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Chemistry > Topic 2 - Structure and Bonding > Flashcards

Topic 2 - Structure and Bonding Flashcards

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1
Q

What charge do Group 1 ions always have

A

+1

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2
Q

What charge do Group 2 ions always have

A

+2

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3
Q

What charge do Group 6 ions always have

A

-2

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4
Q

What charge do Group 7 ions always have

A

-1

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5
Q

How do metals form ions

A

They lose electrons from their outer shell making them a positive

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6
Q

How do non-metals form ions

A

They gain electrons to form negative ions

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7
Q

Why are Group 1 and 2 elements more able to form ions

A

-Metals so they can lose electrons to form cations (positive ions)

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8
Q

Why are Group 6 and 7 elements more likely to form ions

A

They are non metals so they gain electrons to form anions

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9
Q

what is Ionic bonding

A

-When a metal and non-metal react together
-The metal atom loses an electron and becomes positively charged
-The non-metal gains an electron and forms a negatively charged ion
-As they are oppositely charged they are attracted to each other by electrostatic forces

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10
Q

What are dot and cross diagrams and how useful are they

A

-They show the arrangement of electrons in an atom/ion. Each electron is represented by a dot or a cross. They show which atom the electrons in an ion originally came from
-Useful for showing how iconic compounds are formed
-Don’t show the structure of the compound, the size of the ions or how they’re arranged

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11
Q

What structure are ionic compounds in

A

-A giant ionic lattice
-Forms a closely packed regular lattice arrangement, held together by strong electrostatic forces of attraction in all directions in the lattice between oppositely charged ions

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12
Q

3D space filling model

A

-Shows relative sizes of the ions and regular pattern of an ionic crystal
-Only let’s you see the outer layer of the compound

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13
Q

Ball and stick model

A

-Shows regular pattern of an ionic crystal and how the ions are arranged
-Suggests the crystal extends beyond what shown in the diagram
-However isn’t to scale so relative sizes not shown and in reality there are no gaps between the ions

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14
Q

Ionic compound properties

A

-High melting and boiling points due to strong bonds between ions which takes lots of energy to overcome
-When solid no electrical charge carried as ions held in place but when melted the ions are free to move so they carry charge
-Some dissolve in water so the ions separate and are free to move so they carry charge

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15
Q

How to work out empirical formula

A

-If dot and cross count up how many atoms there are of each element
-If 3D diagram identify what ions are in the compound and then balance the charges so the overall charge is 0

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16
Q

Covalent bonds

A

-When non-metals atoms bond together they share pairs of electrons to make covalent bonds
-Covalent bonds are very strong as the positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces
-Having a full outer shell gives them the electronic structure of noble gas which is very stable
-Covalent bonding happens in compounds of non-metals and non-metal elements

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17
Q

Model where covalent bonds are single lines

A

-Good for showing how atoms are connected in large molecules
-Don’t show the 3D structure of the molecules or which atoms the electrons in the covalent bond have come from

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18
Q

3D model for covalent bonds

A

-Show the atoms, the bonds and their arrangement in space next to each other
-Can get confusing for large molecules with lots of atoms to include
-Don’t show where the electrons in the bonds have come from

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19
Q

How to find molecular formula of a simple molecular compound

A

-Count up how many atoms of each element there are in a diagram

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20
Q

Properties of simple molecular structures

A

-Atoms within the molecules are held together by very strong covalent bonds
-By contrast the forces of attraction are very weak
-Melting and boiling points low as you only need to overcome weak intermolecular forces to part the molecules from each other
-Most substances are gas or liquids are room temperature
-As molecules get bigger so does strength of intermolecular forces, more energy needed to break so melting and boiling point increase
-Molecular compounds don’t conduct electricity as they aren’t charged so no free electrons or ions

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21
Q

What are Polymers

A

-Long molecules made up of small units linking together that has repeated sections
-Joined by strong covalent bonds

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22
Q

How to draw polymers and find molecular formula

A

-You can draw the shortest repeating section
-Write down the molecular formula of the repeating unit in brackets and put an ‘n’ outside

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23
Q

Polymers properties

A

-Larger intermolecular forces between polymers molecules than simple covalent molecules, so more energy is needed to break them. This means most polymers are solid at room temperature.
-Intermolecular forces are still weaker than ionic or covalent bonds, so they generally have lower boiling points than ionic or giant molecular compound

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24
Q

Giant covalent structures

A

-All the atoms are bonded to each other by strong covalent bonds

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25
Q

Giant covalent structures properties

A

-Very high melting and boiling points as lots of energy is needed to break bonds between
-Don’t conduct electricity as they don’t contain charged particles

26
Q

Diamonds as a giant covalent structure

A

-Only made from carbon atoms
-Each atom forms four covalent bonds this makes diamond really hard
-Those covalent bonds take a lot of energy to break giving diamond a very high melting point
-Doesn’t conduct electricity as has no free electrons

27
Q

Graphite as a giant covalent

A

-Made of only carbon atoms
-Each atom forms three covalent bonds
-Create layers of hexagons
-Each atom has one delocalised electron

28
Q

Graphite properties

A

-No covalent bonds between layers so they’re held together weakly and free to move over each other making graphite soft and slippery, so it’s ideal as lubricating material
-High melting the covalent bonds in the layers take a lot of energy to break
-Only 3 out of carbons 4 atoms outer electrons are used in bonds, so each each carbon atom has one delocalised electron so it can conduct electricity and thermal energy.

29
Q

What are fullerenes

A

Molecules of carbon shaped like closed or hollow balls

30
Q

How are fullrenes arranged

A

-Mainly made up of carbon atoms arranged in hexagons but also can pentagons or heptagons

31
Q

What can fullerenes be used for and why

A

-Can be used to cage other molecules. The structures form around another atom or molecule which is trapped inside. Can be used to deliver a drug into the body
-Fullerenes have a huge surface area, so they could help make great industrial catalysts - individual catalyst molecules could be attached to the fullerenes. They also make great lubricants

32
Q

What are nanotubes

A

-Fullrenes can form these
-Tiny carbon cylinders
-Ratio between the length and diameter of nanotubes is very high

33
Q

Nanotube properties

A

Can conduct electricity and thermal energy
High tensile strength

34
Q

What can nanotubes be used for

A

-Technology that uses very small particles is called nanotechnology
-They can be used in electronics or to strengthen without adding much weight
-such as in tennis racket frames

35
Q

Silicon dioxide (silica) as a giant covalent structure

A

-This is what sand is made
-Each grain of sand is one giant structure of silica

36
Q

What is metallic bonding

A

-Metals also consist of a giant structure
-The electrons in the outer shell of the atom are delocalised there are strong electrostatic forces of attraction between the positive metal ions and the shared negative electrons
-These forces hold the atoms together in a regular structure and are known as metallic bonding which is very strong

37
Q

What substances are held together by metallic bonding

A

Metallic elements and alloys

38
Q

Metallic bonding properties

A

-Electrostatic forces and delocalised sea of electrons are very strong so lots of energy needed to be broken
-Most compounds have very high melting and boiling points so they are generally solid at room temperature
-Delocalised electrons carry electric charge and thermal energy so good conductor of heat and electricity
-Malleable as layers can slide over each other so it can be bent or hammered or rolled into flat sheets

39
Q

Why are alloys harder than pure metals

A

-Different metals mixed together or a metal and another element
-Different elements have different sized atoms so when another element is mixed with a pure metal the new metal atoms will distort the layers of metal atoms so it’s more difficult to slide over each other

40
Q

What is the state matter solids particle theory

A

-Strong forces of attraction hold them close together in fixed positions forming a regular lattic arrangement
-Keep a definite shape and volume and don’t flow like liquids
-Particles vibrate about their particles - the hotter the solid becomes the more they vibrate (so solids expand slightly when heated)

41
Q

What is the state matter liquids particle theory

A

-Weak forces of attraction between the particles so they’re arranged randomly and can move past each other but stick closely together
-Have a definite volume but not shape, and will flow to fill bottom of a container
-Particles are constantly moving with random motion, hotter the liquid faster the faster they move, this causes liquids to expand when heated

42
Q

What is the state matter gas particle theory

A

-Forces of attraction between the particles are very weak so they are free to move and are apart
-Don’t keep definitive shape or volume and will always fill any container
-Move constantly with random motion the hotter the gas gets the fate they move. Either they expand or their pressure increase

43
Q

Negatives of particle theory explaining the three states of matter

A

-The particles aren’t solid or inelastic and they aren’t spheres - they’re atoms, ions or molecules.
-The model doesn’t show the forces between the particles so there’s no way of knowing how strong they are

44
Q

Explain melting in terms of particle theory

A

-When a solid is heated it gains more energy, making the particles vibrate more which weakens the forces that hold the solid together
-At certain temperature (melting point) the particles have enough energy to break free from their positions.

45
Q

Explain boiling in terms of particle theory

A

-When a liquid is heated it gains even more energy, causing the particles move faster weakening or breaking the bonds that hold the liquid together
-At the boiling point the particles have enough energy to break their bonds

46
Q

Explain condensing in terms of particle theory

A

-As a gas cools the particles no longer have enough energy to overcome the forces of attraction so bonds form between them
-At the boiling point so many bonds have formed that the gas becomes a liquid

47
Q

Explain freezing in terms of particle theory

A

-When a liquid cools the particles have less energy so move around less
-There’s not enough energy to overcome the attraction between the particles so more bonds form between the particles
-At the melting point so many bonds have formed between the particles that they’re held in place the liquid becomes a solid

48
Q

What are nano particles

A

Particles with a diameter between 1nm and 100nm, they contain only a few hundred atoms

49
Q

What is the diameter of a coarse particles and what are they called

A

-between 2500nm and 10,000nm
-dust

50
Q

What are fine particles

A

-Particles with a diameter between 100nm and 2500nm

51
Q

What is the area of science that investigates the uses and properties of nanoparticles called

A

nanoscience

52
Q

What is the equation that links volume ratio, surface area and volume

A

surface area to volume ratio = surface area / volume

53
Q

Describe what happens to the surface area to volume ratio as a particle decreases

A

-As they decrease in size their surface area increases in relation to their volume causing the surface area to volume ratio to increase

54
Q

How does the surface area to volume ratio affect nano particles

A

-They have a high surface area to volume ratio (large surface area compared to volume)
-An example of this is you’ll often need less of a material that’s made up of nano particles to work as an effective catalyst compared to a material made up of ‘normal’ sized particles

55
Q

What is nano medicine

A

-There is an idea that the tiny particles can be absorbed by the body more easily
-Meaning they could deliver drugs right into the cells where they’re needed

56
Q

How are nanoparticles that conduct electricity used

A

In tiny electric circuits for computer chips

57
Q

How are silver nano particles used

A

-They have antibacterial properties and can polymer fibres that are then used to make surgical masks and wound dressings and can also be added to deodorants

58
Q

How are nanoparticles being used in cosmetics

A

-They’re being used to improve moisturisers without making them really oily

59
Q

Effects on health by nanoparticles

A

-New products using them have to be tested thoroughly as effects aren’t really understood
-Some are worried we don’t know the long term impacts of them and products using them should be clearly labelled so consumers can choose whether they want to use them or not

60
Q

Nanoparticles in sun cream

A

-Nanoparticles are being used in these as they have been shown to be better than the materials in traditional sun creams at protecting skin from harmful UV rays
-Give better skin coverage than traditional creams
-Not yet clear whether they can get into your body and if they do if they will damage cells
-Also possible when they are washed away they will damage the environment

Chemistry (9 decks)

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