Studied by 32 people
what is ionic bonding?
ionic bonding involves electrostatic attraction between oppositely charged ions in a lattice.
what is the formula of a sulfate ion?
SO₄²-
what is the formula of a hydroxide ion?
OH-
what is the formula of a nitrate ion?
NO3-
what is the formula of a carbonate ion?
CO32-
what is the formula of an ammonium ion?
NH4+
what is a single covalent bond?
it contains a shared pair of electrons, multiple covalent bonds contain multiple pairs.
what does ionic bonding involve?
it involves the transfer of electrons from a metallic element to a non-metallic element.
metals lose electrons forming...
positive ions (cations)
non-metals gain electrons forming...
negative ions (anions)
what is the ionic bond?
the electrostatic force of attraction between the oppositely charged ions which occurs in all directions.
why do ionic compounds have high melting points?
Because the electrostatic force is very strong and so requires a large amount of energy to overcome them.
what are the features of a giant ionic structure?
regular structure
cubic shape
Giant repeating pattern
why are most ionic compounds soluable?
as water molecules are polar they can attract the negative and positive ions and break up the structure.
when do ionic compounds conduct electricity?
when molten or dissolved as the ions are free to move around and carry a charge throughout the structure.
what is covalent bonding?
it is the sharing of outer electrons between two non-metals in order to gain a full outer shell
where is the electrostatic force of attraction in a covalent bond?
between the negative outer electrons and the positive nucleus.
what is a dative or a co-ordinate covalent bond?
where one atom donates 2 electrons to an atom or ion to form a bond
give 2 examples of giant covalent structures
graphite and diamond
describe the bonding in graphite?
each carbon is bonded 3 times with the 4th electron being delocalised.
what is the shape of graphite?
hexagonal shape.
why does graphite have a high melting point?
it has lots of strong covalent bonds
why do graphite layers slide?
they slide as there are weak intermolecular forces between the layers.
can graphite conduct electricity?
Yes, because it has a delocalised electrons between the layers that can carry a charge throughout the structure.
why does graphite have a low density?
the layers are far apart in comparison to covalent bond length.
why is graphite insoluable?
the covalent bonds are too strong to break.
describe the bonding in diamond.
Each carbon is bonded to 4 other carbon atoms.
what is the shape of diamond.
tetrahedral
why is diamond a good conductor of heat?
the tightly packed rigid structure allows heat to conduct well in diamonds.
why does diamond have a high melting point?
it has lots of strong covalent bonds - like graphite which require a lot of energy to be overcome.
does diamond conduct electricity?
no, it has no delocalised electrons
diamond is insoluble - true or false.
true
what is electronegativity?
it is the ability for an atom to attract electrons towards itself in a covalent bond
the most electronegative elements are found..
the further up and right you go.
what is the most electronegative element?
fluorine
what is the pauling scale used for?
it helps us quantify how electronegative an element is.
when can covalent bonds become polar?
when the atoms attached to it have a difference in electronegativity
the bigger the difference in electronegativity the..
more polar the bond will be
what 3 things does electronegativity depend on?
nuclear charge
distance between nucleus and outer electron
sheilding
the smaller the atom..
the closer the nucleus is to the shared electrons, meaning greater electronegativity
the larger the nuclear charge..
the greater the electronegativity
when going up a group what happens to the electronegativity?
it increases due to less shielding by electrons in inner shells.
when going across a period what happens to the electronegativity?
electronegativity increases as the nuclear charge increases.
where are the most electronegative elements found?
at the top right hand corner of the periodic table.
what are the three most electronegative elements?
fluorine, oxygen and nitrogen.
what is polarity?
polarity is about the unequal sharing of the electrons between atoms that are bonded together covalently, it is a property of the bond.
what makes a covalent bond non-polar?
when both atoms are the same e.g F2, both atoms have the same electronegativity there is no unequal distrubution.
what makes a covalent bond polar?
where two atoms of different electronegativity are bonded together.
what is metallic bonding?
metallic bonding consists of a lattice of positively charged metal ions in a sea of delocalised electrons.
what does metallic bonding produce?
A very strong electrostatic force of attraction between positive metal ions and negative electrons.
what does the number of delocalised electrons depend on?
how many electrons have been lost by each metal atom.
are metals good conductors of electricity?
yes, the delocalised electrons that can move throughout the structure and can carry a charge.
why are metals good conductors of heat?
thermal energy is spread quickly due to the closely packed metal ions.
what does the strength of a metal depend on?
the charge on the ion - the greater the charge the greater the number of delocalised electrons and the stronger the electrostatic attraction between the positive ions and the electrons.
the size of the ion, the smaller the ion, the stronger the bond.
why are metals malleable?
since the layers of positive metal ions can slide over each other.
why do metals have high melting and boiling points?
they have giant structures.
why are ionic compounds brittle?
When the layers of alternating charges are distorted, like charges repel, breaking apart the lattice into fragments
what are the three types of intermolecular forces?
van der waals
dipole-dipole
hydrogen bonding
what is the strongest type of intermolecular force?
hydrogen bonding.
what is the weakest intermolecular force?
van der waals.
where do van der waals occur?
they occur between all molecular substances and noble gases, and simple covalent molecules - they do not occur in ionic substances.
what are van der waals also known as?
they are known as induced dipole-dipole interactions.
what occurs in van der waal forces?
the electron cloud of a simple covalent nonpolar molecule moves in either one side of the molecule or the other creating a temporary dipole. this dipole can induce other dipoles on other molecules due to attraction between opposite partial charges.
why are the dipoles produced in van der waal forces temporary?
because electron clouds are constantly moving.
what affects the size of a van der waal force?
the more electrons there are the higher the chance that temporary dipoles will form, this increases the strength of the van der Waal forces.
what can be used to explain the increasing boiling points of the halogens whilst going down the group?
the increasing boiling points of the halogens as you go down the group is due to the increasing number of electrons in the bigger molecules, increasing the strength of the VaW forces.
where do permanent dipole-dipole forces occur?
between polar molecules.
where does hydrogen bonding occur?
hydrogen bonding occurs in compounds with a H attached to one of the 3 most electronegative elements, nitrogen, oxygen and fluorine.
what does the VSPER theory predict?
the valence shell pair electron repulsion theory predicts the shape and bond angles of simple molecules.
what is the order of repulsion?
lone pair – lone pair > lone pair – bond pair > bond pair – bond pair.
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