bonding - topic 2

Question 1

what are the limitations of the simple particle model?

Answer 1

-it assumes all particles are solid spheres which is false as particles have lots of different shapes and are not solid
-assumes there are no forces between particles which is false
as forces of attraction between the particles have an impact on the melting and boiling points of a substance

Question 2

when does ionic bonding take place?

Answer 2

-when a metal and a non-metal react

Question 3

key facts of ionic bionding

Answer 3

-elements react in order to achieve a full outer energy level
-by doing this, they achieve the stable electronic structure of a noble gas ( a full outer energy shell)

Question 4

what happens in ionic bonding? - group 1 + 7

Answer 4

-group 1 metals lose one electron forming a one positive ion
-group 7 non-metals gain one electron forming a one negative ion
-both ions now have a full outer energy level

Question 5

what happens in ionic bonding ? group 2 + 6

Answer 5

-group 2 metals lose 2 electrons forming a 2+ ion
-group 6 non-metals gain 2 electrons forming a 2- ion
-both ions now have a full outer energy level

Question 6

describe the structure of giant ionic lattice

Answer 6

-ionic compounds form giant structures called giant ionic lattices
-in a giant ionic lattice, every positive ion is surrounded by negative ions and every negative ion is surrounded by positive ions
-three dimensional structure
-strong forces of attraction between the positive and negative ions which are called electrostatic forces of attraction
-ionic bonds act in all directions

Question 7

what are electrostatic forces?

Answer 7

-strong forces of attraction between the positive and negative ions

Question 8

what are two key properties of ionic compounds?

Answer 8

-ionic compounds have very high melting and boiling points
-this is because the strong electrostatic forces of attraction require a large amount of heat energy to break
-they cannot conduct electricity when they are solids

Question 9

why can ionic compounds not conduct electricity when they are solid?

Answer 9

-ions are locked in place by the strong electrostatic forces of attraction
-in a solid, the ions can vibrate but they cannot move

Question 10

why can ionic compounds conduct electricity when they are melted or dissolved in water?

Answer 10

-the ions can now move and carry electrical charge

Question 11

what is covalent bonding?

Answer 11

-when non-metal atoms bond together.

Question 12

what is a key property of small covalent molecules?

Answer 12

-low melting and boiling points
-> usually gases because they boil at below room temperature ( x water )

Question 13

why do small covalent molecules have low melting and boiling points?

Answer 13

-there are weak intermolecular forces which do not require a lot of energy to break

Question 14

3 key points about small covalent molecules?

Answer 14

-atoms in each molecule are held together by strong covalent bonds
-weak intermolecular forces which do not require a large amount of energy to break
-do not conduct electricity because they do not have an overall electric charge

Question 15

how does a small covalent molecule become a gas?

Answer 15

-as we increase the temperature, the vibration of the molecules increases
-at a certain point, this vibration is strong enough to break the weak intermolecular forces holding the molecules to each other which do not require much energy

Question 16

what is a difference between small and giant covalent substances?

Answer 16

-small covalent substances have a small number of covalent bonds while large covalent substances contain millions of covalent bonds

Question 17

2 key facts about giant covalent substances?

Answer 17

-always solids at room temperature because they have high melting and boiling points
-giant covalent substances contain millions of covalent bonds so melting and boiling these substances require a large amount of energy

Question 18

describe the properties of diamond

Answer 18

-formed from the element carbon
-four strong covalent bonds for each carbon atom
-very hard
-high melting and boiling points
-diamonds can not conduct electricity

Question 19

why can diamonds not conduct electricity?

Answer 19

-all of the outer electrons are in covalent bonds so diamond has no free electrons to carry electrical charge

Question 20

why do diamonds have high melting and boiling points?

Answer 20

-they have strong covalent bonds which require large amounts of energy in order to break

Question 21

describe the 2 properties of silicon dioxide ( silica)

Answer 21

-contains the elements silicon and oxygen covalently bonded together
-high melting and boiling points

Question 22

why does silicon dioxide have a high melting and boiling point?

Answer 22

-it has a huge number of strong covalent bonds which require a great deal of energy in order to break

Question 23

what are the 4 key properties of graphite?

Answer 23

-soft and slippery
-high melting and boiling point
-good conductor of both electricity and of heat
-three covalent bonds for each carbon atom

Question 24

why is graphite soft and slippery?

Answer 24

-hexagonal rings of carbon atoms are arranged into layers
-there are no covalent bonds between layers allowing them to slide over each other
-can be used as a lubricant

Question 25

why does graphite have a high melting and boiling point?

Answer 25

-it contains a large number of strong covalent bonds which require a large amount of energy to break

Question 26

why is graphite a good conductor of both electricity and heat

Answer 26

-they have delocalised electrons that are free to move and carry electrical charge

Question 27

why are metals good conductors of electricity ?

Answer 27

-metals have delocalised electrons that can move and carry electrical charge

Question 28

what is graphene?

Answer 28

- a single layer of graphite that is one atom thick

Question 29

what are the 3 properties of graphene?

Answer 29

-good conductors of electricity -extremely strong -has a high melting and boiling point

Question 30

why will graphene be useful in electronics?

Answer 30

-they are good conductors of electricity as they have delocalised electrons which can move through the graphene molecules and carry electrical charge

Question 31

why is graphene useful for producing new materials?

Answer 31

-extremely strong -high melting and boiling because it has many strong covalent bonds which require a great deal of energy to break

Question 32

describe the properties of fullerenes?

Answer 32

-hollow shapes -hexagonal rings of 5 or 7 carbon atoms

Question 33

describe the properties of the buckminsterfullerene?

Answer 33

-it contains sixty carbon atoms arranged in a hollow sphere -carbon atoms form rings with either six carbon atoms or with five carbon atoms

Question 34

what are the 3 uses of fullerenes?

Answer 34

-deliver drugs such as pharmaceuticals into the body -lubricants in machines where they reduce friction between moving parts -catalysts to speed up chemical reactions

Question 35

what is an example of a group of fullerenes?

Answer 35

-carbon nanotubes

Question 36

what are the 5 properties of carbon nanotubes?

Answer 36

-shaped into long cylinders with a relatively small diameter -very high length to diameter ratio -delocalised electrons -high tensile strength -reinforce materials

Question 37

why are most polymers solids at room temperature?

Answer 37

-polymers have strong intermolecular forces of attraction which require a large amount of energy to break -polymers have high melting points

Question 38

bonding in metals + structure

Answer 38

-a giant structure of atoms arranged in regular layers -strong electrostatic force of attraction between the sea of delocalised negative electrons and the positive metal ions -this is called metallic bonding

Question 39

why do metals have high melting and boiling points

Answer 39

-metallic bonds are strong and require a great deal of energy in order to break

Question 40

why are metals good conductors of heat ?

Answer 40

-the delocalised electrons can move and carry thermal energy which allow metals to conduct heat

Question 41

why can metals be bent or shaped?

Answer 41

-the layers of atoms can slide over each other this is a problem because some pure metals are not hard enough to be useful including copper, gold, and iron so we make alloys.

Question 42

what is an alloy ?

Answer 42

-a mixture of metals

Question 43

why are alloys harder than pure metals?

Answer 43

-the different sizes of atoms distorts the layers -making it more difficult for the layers to slide over each other

Question 44

what is the diameter of coarse particles (PM10 or dust) ?

Answer 44

-diameter between 1x10^-5m and 2.5x10^-6 m

Question 45

what is the diameter of fine particles?

Answer 45

-diameter between 100-2500 nanometres (1x10^-7 and 2.5 x 10^-6)

Question 46

what is the diameter of of nanoparticles?

Answer 46

-diameter between 1-100 nanometres

Question 47

1 key fact about particles

Answer 47

-as the particle size decreases by ten times, the surface area to volume ratio increases by ten times

Question 48

why are nanoparticles useful?

Answer 48

-huge surface area to volume ratio

Question 49

what are 4 uses of nanoparticles?

Answer 49

-catalysts -medicines -cosmetics -deodorants

Question 50

what are the risks involved in using nanoparticles?

Answer 50

-when used in sun screams, cosmetics and deodorants it is possible nanoparticles can be absorbed into the body and enter our cells --potential long-term effects are unknown

Question 51

what is an advantage of the dot and cross diagram

Answer 51

-we use dots to represent the electrons from one atom and use crosses to represent the electrons from another atom so it is clear where the electrons are coming from

Question 52

what is a disadvantage of the stick and dot diagram?

Answer 52

-they don't tell us about the shape of the molecule

Question 53

what are three disadvantages of the 2 dimensional stick diagram ?

Answer 53

- covalent bond is shown as a stick so we cannot tell which electron in the covalent bond came from which atom -they give us no idea of outer electrons that are not in bonds -do not give accurate information on the shape of the molecule

Question 54

what is the benefit of a 3 dimensional stick diagram?

Answer 54

-it gives us the shape of the molecule

Question 55

what is the benefit of a ball and stick diagram? + negative (2)

Answer 55

-it allows us to clearly see the ions in 3 dimensions but the ions are widely spaced when in reality, the ions are packed together + only shows a tiny part of the giant crystal lattice

Question 56

what is a benefit and negative of space filling diagram?

Answer 56

-gives a better idea of how closely packed the ions are -it can be difficult to see the three dimensional packing + only shows a tiny part of the giant crystal lattice.