bonding and structure Flashcards
what is ionic bonding?
ionic boding is the strong electrostatic attraction between two oppositely charged ions.
what are the to factors affecting ionic bonding?
ionic charges and ionic radii.
what are the physical properties that prove the theory of ionic bonding.
- high melting points.
- soluble in water but not in non polar solvents
- ionic compounds don’t conduct electricity when they are a solid but do when they are molten or dissolved
- ionic compounds cant be shaped- ionic compounds are brittle.
what evidence is there for charged particles?
the migration of ions.
when you electrolyse a green solution of copper(II) chromate(VI) on a piece of wet filter paper the filter paper turns blu at the cathode and yellow at the anode.
what is a covalent bond?
a covalent bind is the string electrostatic attraction between the two positive nuclei and the shared electrons in the bond.
wha is the bond enthalpy?
the bond enthalpy is related to the length of a bond. as the two positive nuclei repel each other as well as being attracted to the electrons it means that the bond has to be a certain length in order to balance these forces. the higher the electron density (the more electrons in the bond) the shorter the bond will be and so the higher the bind enthalpy.
what is dative covalent bonding?
dative covalent bonding is where both electrons in the bond come from one atom.
what is the difference between electrons that will affect the bond angles?
a lone pair with another lone pair will give the biggest bond angle.
a lone pair with a bonded pair will give the second biggest
a bonded pair with a bonded pair will give the smallest bond angle.
what is the name and bond angle form a molecule with two pairs of electrons?
linear- 180
why can silicon and carbon each form giant covalent structures?
they can both bond to 4 other atoms.
why can graphite conduct electricity?
it is made out of sheets of carbon atoms. these carbon atoms each have their 4th electron fairly free to move between the sheets.
what is graphene?
graphing is one layer of graphite. like graphite it can conduct electricity and is very strong. it is also transparent and light.
what is electronegativity?
the ability of an atom to attract the bonding electrons in a covalent bond.
where does electro negativity increase?
across the period and up the groups.
what affect des ionic charge have in ionic binding?
the greater the charge on the ion the strong the ionic bonding therefore the higher the boiling point
how does the ionic radii affect the ionic bonding?
smaller ions can pack closer together than larger ions. electrostatic ions gets weaker with distance, so small, closely packed ions have stronger ionic bonding than larger ions. then ions with a smaller radii have a higher boiling point
what is bind energy related to?
the length of the bond. in covalent molecules ti positive nuclei are attracted to the are of electron density between the two of them. however the two positively charged nuclei also repel each other as do the electrons so to maintain the covalent bonds these forces have to be balanced.
the higher the electron density, the stringer the attraction, the higher the enthalpy.
what does the molecular shape spend on?
the shape of the molecule depends on the electron pairs around the central atom. Electron pairs repel each other as much as they can. the type of electron pair affects how much it repels (lone pairs repel more)
how do polar and non-polar binds form?
in covalent bonding the electrons sit in orbital between the nuclei. if both the atoms have the same or similar electronegativities then the electrons will sit midway between the two and the bond will be non-polar.
if the atoms have different electro negativity then the bond will be polar as the electrons will be pulled toward the atom with the greater electronegativity giving each atom a potential charge
how do you use the pauling scale to work out the percentage ionic character?
you can use electronegativity to predict the type of bind that will form between atoms - the higher the difference in electronegativity the more ionic a bond is - a table will be given showing the electron negativity difference and the % ionic character
what foes the polarity of a molecule depend on?
it depends on the shape of a molecule and the polarity of the bond. it has to have an overall dipole.
what are London forces?
they are also called instantaneous dipole dipole bonds and they cause all atoms to be attracted to each other.
electrons are always moving quickly, at any one moment they are more likely to be on one side than the other, at this point the atom would have a temporary dipole. these london forces can hold molecules in a lattice
why do stronger london forces form and what does this mean?
larger molecules have larger electron clouds and therefore a higher electron density and so they have stronger london forces - also i they have a bigger surface area their electron cloud will be more exposed and so they will have stronger London forces
the stronger the bond the more energy is required to overcome it.
what are permenant dipole - perenant dipole bonds?
the potential charges in polar molecules cause weak electrostatic forces if attraction between molecules.
they happen as well as London forces
when does hydrogen bonds form?
they only occur the hydrogen in covalently bonded to fluorine, nitrogen or oxygen - they have a very high electronegativity so they draw the bonding electrons away from the hydrogen
how do hydrogen bonds affect the boiling points of HF?
molecules of HF form hydrogen bonds with each other - very difficult to overcome therefore HF has the highest boiling point
how does hydrogen bonding affect water?
if you look at the trend of the group 7 hydrides it is similar t the trend of Group 7 hydrides waters ability to form hydrogen bonds with itself gives it a higher boiling point.
how dos hydrogen bonds explain why ice floats on after
in ice the water molecules are arranged so that there is a maximum number of hydrogen bonds - the lattice structure caused by this leaves lots of space - this means that ice is much less dense than water so it floats
what happens to alkanes as they increase in length?
there boiling point increases as the surface area that is exposed is greater so stronger london forces can form because there is more molecular surface contact
why are alcohols less volatile than similar alkanes.
they contain a polar hydroxyl group meaning that hydrogen bonds form between the molecules
what happens when alkanes are branched?
they can’t pack as close together and their molecule surface contact is small compared to straight chain alkanes so fewer london forces can form
what is solubility affect by?
bionding.n for a substance to dissolve in another the bonds have to break, bonds in the solvent have to break and new bonds have to break between the solvent and the and the substance.
what are the two types of solvent?
polar and non-polar.
polar solvents are made up of polar molecules
Non-polar solvents such as hexane form london forces
what solvents do ionic substances dissolve in?
polar solvents such as water. when ionic substances mix with it the ions are attracted to opposite ends of the water molecule, the ions are pulled away from the ionic lattice, by water molecules which surround the ions. this process is called hydrations
what do alcohol dissolve in?
polar solvents such as water. because the polar OH bond in alcohols is attracted to the polar OH bond in water hydrogen bonds form between the lone pairs on the oxygen atoms and the hydrogen atoms. the carbon chain is not attracted to water so the more carbons that there are the less soluble it will be
why do not all mol;eccles with polar bonds dissolve in water?
fro example halogen alkanes contain polar bonds but their dipoles are nit strong enough to form hydrogen bonds
what do non-polarr substances dissolve best in?
non-polar solvents - like dissolves like (usually) - similar intermolecular forces.
how do the properties of giant structures provide evidence for covalent bonding?
they have v.high melting points - a lot of energy is required to break a lot of strange bonds
v.hard - vey strong bonds through a lattice arrangement
good thermal conductors - vibrations travel easily through stiff latices
insoluble - more attracted to labours than solvent molecules
can’t conduct electricity
what is bind energy related to?
the length of the bond. in covalent molecules ti positive nuclei are attracted to the are of electron density between the two of them. however the two positively charged nuclei also repel each other as do the electrons so to maintain the covalent bonds these forces have to be balanced.
the higher the electron density, the stringer the attraction, the higher the enthalpy.
what does the molecular shape spend on?
the shape of the molecule depends on the electron pairs around the central atom. Electron pairs repel each other as much as they can. the type of electron pair affects how much it repels (lone pairs repel more)
how do polar and non-polar binds form?
in covalent bonding the electrons sit in orbital between the nuclei. if both the atoms have the same or similar electronegativities then the electrons will sit midway between the two and the bond will be non-polar.
if the atoms have different electro negativity then the bond will be polar as the electrons will be pulled toward the atom with the greater electronegativity giving each atom a potential charge
how do you use the pauling scale to work out the percentage ionic character?
you can use electronegativity to predict the type of bind that will form between atoms - the higher the difference in electronegativity the more ionic a bond is - a table will be given showing the electron negativity difference and the % ionic character
what foes the polarity of a molecule depend on?
it depends on the shape of a molecule and the polarity of the bond. it has to have an overall dipole.
what are London forces?
they are also called instantaneous dipole dipole bonds and they cause all atoms to be attracted to each other.
electrons are always moving quickly, at any one moment they are more likely to be on one side than the other, at this point the atom would have a temporary dipole. these london forces can hold molecules in a lattice
why do stronger london forces form and what does this mean?
larger molecules have larger electron clouds and therefore a higher electron density and so they have stronger london forces - also i they have a bigger surface area their electron cloud will be more exposed and so they will have stronger London forces
the stronger the bond the more energy is required to overcome it.
what are permenant dipole - perenant dipole bonds?
the potential charges in polar molecules cause weak electrostatic forces if attraction between molecules.
they happen as well as London forces
when does hydrogen bonds form?
they only occur the hydrogen in covalently bonded to fluorine, nitrogen or oxygen - they have a very high electronegativity so they draw the bonding electrons away from the hydrogen
how do hydrogen bonds affect the boiling points of HF?
molecules of HF form hydrogen bonds with each other - very difficult to overcome therefore HF has the highest boiling point
how does hydrogen bonding affect water?
if you look at the trend of the group 7 hydrides it is similar t the trend of Group 7 hydrides waters ability to form hydrogen bonds with itself gives it a higher boiling point.
how dos hydrogen bonds explain why ice floats on after
in ice the water molecules are arranged so that there is a maximum number of hydrogen bonds - the lattice structure caused by this leaves lots of space - this means that ice is much less dense than water so it floats
what happens to alkanes as they increase in length?
there boiling point increases as the surface area that is exposed is greater so stronger london forces can form because there is more molecular surface contact
why are alcohols less volatile than similar alkanes.
they contain a polar hydroxyl group meaning that hydrogen bonds form between the molecules
what happens when alkanes are branched?
they can’t pack as close together and their molecule surface contact is small compared to straight chain alkanes so fewer london forces can form
what is solubility affect by?
bionding.n for a substance to dissolve in another the bonds have to break, bonds in the solvent have to break and new bonds have to break between the solvent and the and the substance.
what are the two types of solvent?
polar and non-polar.
polar solvents are made up of polar molecules
Non-polar solvents such as hexane form london forces
what solvents do ionic substances dissolve in?
polar solvents such as water. when ionic substances mix with it the ions are attracted to opposite ends of the water molecule, the ions are pulled away from the ionic lattice, by water molecules which surround the ions. this process is called hydrations
what do alcohol dissolve in?
polar solvents such as water. because the polar OH bond in alcohols is attracted to the polar OH bond in water hydrogen bonds form between the lone pairs on the oxygen atoms and the hydrogen atoms. the carbon chain is not attracted to water so the more carbons that there are the less soluble it will be
why do not all mol;eccles with polar bonds dissolve in water?
fro example halogen alkanes contain polar bonds but their dipoles are nit strong enough to form hydrogen bonds
what do non-polarr substances dissolve best in?
non-polar solvents - like dissolves like (usually) - similar intermolecular forces.
how do the properties of giant structures provide evidence for covalent bonding?
they have v.high melting points - a lot of energy is required to break a lot of strange bonds
v.hard - vey strong bonds through a lattice arrangement
good thermal conductors - vibrations travel easily through stiff latices
insoluble - more attracted to labours than solvent molecules
can’t conduct electricity
what are the different structure that are formed by carbon atoms
diamond
graphite
graphene - one layer of graphite
what do physical properties depend on?
they depend on the nature of the particles - boiling point depends on the attraction between molecules, only conduct energy if its charged particles are free to move
