topic 2 Flashcards
what is ionic bonding
oppositley charged ions held together by electrostatic attraction
how to work out ionic formula
write two ions
Ca 2+ NO3 -
swap charges
Ca - NO3 2+
drop charges
Ca (NO3)2
simplify
Ca(no3)2
what are the properties of ionic bonds
most disolve in water - polar
conduct electricity when molten or disolved - ions free
brittle, layers slide, positive aligned with positive, repel
high mp, strong electrostatic forces
what affects the strength of an ionic bond
size of the charge
- bigger charge = stronger electrostatic attraction
- more energy
size of ion
- smaller ion = stronger electrostatic attraction
- ions can pack together more closley
- more energy
what happens to ionic radius down a group and why
increases
number of shells increases
what are isoelectric ions
diffferent atoms that have same number of electrons
what happens to the ionic radius of isoelectric ions ar atomic number increases and why
decreases
more protons pulling electron shells
what evidence is there for charged oartickes including colours and ions
electrolysis of copper (II) chromate (VI) on wet filter paper - green
positive Cu 2+ ions move towards -ve cathode - blue
negative CrO4 2- ions move towards +ve anode - yellow
what is covalent bonding
sharing of outer electrons to obtain a full shell
electrostatic attraction between shared electrons and +ve nucleus
what is a dative bond
one atom dontates 2 electrons
draw the bonding in NH4
see covalent bonding flash card
how do bond enthalpy and bond length link
shorter bond = higher bond enthalpy
what forces are there in covalent molecules and between what
forces of attraction - +ve nucleui and -ve electrons
repulsive forces - 2 +ve nuclei and between electrons of atom
what is bond length in terms of forces
balance between attractive and repulsive forces
what happens to the atrractive force, bond length and bond enthalpy when high electron density
stronger attraction
shorter bond length
higher bond enthalpy
what is the shape and angle in a moleucle when BP=2 and LP=0 with example and draw
linear
180
BeCl2
what is the shape and angle in a moleucle when BP=3 and LP=0 with example and draw
trigonal planar
120
BF3
what is the shape and angle in a moleucle when BP=4 and LP=0 with example and draw
tetrahedral
109.5
CH4
what is the shape and angle in a moleucle when BP=5 and LP=0 with example and draw
trigonal bipyramidal
90 and 120
PCl5
what is the shape and angle in a moleucle when BP=6 and LP=0 with example and draw
octahedral
90
SF6
what is the shape and angle in a moleucle when BP=3 and LP=1 with example and draw
trigonal planar
107
NH3
what is the shape and angle in a moleucle when BP=2 and LP=2 with example and draw
bent
104.5
H2O
what is the shape and angle in a moleucle when BP=3 and LP=2 with example and draw
distorted t
87.5
ClF3
what is the shape and angle in a moleucle when BP=4 and LP=1 with example and draw
seesaw
87 and 102
SF4
what is the shape and angle in a moleucle when BP=5 and LP=1 with example and draw
square pyramidal
81.5 and 90
IF5
what is the shape and angle in a moleucle when BP=4 and LP=2 with example and draw
square planar
90
XeF4
describe the structure and properties of diamond
each carbon bonded 4x in tetrahedral shape
heat conducts - tightly packed rigid arrangement
very high mp - strong covalent bonds
doesnt conduct electricity - no delocalised electrons
insoluble - covalent bonds too strong
decribe the structure and properties of graphite
each carbon bonded 3x with 4th electron delocalised
layers slide - weak forces between layers
conducts electricity - delocalised electrons between layers
low density - layers far apart
high mp - strong covalent bonds
insoluble - strong covalent bonds
decribe the structure and properties of graphene
1 layer of graphite
hexagonal carbon rings
conducts electricity - delocalised free moving electrons
high strength - delocalised electrons
light weight and transparent - one cell thick
what is metalic bonding
positive methal ions are formed as metals donate electrons to form sea of delocalised elctrons
electrostatic attraction between +ve metal ions and delocalised electrons
more elctrons an atom can dontae the higher the mp
what are the properties of metalic bonds
good thermal conductors - delocalised e- transfer kinetic energy
good electrical conductors - delocalised e- are mobile and can carry current
high mp - strong electrostatic attractions
insoluble - metalic bonds strong
malleable and ductile - ion layers can slide and still retain at5tractionw
hat is electronegativity
ability for an atom to attract electrons towarrds itself in a covalent bond
where are the most elecronegative elements on the periodic table
up and right
what scale measures electronegativity
pauling
how do ionic bonds and electronegativity link
biggger difference more ionic the compound
what is a polar bond
covalent bonds become polar if atoms have a difference in elecronegativity
eg HCl H2O
when are compounds not polar
same electronegativity
polar bond stmmetrical eg CO2
what are london forces
weakest intermolecular force
exist between atoms
ant molecule with electrons can form a dipole
temporary dipole when 2 molecules neare
electrons in one molecule can move from one end to another
who do london forces hold some molecules in crystal structure
iodine
weak london forced hold I2 molecules
strong covalent bonds hold the 2 atoms
what affects size of london force
size of atom
bigger = larger e- cloud = more london forces
what is a dipole dipole intermolecular force
exisit in molecules with polarity
eg HCl
what is the test for a dipole dipole
placing a charged rod near steadt stream of polar liquid
bend towards
what is a hydrogen intermoleular force
strongest
very electronegative elements
- hydrogen with nitrogen, oxygen or flurine
what differes in the hydrogen bonding of water and ice
ice forms a regular structure, the molecules are further apart making it less dense
why are alcohols not as volatile as alkanes
hydrogen bonding in alcohols
what solvents do polar molecules dissolve in
polar solvents
what must happen for a substance to dissolve
solvent binds must break
substance bonds must break
new bonds formed between substance and solvant
new bonds of same or greater strength
what is hydration and draw diagrams
water molecules surrond ion
see flash card
do alcohols dissolve
dissolve in polar solvants as they can hydrogen bond
hydrocarbon doesnt dissolve
bigger=less soluble
do haloalkanes dissolve
no as dipoles not strong
what are non polar substances and what dissolve in them
only have london force
alkenes dissolves as they can form london forces between molecules
