Studied by 0 people
what forces do all simple covalent molecules have
intermolecular
what 3 types of intermolecular forces are there
van Der walls, dipole-dipole, hydrogen
what is the weakest intermolecular force
van der walls
what forms a van der walls force
an instantaneous dipole due to electron distribution
why does electron distribution induce dipole
electrons repel
what can increase strength of van der walls
more electrons
what molecules have van der walls
all molecules
what forms a dipole-dipole force
permanent attraction between molecules due to electronegativity and bond polarity
what must the element be to have dipole-dipole
asymmetrical
why do symmetrical molecules not have dipole-dipole
polar bonds cancel out
what is the strongest type of inter molecular forces
hydrogen bonds
how strong are intermolecular forces
weak
what elements must be present for a hydrogen bond
hydrogen and fluorine, oxygen or nitrogen
what are hydrogen bonds
direct bonds with hydrogen and a highly electronegative element
does a lone pair affect hydrogen bonding
no
what angle must hydrogen bonds be drawn at
180 degrees
what is melting point affected by
strength of intermolecular bonds
define electronegativity
the ability of an atom to attract electrons in a covalent bond towards itself
which element has the highest electronegativity
Fluorine
which element is the least electronegative
Caesium
Name 3 factors which affect electronegativity
nuclear charge, atomic radius, shielding
define sheilding
the shells between the nucleus and outer electron
define non-polar
no difference between two elements in electronegativity
define polar
difference between two elements in electronegativity
what does delta positivity represent
the less electronegative element
what does delta negative represent
the more electronegative element
what can a difference in electronegativities induce
permanent dipole
what is the relationship between bonding and lone pairs
repulsion
what repulsion is stronger, lone-lone or bonding-bonding
lone-lone
shape: 2 bonding pairs
linear
linear bond angle
180
shape: 3 bonding
trigonal planar
trigonal planar bonds angle
120
shape: 4 bonding
tetrahedral
tetrahedral bonds angle
109.5
shape: 3 bonding, 1 lone
pyramidal
pyramidal bond angle
107
shape: 2 bonding, 2 lone
V or bent shape
V or bent shape bond angles
104.5
shape: 5 bonding
trigonal bypyramidal
trigonal by pyramidal bond angles
120 & 90
shape: 4 bonding, 1 lone
modified trigonal bypyramidal
modified trigonal bypyramidal bond angles
118 & 89
shape: 3 bonding, 2 lone
T shaped
T shaped bond angle
86
shape: 2 bonding, 3 lone
linear
linear (2bp, 3lp) bond angle
180
shape: 6 bonding
octahedral
octahedral bond angle
90
shape: 4 bonding, 2 lone
square planar
square planar bond angle
90
name the four types of crystal structures
ionic, metallic, macromolecular, simple molecular
what is a macromolecular structure
a giant covalent molecule
give 4 examples of physical properties
boiling point, melting point, solubility and conductivity
what mp and bp do ionic crystals have
high
why do ionic crystals have high mp and bp
electrostatic forces are strong and require a lot of energy to break
when can ionic crystals conduct
when molten or in a solution
why can ionic crystals conduct when molten
the ions are free to move and carry charge
are ionic crystals brittle
yes
why are ionic substances brittle
layers of ions repel breaking the lattice
why do atoms with more ions have a greater mp in ionic crystals
there are more electrostatic forces
can metals conduct
yes
why do metals conduct
the sea of electrons is free to move and carry charge
why are metals malleable
layers of positive ions are able to slide over each other
what state are metals normally at rtp
solid
what kind of melting point do metals have
high
why do higher charged ions have higher ups in metals
more protons means more electrons so stronger electrostatic forces
what forces hold simple molecules together
van der walls
are van Der walls in simple covalent molecules weak or strong
weak
what boiling/melting points does simple covalent molecules have
low
can simple molecules conduct
no
why can’t simple molecules conduct
there are no charged particles
what bonding does a macromolecule have
covalent
why do macromolecules have a high melting point
they have multiple strong covalent bonds
what structure has low melting points
simple molecular
what structure is diamond
macromolecular
how many covalent carbon-carbon bonds does diamond have
4
why is diamond so strong
it has 4 covalent carbon-carbon bonds
how many carbon-carbon bonds does graphite have
3
why can graphite conduct
is has free electrons which move between layers
why does graphite have free electrons
they’re not used in bonding
what is a positively charged ion called
cation
what is a negatively charged ion called
anion
what crystal structure is ice
simple molecule
what crystal structure is iodine
simple molecule
what crystal structure is magnesium
metallic
what crystal structure is sodium chlorides
ionic
what structure does metallic bonding take
a lattice
describe metallic bonded structures
a lattice of positively charged ions surrounded by a sea of delocalised electrons
what forces do metallic bonds have
strong electrostatic forces
what are the electrostatic forces between in a metallic bond
oppositely charged ions
what would a greater charge on the ions cause
a stronger attractive force
what would larger sized ions cause
weaker attraction due to atomic radius
why do metallic bonded chemicals conduct
because electrons are free to move
define coordinate bonding
both electrons in a covalent bond donate to one atom
what is dative covalent bonding
coordinate bonding
what groups are covalently bonded
group 4 5 6 7 8 non metals
what two elements can covalent bonds form between
non-metals
how can covalent bonds be shown
in dot and cross diagrams
what type of forces do covalent bonds have
strong electrostatic forces
Note 
Flashcard (32)