3 Bonding Flashcards
why do chemical bonds form
to achieve a more stable electron arrangement
when are ionic bonds formed
when one or more electrons are tranferred from one atom to another
what holds ions together
electrotatic attraction
what do groups in the periodic table to form ions
group1 loses 1 electron forming a +1 ion group2 loses 2 electrons forming +2 ion group3 loses 3 electrons forming 3+ ion group4 gains 3 electrons forming 3- ion group5 gains 2 electrons forming 2- ion group 7 gains 1 electron forming 1- ion group8 dont gain or lose electrons to form ions
what is the formula for a sulphate ion
SO4 2-
what is the formula for a hydroxide ion
OH-
what is the formular for a nitrate ion
NO3-
what is the formula for a carbonate ion
CO3 2-
what is the formular for an ammonium ion
NH4+
define a giant lattic
giant regular arrangement
explain why ionic compounds conduct electricty when they’re moletn or dissolved but not when solid
the ions are free to move to carry a charge in a solid all the ions are in fixed position by strong ionic bonds
explain why ionic compounds have high melting points
a lot of energy is needed to break the strong ionic bond between the oppositely hcarged ions
explain why ionic compunds dissolve in water
water molecules are polar they have a partially positive charge part and partially negative charged part these charged parts pull ions away from the lattice causing it to dissolve
give two examples of ionic compunds
NaCl
MgCl2
when do molecules form
they form when two or more atoms bond together it doesnt matter if the atoms are the same/different
how does sharing electrons hold atoms together
the electrons are held by electrostatic aqttraction between the nuceli and the shared electrons this takes place within the molecule
what is a covalent bond
a shared paired of electrons forms when two or more orbitals overlap
is the electrostatic attraction between the positive nucleus of an atom and the bonded pair of electrons
between what type of atoms do covalent bonds form
non metals
what is a dative /co ordinate bond
where the dative bond contains a shared pair of electrons with both electrons supplied by one atom.
why does dative bonding occur in ammonium ions
becvause it forms when the nitrogen atom in an ammonia molecule donates a pair of electrons to a proton H+
how do you represent a dative bond in diagrams
and arrow pointing away from the ‘donor’ atom
give another name for giant covalent structures
macromolecular structures
what is a giant covalent structure
a huge network of covalently bonded atoms
give to examples of giant covalent structures
diamond and graphite
why can graphite be used as a lubricant and be used in pencils
the week van der waals forces between the layers of graphite eare easily broken so the layers can slide over each other
descirbe the structure of and bonding in graphite and explain why the melting point of graphite is very high
the layer of carbon atoms are connected by covalent bonds within each layer there are weak van der waals forces between the layer.A lot of energy is needed to break the strong covalent bonds s
explain why can graphite conduct electricity
the delocalised electrons in grahite are not attached to any carbon atoms and are free to move along the sheets carrying a charge
explain why is graphite is insoluble in any solvent
the covalent bonds in the sheets are too strong to break
explain why graphite can be used to make strong lightweight sports equipment
the layers are far apart vompared to the length of the covalent bonds so graphite has a low density
explain what property makes diamond useful in diamond tipped drills and saws
property:hard ,diamond has a strong unlayered rigid 3D structure held be strong covalent bonds
explain why diamond cannot conduct electricity
diamond has no free delocalised electrons to carry charge as all the outer electrons are held in localised bonds
explain why is diamond is insoluble in any solvent
the covalent bonds in diamonds 3D structure are too strong to break
explain why diamond is a good thermal conductor
vibrations travel easily through the stiff lattice
why does diamond sparkles when you cut it
its structure makes it refract light a lot
describe the bonding in a crystal of iodine
covalent bonds between the atoms
name the crytsal tyep which describes an idoine crystal
molecular strcutre
explain why heat energy si required to melt an iodine crytssla
the weak van der waals forces must be broken
explain why iodine vaporiesses when heated gently
the weak van der waals forces between the iodine molecules are easily broken
why doesnt iodine conduct electricity
because there are no charged aprticles to carry charge
explain why iodine has a low boiling boint
he weak van der waals forces between the iodine molecules are easily broken
describe the bonding in a metal
lattice of poisitve ions embedded in a sea of delocalised electrons
explain why metals have a high metling point
a lot of energy is needed to break the strong metallic bond
explain why magnesium has a higher melting poitn than sodium
magnesium has more protons which attracts the electrons more stronlgyh and so increasing the strength of the mettalic bond requiring more energy to break than the energy reuqired to break the metallic bond of soidum
explain why metals can conduct electriciyt
the delcoaised electrons can move to carry a charge through the metallic structure
explain why metals are thermal conductors
the delocalised electrons can pass kinetic negery to each other
explain how the charge of an ion affects the strenght of metals
the greater the charge on the ion the greater the number of delocaised electrons and the stronger the electrostatic attraction between the positive ions and the electrons and the stronger the metallic bond
explain how the size of an ion affects the strength of metals
the smaller the ion the closer the electrons are to the positive nucelsu and the stronger the metallic bond
explain why metals are ductile
the layers in the metal can slide over one another
explain hwy metals are malleable
after a small distortion each metal ion is in the same environemnt as before keeping the fixed arrangemtn of the metallic structure
explain why ionic compunds are brittle
s mall displacement will cause contatc between ions with like charges and so they repel casuing the ionic compound to shatter
what are the two rules that must happen for dative bonding to occur
the atom that accepts the electron pair is an atom that doesn’t have a filled outer main level of electrons
the atom that is donating the electrons has a pair of electrons that is not being used in a bond called a lone pair
deine elecotrnegativyt
it is a measure of an atms ability to attract a pair of electrons in a covalent bond
explain and state the trend in negativity going down a group
electronegativty decreases because there is more shieling by electrons which increases the atomic raduis and so the electrostaic force of attrcation decreases
explain and state the trend in negativity across a period
electronegativity increases because although shieklignis the same nucklear chasrge increases which decreases the atomic raduis and so the electrostaic force of attraction increases
what does electron density describe
describes the wy the negative charge is distributed in a molecule
deine polarity of covalent bonds
unequl sharing of electrons between atoms that are bonded together covalently
why is the covalent bond non polar between two atoms that are the same
the covalent bond is equally shared between the atoms since both atoms have the same electronegativty so the bond is completely non polar
why is the covalent bond polar between two different atoms
the bond will not be shared equally since the atoms have different electronegativy
In hydrogen fluroide why is fluroine end of the molecule relaitively negative and the hydrogen end relatively positive
hydrogen has a lower electronegativity than fluroine meaning the electrons in the covalent bond will be attrcated more by fluorine than hydrogen and so the electron cloud is distortewd towards fluroine making the flourine ened of the molecule relatively negative and the hydrogen end of the molecule relaitvely positive
what is the relationship between diffrence in electroneativity and polairty of a covalent bond
the bgretaer the diffrenece in electronegative the more polar the covalent bond is
list the different ytpes of intermolecular forces in order of strength
Van der walls forces
dipole-dipole forces
hydrogen bonding
where do van der waals forces occur
between all atoms and molecules that are non polar
why does I2 have a higher boiling point than CL2
iodine has more electrons than chlorine so the van der waals force of iodine is stronger and larger than the van der waals forces of chlorine and so more energy is needed to break the van der waals forces between the iodine molecules than the chlorine molecules
explain why straight chain alkanes have higher melting point than branched chain alkanes
staright chain alkanes can pack closer together than branched alkanes creating more points of contact between the moleculestherefore straight chain alkanes have stronger van der waals forces than branched chain alkanes and so require nore energy to break the van der waal forces between the molecules.
where do dipole - dipole forces occur
between molecules that have a polar bond
how do dipole dipole forces occur in hydrogen chloride
chlorine is more electronegative than hydrogen so electrons are pulled towards chlorine rather than hydrogen thefore molecule forms a dipole with paritally poisitve hyfdrogen and partially negative chlorine
how will two molecules with dipoles attarct one another
whatevere the starting position the molecules with dipoles will flip to give an arrangement where two molecules attract
when does hydrogen bonding occur
acts when hydrogen of one molecule is attracted to a more electronegative atom on a neigbouring molecule can only occur if the hydrogen is bonded to Fluroine,Oxygen,Nitrogen.
why does hydrogen bonding only occur between fluroine oxygen and nitrogen
because F,O,N are the only atoms electronegative eneough to form hydrogen bonds
how do we represent hydrogen bonds
— (dashes)
why is water polar
oxygen is more electronegative than hydrogen
why do the noble gases show a gradual increase in boiling points down the group
because the strength of van der waal forces acting between the atoms increases due to more electrons and so increases the strength and size of the van der waals forces down the group and so more and more energy is needed to break the van der waals forces
explain why the boiling points of water,hydrogen fluroide and ammonia all higher than the other hydrides of the other elements in their group
because hydrogen bonding is present between the molecules in each of the compounds (water,hydrogen fluroide and ammonia) so more energy is needed to break the hydrogen bonding than that of the intermolecular forces between the hydrides.
although phosphine molecules,Ph3 contain hydrogen atoms hydrogen bonding doesnt occur sugeest a reason why
Phosphoruos and hydrogen have a small electronegativity difference and P is not very electronegative
explain the importance of hydrogen bonding in ice
as liquid water cools to form ice the molecules make more hydrogen bonds and arrange themselves into a regular lattice structure where the water molecules are further apart on aergae than the molecules in liquid water so ice is less dense than liquid water and so ice forms on top of ponds rather than the bottom insulating the pond and enabling the life of organisms to evolve.
explain the importance of hydrogen bonding in ironing
the iron provides heat to break the hydrogen bonds in th crumpled material and pressure to make the material flat forcing molecules into new positions.When you remove the iron the hydrogen bonds can reform and hold the molecules in these new positions keeping the fabric flat.
What does the electron pair repulsion theory state
- pairs of electrons repel each other so they they are as far apart as possible
- lone pairs repel slightly more than bonded pairs because they’re more compact
- the molecule or ion takes up a shape which minimises these repulsions
- each lone pair reduces the bond angle by 2.5 degrees
How to draw a bond in the plain of the paper
a line
How to draw a bond coming out of the paper
a wedge
How to draw a bond going into the paper
a dotted line
what shape is a molecule with 2 electron pairs and no lone pairs and what is the bond angle
linear
180
what shape is a molecule with 3 electron pairs and no lone pairs and what is the bond angle
trigonal planar
120
what shape is a molecule with 4 electron pairs and no lone pairs and what is the bond angle
tetrehedral
109.5
what shape is a molecule with 4 electron pairs and one lone pair and what is the bond angle
trigonal pyramid
107
what shape is a molecule with 4 electron pairs and two lone pair and what is the bond angle
bent
104.5
what shape is a molecule with 5electron pairs and no lone pairs and what is the bond angle
trigonal bipyramid
120 and 90
what shape is a molecule with 5 electron pairs and one lone pairs and what is the bond angle
seesaw
102 and 87
what shape is a molecule with 5 electron pairs and two lone pairs and what is the bond angle
T shaped
88
what shape is a molecule with 6 electron pairs and no lone pair and what is the bond angle
octahedral
90
what shape is a molecule with 3 electron pairs and two lone pairs and what is the bond angle
square planar
90
describe the steps for predicting the shape of a molecule
- work out which one is the central atom
- use the periodic table to work out the number of electrons in the outer shell of the central atom
- add one to this number for every atom that the central atom is bonded to
- divide by two to find the number of electron pairs on the central atom
- compare the number of electron pairs to the number of bonds to find the number of lone pairs and bond pairs on the central atom
describe the steps for predicting the shape of an ion
- work out which one is the central atom
- use the periodic table to work out the number of electrons in the outer shell of the central atom
- add one to this number for every atom that the central atom is bonded to
- add one for each negative charge on the ion or subtract 1 for each positive charge on the ion
- divide by two to find the number of electron pairs on the central atom
- compare the number of electron pairs to the number of bonds to find the number of lone pairs and bond pairs on the central atom
Why does the shape of a molecule change when a coordinate bond forms
Bond pairs repel less than lone pairs so bond angle increases slightly
list the following in order of increase repulsion
lone pair-bond pair,lone pair-lone pair,bond pair-bond pair
bond pair-bond pair
lone pair -bond pair
lone pair-lone pair
what is the effect of lectron pair repulsion on bond angles
bond pair-bond pair angles are the smallest
lone pair-bond pair angles are the second biggest
lone pair-lone pair angles are the biggest
describve the physical properties of a solid
particles are very close together
solids cannot be compressed
particles vibrate about a fixed point and cannot move freely
describe the physical properties of a liquid
particles are still quite close together but not as much in solids
lquids cannot be compressed
particles move about freely and randomly within the liquid allowing it to flow
describe the physical properties of a gas
particles are far apart
can be compressed
particles move about freely and rapidly with a lot of energy
describe what happens when you heat a solid
particles vibrate more about a fixed point distance between the particles slightly increases so solid expands
describe what happens when you melt a solid into a liquid (melting-fusion)
energy is supplied to weaken the forces that act between the particles holding them toegtehr in the solid state
describe what happens when you heat a liquid(
you supply more energy to the particles increasing the KE of the particles the particles move a little further apart and so the liquid expands
describe what happens when you turn a liquid into a gas (boiling - vapourisation)
enegry is needed to break all the intermolecular forces between the particles
describe what happens whne you heat a gas
the particles gain KE and move faster the particles get much further apart and so the gas expands
