Unit 4 - Bonding

Intramolecular (covalent, ionic, metallic) and intermolecular forces IMF (hydrogen, van der waal's)

intramolecular forces

covalent, ionic, metallic

intermolecular forces

hydrogen, van der waal's (london + dipole-dipole)

intra vs. inter

intra is between atoms, inter is between molecules

covalent bond

a bond between two anions (nonmetals) where two electrons are shared

ionic bond

a bond between a cation (metal) and an anion (nonmetal) where an electron is transferred

metallic bond

an electrostatic attraction between the positively charged nuclei and a sea of delocalized electrons

structure of ionic compound

lattice structure

structure of metallic compound

lattice structure

alloy

mixture containing two or more metals, have enhanced properties

strength of a metallic bond depends on...

# of valence electrons that can become delocalized, the charge of the metal ion, and the ionic radius of the cation

more delocalized electrons =

stronger metallic bond

greater positive charge on a metal ion =

stronger metallic bond

smaller ionic radius on a metal ion =

stronger metallic bond

alloys have...

greater strength, enhanced magnetic properties, and greater ductility

transition metals can form more than one cation because...

they have partially filled d-orbitals

difference in EN greater than or equal to1.8 =

ionic bond

difference in EN less than 1.8 =

covalent bond

as bond length decreases...

bond strength increases, therefore it takes more energy to break the bonds

difference in EN between 0.4 and 1.7 =

polar covalent

difference in EN less than 0.4 =

nonpolar covalent

VSEPR

valence shell electron pair repulsion theory: a molecule's 3-D shape is determined by repulsion between bonding and non-bonding electron pairs

tetrahedral

109.5

bent (2 bonds, 2 lone pairs)

104.5

trigonal pyramid

107.8

bent (2 bonds, 1 lone pair)

109.5 < x < 120

trigonal

120

linear

180

coordinate covalent bond

one atom donates both e- (the pair) to the bond

allotrope

different forms of the same element in the same physical state

carbon allotropes

diamond, graphite, graphene, C-60 fullerene

diamond

non-conductor, bonded to 4 other carbon atoms (tetrahedral), extremely high melting point

graphite

conducts electricity bc of delocalized electrons, bonded to three other carbon atoms (trigonal planar), good lubricant bc weak bonds (london) between layers

graphene

a single sheet of graphite, bonded to 3 other carbons, super conductor

C-60 fullerene

spherical arrangement of 60 carbon atoms, each c bonded to 2 other c's , has delocalized electrons, does not conduct electricity bc it is a closed shape

structure and bonding of silicon dioxide SiO2

each Si is bonded to four oxygen atoms ; tetrahedral, 109.5, high melting point and nonconductive

electronegativity

the attraction between a pair of covalent bond electrons and a positively charged nucleus

dipole movement

the difference in partial charge

all diatomic molecules are...

nonpolar

if the difference between the electronegativity values of two elements is

the compound is nonpolar covalent

if something is polar, it has more...

intermolecular stickiness = stronger IMFs

are IMFs or intramolecular forces stronger?

intramolecular forces are stronger

bond polarity of a molecule depends on both...

its shape (VSEPR) and the electronegativities of its atoms

intermolecular forces are...

the electrostatic attractive forces between molecules (not atoms) that holds molecules together

van der waal's forces

weakest - london dispersion, dipole-dipole

london dispersion

temporary dipole bc of unequal spread of electrons, ALL molecules have some form of london dispersion

london forces increase with...

more electrons, increasing mass of molecules

dipole-dipole

permanent dipole, electrostatic attraction between two polar molecules containing a dipole

if a molecule has dipole-dipole forces...

it is polar

nonpolar molecules only have...

london dispersion

hydrogen bonding

a special type of dipole-dipole bonding with two O-H dipoles (strongest IMF), H has to be bonded with FON

factors leading to increased boiling point

more london dispersion, more hydrogen bonding

covalent compounds typically have a lower melting point than...

ionic compounds

large network covalent structures i.e. diamond + silicon dioxide have...

extremely high melting and boiling points

IMF order of boiling points from lowest to highest

london < dipole-dipole < hydrogen

intramolecular forces order of boiling points from lowest to highest

nonpolar < polar < ionic < network covalent

what must be broken to change phase?

IMFs

why are metals malleable

bc electrons are delocalized and move more w/ no repulsion

ionic compounds are...

brittle

metals are...

good conductors, stronger than ionic, malleable, ductile, high boiling/melting point

covalent compounds are...

nonconductive, low melting/boiling point

alloys have...

reduced malleability, more rigid = higher strength