Structure and Bonding Flashcards
What type of structure do ionic compounds make? (PIC BS Ch)
giant ionic lattice
or giant structure
In a giant ionic lattice, what are all of the positive ions surrounded by? (PIC BS Ch)
negative ions
What dimensions do giant ionic lattices have? (PIC BS Ch)
3 dimensional
What are the feactures of a giant ionic lattice? (PIC BS Ch)
- 3 dimensional structure
- alternating positive and negative
- very strong electrostatic forces of attraction or ionic bonds (act in all directions)
What do the strong electrostatic forces of attraction do? (PIC BS Ch)
hold to positive and negative ions in place
What are the key properties of ionic compounds? (PIC BS Ch)
- ionic compounds have very high melting and boiling points
- cannot conduct electricity when they are solid
Why do ionic compounds have very high melting and boiling points? (PIC BS Ch)
the strong electrostatic forces of attraction require a great deal of heat energy to break.
as we heat the ionic solid, the particles vibrate. When the particles vibrate with enough energy, the bonds break and the solid melts. But since they are strong electrostatic forces of attraction, it takes a lot of energy
Why can’t ionic compounds conduct electricity when they are solids? (PIC BS Ch)
the ions are locked in place when a solid by the strong electrostatic forces of attraction. So in a solid the particles can vibrate but they can’t move.
Why can ionic compounds conduct electricity when they are melted or dissolved in water? (PIC BS Ch)
ionic compounds can conduct electricity when they are melted or dissolved in water becuase the ions can now move and carry the electrical charge
Why are solids hard to compress? (SOM SB Ch)
because the particles are packed together in a regular pattern with almost no spaces between the particles and also as they have a fixed shape
Why can’t solids flow from place to place? (SOM SB Ch)
because in a solif the particles can vibrate but they cannot move from place to place
why are liquids hard to compress? (SOM SB Ch)
becuase the particles are colse together with not many spaces between them.
Why can liquids fill the containor and flow from place to place? (SOM SB Ch)
the particles in a liquid can move
Why are gases easy to compress? (SOM SB Ch)
the particles are widely spaced
why can gases spread out and fill the space of their container? (SOM SB Ch)
the particles in a gas move quickly and randomly
Why do we need to apply energy into a solid to get a liquid? (SOM SB Ch)
liquids move more than solids meaning they have higher kinetic energy. The energy is needed to break the forces of attraction between the particles in a solid. Once they are broken the particles can now move around.
wha is it called when we convert a gas back into a liquid? (SOM SB Ch)
condensing / condensation
what are the limitations of a simple particle model showing the states of matter? (SOM SB Ch)
- the SPM assumes that all particles are solid spheres which is not the case. They should have lots of different shapes and they are not solid.
- The SPM assumes that there are no forces between the particles which isnt correct as there are forces of attraction between the particles
what kind of melting and boiling points do small covalent molecules have? (POSCM BS Ch)
low ones so they are usually gases or liquids at room temperature.
why do small covalent molecules have low melting and boiling points? (POSCM BS Ch)
- the atoms in each molecule are held together by strong covalent bonds
- there are very weak intermolecular forces between one molecule and another
as we increase the temperature the vibrations also increase. At a certain point the vibration is strong enough to break the weak intermolecular forces holding the molecules to each other. At this point the molecules boil. So because the intermolecular forces are weak, it does not require much energy to break them
why is it that the increase in size of molecules brings the increase of boiling points? (POSCM BS Ch)
because the intermoleculurar forces increase and require more energy to break
do small covalent molecules conduct electricity? (POSCM BS Ch)
because they do have an overall electric charge
What are the three giant covalent structures? (DASD BS Ch)
diamond
silicon dioxide (or silica)
graphite
What states are giant covalent structures at room temperature and why? (DASD BS Ch)
always solids because they all have high melting and boiling points
Why do giant covalent structures have high melting and boiling points? (DASD BS Ch)
because they have millions of strong covalent bonds and in order to melt or boil these substances, we have to break all of these covalent bonds. which takes a great deal of energy.
What is diamond formed by? (DASD BS Ch)
the element carbon
Why can carbon atoms only form 4 covalent bonds? (DASD BS Ch)
because they only have four electrons to share.
What makes diamond and extremely hard substance? (DASD BS Ch)
there are millions and millions of carbon atoms covalently bonded together.
Can diamond conduct electricity? (DASD BS Ch)
NO because all of the outer electrons are in covalent bonds which means that diamond has no free electrons to carry electrical charge
What does silicon dioxide contain? (DASD BS Ch)
both of the elements silicon and oxygen covalently bonded togehter
Why does silicon dioxide have a high melting and boiling point? (DASD BS Ch)
it has a large amount of covalent bonds and it requires a lot off energy to break these.
What are the key properties of graphite? (G BS Ch)
~ it is soft and slippery
~ very high melting and boiling point
~ a good conductor of both electricity and of heat
What is the structure of graphite? (G BS Ch)
Each carbon atom covalently bonds to three of carbond atoms.
The carbon atoms form hexagonal rings, rings of six carbon atoms
The hexagonal rings are arranged into layers and there are no covalent bonds between the layers. Which means that they can slid over eachother which meakes graphite soft and slippery
What is graphite often used for? (G BS Ch)
lubrication in machines because it reduces the friction between moving parts as it is soft and slippery.
Why is graphite a good conductor of heat and electricty? (G BS Ch)
Each carbon atom covalently bonds with three other carbon atoms which leaves one electron spare and these electrons are released from the carbon atoms ~ delocalised electrons. These can move which means that they can conduct electricity and thermal energy. This makes it similar to metals
Why is graphite similar to metals? (G BS Ch)
just like graphite, metals also have delocalised electrons that can move and they are good conductors of electricity and heat.
What is graphene? (GF BS Ch)
a single layer of graphite meaning that it is only one atom thick
What are the properties of graphene? (GF BS Ch)
~ it is a good conductor of electricity because it has delocalised electrons which can move through the graphene molecules carrying electrical charge. so could be used in electronics
~ it is stong
~ high melting and boiling point
the last two are becuase it has a large number of strong convalent bonds which require lots of energy to break.
What can fullerenes be used for? (GF BS Ch)
- used to deliver drugs such as pharmaceuticals into the body
- used as libricants in machines where they reduce friction between moving parts
- cataysts to speed up reactions
What are carbon nanotubes? (GF BS Ch)
fullerenes shaped into long cylinders with a relatively small diameter (high length to diameter ratio)
they have rings formed from 6 carbon atoms
What are the usefull properties of carbon nanotubes? (GF BS Ch)
~ high tensile strength so we can apply a grat deal of stretching force to a carbon nanotube before it breaks
~ they have delocalised electrons which makes them good conductors of electricity and heat
What is one use of carbon nanotubes? (GF BS Ch)
~ reinforce materials like tennis rackets
