent bond
formal charge
difference between number of valence electrons in lewis and number of valence in neutral atom
assumes equal sharing, underestimates EN
lewis structure
most stable form will minimize number and magnitude of formal charge
formal charge calculation
number of valence electrons in atom
sum to make total
FC= Valence- nonbonding -1/2 bonding
most stable lewis
contributes more to resonance
prefer small or no formal charge
prefer less separation between opposite charge
prefer negative on EN
VSEPR
uses lewis structure to predict molecular geometry
3D determined by repulsions
electron geometry
spatial arrangement of all electron pairs around center
bonding and lp
molecular geometry
spatial arrangement of only bonding pairs of electrons
coordination number
number of atoms that are surrounded and bonded to a central atom
molecular orbital
probability of finding the bonding electron in a given space formed when atomic orbitals interact into a compound
bonding vs. antibonding MO
bonding: same sign atomic orbitals
nonbonding is different signs
pi bond
overlap to have 2 parallel electron cloud densities
no rotation, parallel
sigma bond
head to head overlap, can rotate freely due to single and linear nature
intermolecular forces
keep substance together, electrostatic interactions
dispersion < dipole < hydrogen
Dispersion/ Van Der Walls
temporary dipoles causing interactions due to random unequal electron distribution
negative causes attraction to other positive when proximal
occurs more in larger molecules
dipole- dipole
opposite ends of polar molecules attract with other dipoles
Not in gas (too far)
in polar, increases MP/BP
hydrogen bonds
strong dipole
can be intra or intermolecular
hydrogen with EN atom will act as a proton and interacts with negative nearby such as F,O,N
increases BP
