bonding Flashcards
what is ionic bonding?
non metal + metal
what holds ionic bonds together?
electrostatic forces of attraction between oppositely charged ions (positive metal cations and negative non-metal anions)
what is an ion?
positively charged (missing electrons) or negatively charged (has extra electrons) atoms/groups of atoms
how do ionic compounds bond?
electrons trasfered so both ions have full outer shells
properties of ionic compounds (4)
- very high melting and boiling points
- hard but brittle
- soluable in water
- conduct electricity as liquids (ie disolved) but not as solids
why do ionic compounds have very high melting and boiling points ?
strong electrostatic forces of attraction between oppositely charged ions throughout the giant structure require lots of energy to overcome
why are ionic compounds hard but brittle?
when layers slide, ions with the same charge repel each other, breaking up the giant lattice structure
what structure are ionic compounds?
giant lattice, meaning one ion of x is completly surrouded by oppositely charged ions of y
why are ionic compounds soluable in water?
water is a polar molecule so the oppositely charged ions are attracted and therefore split up by the water, breaking up the lattice
why are ionic compounds not able to conduct electricity as solids?
ions are held in a fixed position so not able to carry a charge (conduct electricity)
why are ionic compounds able to conduct electricity when molten/disolved ?
ions are free to move so can carry a charge
why does MgO have a higher melting point than NaCl?
MgO has a double charge meaning 2 electrons are transferred (Mg2+, O2-) so the electrostatic force of attractio is much stronger than the single bond in NaCl (Na+, Cl-)
what does -ide mean?
negative ion eg chloride is Cl-
what does -ate mean?
negative ion, oxygen also present
eg SO4 2- is sulfate and oxygen
what are covalent bonds?
non metal + non metal (both need to gain electrons so share one or more pairs)
electrostatic attraction betwee the positvely charged protons in the nucleus and the negative shared pair of electrons
what is the structure of simple covalent substances?
strog covalent bonds between atoms in a molecule BUT weak intermolecular forces between neighbouring molecules
size of molecules
very small (only slightly larger than atoms), 10^-10 m
why do simple covalent compounds have low melting and boiling points?
weak intermolecular forces betwee molecules do not need lots of energy to overcome
why are simple covalent compounds not able to conduct electricity?
no ions or electrons free to move
why are simple covalent molecules insoluable?
water is polar but molecules are not charged so it is in not able to split them i
what is the structure in metallic bonding?
positive metal cations held together by a sea of delocalized electrons in layers due to a strong electrostatic force of attraction
properties of metals (4)
- ductile ad malleable
- high melting and boiling points
- good conductors of electricity
- good conductors of heat
properties of simple covalent molecules (3)
- very low melting and boiling points
- don’t conduct electricity
- insoluable
why are metals ductile and malleable?
layers are able to move across each other since movement of sea of delocalized electrons holds whole structure together
why do metals have high melting and boiling points?
lots of strong electrostatic attraction in a giant metallic lattice so lots of energy needed to overcome
why are metals good conducturs of electricity?
delocalized electrons can move and carry a charge
why are metals good conducturs of heat?
- delocalized sea of electrons can move
- when heated, move more due to increase in kinnetic energy so transfer the energy (and heat) to other electrons
key words - ionic bonding
- strong electrostatic forces of attraction between oppositely charged ions
- giant lattice
- transfer of electrons
key words - metallic bonding
- delocalized sea of electrons
- layers
- giant lattice structure
- positive metal cations
key words - simple covalent bonding
- strong covalent bonds between atoms
- weak intermolecular bonds between molecules
what is the structure of giant covalent substances?
giant lattice
what is the difference between simple and giant covalent substances?
in simple covalent substaces there are weak intermolecular bonds between molecules whilst in giant covalent there are no weak intermolecular bonds, only strong covalent bonds between atoms
what are diamonds and graphite examples of?
- giant covalet substances
- both forms of carbon
why are diamond and graphite different?
diamond - one carbon bonded to 4 others in a tetrahedral structure
graphite - one carbon bonded to 3 others in layers
what are the melting points of diamonds and graphite and why?
- very high because there are lots of strong covalent bonds throughout the giant structure to be overcome
why are diamonds hard?
strong covalent bonds throughout giant structure require lots of energy to overcome
why is graphite soft?
soft due to weak intermolecular forces between the layers , meaning layers can slide easily
conductability of diamond and why
- cannot conduct electricity
- no delocalized electrons since all electrons are being shared in covalet bonds/ fixed structure
conductability of graphite and why
very good conductor due to delocalized electrons between layers (which can break free from the weak intermolecular forces) which can move freely
uses of diamonds and why
- industrial drill bits (hardness)
- jewlery shine
uses of graphite and why
- pencil lead and industrial lubricators > layers can easily slide + soft
- electrodes > good electrical conductivity
what are fullerenes and how can they be used?
- SIMPLE covalent substances
- hollow molcules of carbon shaped like tubes or balls (eg C60 - buckministerfullerene) aranged into hexagons/pentagons/heptagon rings
- can be used as carbon nanotubes (often base for catalysts due to large surface area)
what is graphene amd how can it be used?
- single sheet of carbon atoms bonded together in hexagons
- one atom thick so can strengthen composite materials without adding to weight
what are polymers and their uses ?
- long chain-like molecules covalently bonded
- strong covalent bonds (all are solid at room temp) but weak intermolecular forces
- eg polyethene which has very weak intermolecular forces making it flexibke and ideal for plastic bags
identifying type of substance
what type of substance is it if it has high bpt ad mpt?
not simple molecular
(giant, ionic or metal)
identifying type of substance
what type of substance is it if it has low mpt ad bpt, bad conductor in all states?
simple covalent
identifying type of substance
what type of substance is it if it can conduct when solid?
metal
identifying type of substance
what type of substance is it if it has high mpt and bpt, poor conductivity (1 exception) ?
giant covalent
apart from graphite which is a good conductor of electricity
identifying type of substance
what type of substance is it if it has high mpt and bpt, can conduct as a liquid/aqueous but not as a solid?
ionic
