bonding, structure and properties of matter 2 Flashcards
what are ions
are charged particles trying to lose or gain electrons to achieve a full outer shell
what happens when metals form ions
they lose electrons to from positive ions
what happens when non metals form ions
they gain electrons to from negative ions
how many electrons do group two lose ( ions )
2 electrons
how many electrons do group one lose ( ions )
1 electron
how many electrons do group 6 gain ( ions )
2 electrons
how many electrons do group 7 gain ( ions )
1 electron
what is ionic bonding
when a metal and non metal react together the metal atom loses electrons to form a positively charged ion and the non metal gains these electrons to form a negatively charged ion. the oppositely charged ions are strongly attracted to one an another by electrostatic forces
properties of an ionic compound
1) high melting and boiling point due to many strong bonds
2) when solid the ions are held in place so they don’t conduct electricity
3) when the ionic compound melts the ions are free to move and can conduct electricity
4) when compound dissolves in water the ions separate and are free to move in the solution
what is covalent bonding
when non metal atoms bond together they share pairs of electrons to make covalent bonds.
the positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces, making covalent bonds very strong.
properties of covalent bonding
1) very strong covalent bonds, by contrast the forces between these molecules are weak
2) only need to break inter molecule forces so the melting and boiling point is low
3) as they get bigger the intermolecule forces increases so more energy is needed increasing the melting and boiling point
what is metallic bonding
electrons in the outer shell of the metal atoms are delocalised. There are strong forces of electrostatic attraction between the positive metal ions and the shared negative electrons
metallic bonding is very strong
why are metals solid at room temp
electrostatic forces between the metal atoms and the delocalised sea of electrons are very strong so need lots of energy to be broken
This means that most compounds with metallic bonds have very high meting and boiling points.
what makes metals good conductors of electricity and heat
delocalised electrons carry electrical current and thermal energy through the whole structure
Why are metals malleable
atoms can slide over each other making malleable
what is wrong with pure metals and what is done to improve it
they are soft so need to be mixed with other metals so they are harder
Why are alloys strong
different sized atoms so will distort the layers of metal atoms making it difficult for them to slide over each over
what is the diameter of a coarse particle
2500 nm and 10000 nm
what is the diameter of a fine particle
100 nm and 2500 nm
what is the diameter of a nano particle
1 nm and 100 nm
surface area to volume ratio =
surface area / volume
What happens as particles decrease in size
surface area increases in relation to volume
uses of nano particles
1) used for catalysts because of there surface to volume ratio
2) tiny particles are absorbed more easily so are good for delivering drugs
3) they conduct electricity
4) silver nano particles have antibacterial properties making them good for medical equipment
5) used in cosmetics
effects of nano particles on health
important that they are tested
some people worrie that the products have not been tested
people wont them to be labelled clearly
they can get in your body and effect the environment when washed off
how are atoms joined in a polymer
strong covalent bonds
why are most polymers solid at room temp
inter molecular forces between polymer molecules are larger than between simple covalent molecules so more energy is needed to break them
properties of giant covalent structures
very high melting and boiling points as lots of energy is needed to break the covalent bonds
don’t conduct electricity because they don’t have charged particles.
what are allotropes
different structural forms of the same element in the same physical state
why is diamond hard
giant covalent structure made up of carbon atoms that each contain four covalent bonds
other properties of diamond
take a lot of energy to break bonds so has a high melting and boiling point
dont conduct electricity because it has no free electrons
what is the structure of Graphite
each carbon atom only forms three covalent bonds creating sheets of carbon atoms arranged in hexagons
what makes graphite so soft and slippery
aren’t any covalent bonds between the layers, so are free to move over each over.
Other properties of graphite
high boiling point because of covalent bonds
conducts electricity and thermal energy because there are delocalised electrons
what is the structure of graphene
a sheet of carbon atoms joined together in hexagons
the sheet is one atom thick
properties of graphene
light so can be added to composite materials to improve there strength without adding weight
conduct electricity because of its delocalised electron
structure of fullerenes
are molecules of carbon shaped like closed tubes or hollow balls
mainly made up of carbon atoms arranged in hexagons, but can also contain pentagons
why are fullerenes good catalysts
huge surface area
how are fullerenes used to deliver drugs
used to cage other molecules by trapping them inside
what are nano tubes
tiny carbon cylinders
properties of nano tubes
conduct electricity
high tensile strength (don’t break when they are stretched)
ratio between length and diameter of nano tubes is high
what can form nano tubes
fullerenes
