bonding, structure and properties of matter

Question 1

ions

Answer 1

atom with a positive or negative charge
atom that has lost/gained an electron
- can be single atoms or groups of atoms

when atoms lose/gain electrons to form ions, they are trying to get a full outer shell
- atoms with a full outer shell are very stable

the number of electrons lost/gained is the same as the charge on the ion

Question 2

metals form ions

Answer 2

lose electrons from their outer shell to form positive ions (cations)

Question 3

non-metals form ions

Answer 3

gain electrons in their outer shell to form negative ions (anions)

Question 4

groups lost likely to form ions

Answer 4

1 & 2, 6 & 7

Question 5

elements in the same group have the same number of

Answer 5

outer electrons

Question 6

elements in the same period have the same number of

Answer 6

electron shells

Question 7

ionic bonding

Answer 7

transfer of metals
metal and non-metal
electrostatic attraction between oppositely charged ions

when metal + non-metal react, the metal atom loses electrons to form a positively charged ion and the non-metal gains these electrons to form a negatively charged ion
- these oppositely charged ions are strongly attracted to one another by electrostatic forces (an ionic bond)

Question 8

dot and cross diagrams

ionic bonding

draw one

Answer 8

show how ionic compounds are formed
show the arrangement of electrons in an atom or ion
- each electron is represented by a dot or cross
- diagrams can show which atom the electrons in an ion originally came from
pros
- show how ionic compounds are formed
cons
- don’t show the structure of the compound
- don’t show the size of the ions or how they’re arranged

Question 9

ionic compounds

Answer 9

a giant structure of ions - giant ionic lattice
- held together by electrostatic forces of attraction between oppositely charged ions
- ions form a closely packed regular lattice arrangement
- strong ionic bonds require lots of energy to break
- there are very strong electrostatic forces of attraction between oppositely charged ions in all directions in the lattice
- the structure is regular and repeating (a ‘lattice’)
- crystal structure

e.g. sodium chloride (table salt)

Question 10

ionic compound properties

Answer 10

• high melting + boiling points - many strong bonds between ions lots of energy required
• solids at room temp
• regular crystal structures
• lots of energy required to break the strong forces of electrostatic attraction that make the ionic bonds between oppositely charged ions
• don’t conduct electricity when solid - the ions are held in place
• -conduct electricity when liquid - the ions are free to move + will carry electric charge
• some ionic compounds also dissolve in water - the ions separate and are all free to move in the solution, so will carry electric charge

Question 11

ball and stick model

Answer 11

shows the regular pattern of a giant ionic lattice (ionic crystal)
pros
shows how all the ions are made
suggests that the crystal extends beyond what’s shown in the diagram
cons
model isn’t to scale (relative sizes of the ions aren’t shown)
in reality there aren’t any gaps between ions

Question 12

covalent bonds

Answer 12

the sharing of electrons between 2 non-metal atoms
- the positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces, making covalent bonds very strong

• atoms only share electrons in their outer shells (highest energy levels)
• each single covalent bond provides one extra shared electron for each atom
• each atom involved generally makes enough covalent bonds to fill its outer shell - the electronic structure of a noble gas (very stable)
• covalent bonding happens in compounds of non-metals and in non-metal elements

Question 13

dot and cross diagram

covalent bonds

draw one

Answer 13

electrons drawn in the overlap between the outer orbitals of two atoms are shared between those atoms
pros
show which atoms the electrons in a covalent bond come from
cons
don’t show the relative sizes of the atoms
don’t show how the atoms are arranged in space

Question 14

displayed formula diagram

covalent bonds

draw one

Answer 14

shows the covalent bonds as single lines between atoms
pros
show how atoms are connected in large atoms
cons
don’t show the 3D structure of the molecule, or which atoms the electrons in the covalent bond have come from

Question 15

3D model diagram

covalent bond

draw one

Answer 15

pros
show the atoms, the covalent bonds and their arrangement in space next to each other
cons
3D models can get confusing for large molecules where there are lots of atoms to include
- don’t show where the electrons in the bonds have come from

Question 16

ammonia

Answer 16

NH₃

Question 17

simple molecular covalent structures

Answer 17

made up of molecules containing a few atoms joined together by covalent bonds
examples:
H₂ - hydrogen
Cl₂ - chlorine
O₂ - oxygen
N₂ - nitrogen
H₂O - water

Question 18

simple molecular substances properties

Answer 18

• atoms within the molecules are held together by very strong covalent bonds
• by contrast, the forces of attraction between these molecules are very weak
• low melting and boiling points - small intermolecular forces to break and you don’t have to break the covalent bonds - molecules are easily parted from one another
• most are liquids/gases at room temp
• as molecules get bigger, the strength of the intermolecular forces increase, so more energy is needed to break them - melting + boiling points increase
• don’t conduct electricity as they aren’t charged so no free electrons or ions

Question 19

polymers

Answer 19

large long chain molecules made up of lots of small monomers joined together by covalent bonds
long chains of repeating units
atoms joined by strong covalent bonds
- intermolecular forces are larger than between simple covalent molecules, however weaker than ionic or covalent bonds (lower boiling points than ionic or giant molecular compounds)
- most are solid at room temp

Question 20

giant covalent structures

+ examples

Answer 20

macromolecules
- all the atoms are bonded to each other by strong covalent bonds
- very high melting + boiling points as lots of energy is required to break the covalent bonds between the atoms
- don’t conduct electricity - don’t contain charged particles - not even when molten (excluding graphite)
examples:
Diamond - made from carbon atoms only - each carbon atom forms four covalent bonds in a very rigid giant covalent structure
Graphite - made from carbon atoms only - each carbon atom forms three covalent bonds to create layers of hexagons. each carbon atom also has one delocalised electron
Silicon dioxide - sometimes called silica, what sand is made of. each grain of sand is one giant structure of silicon and oxygen

Question 21

allotropes of carbon

Answer 21

diamond
graphite
graphene
fullerenes

Question 22

diamond

Answer 22

has a giant covalent structure made up of carbon atoms that each form four covalent bonds - makes diamond very hard
- strong covalent bonds take a lot of energy to break and give diamond a very high melting point
- doesn’t conduct electricity because it has no delocalised electrons

Question 23

graphite

Answer 23

contains sheets of electrons
- each carbon atom only forms three covalent bonds, creating sheets of carbon atoms arranged in hexagons
- aren’t any covalent bonds between the layers - they’re only held together weakly, so they’re free to move over each other - makes graphite soft and slippery, so it’s an ideal lubricating material
- high melting point - the covalent bonds in the layers need loads of energy to break
- only three out of each carbon’s four outer electrons are used in bonds, so each carbon atom has one electron that’s delocalised (free) and can move
- therefore graphite** conducts** electricity and thermal energy

Question 24

graphene

Answer 24

one layer of graphite
- a sheet of carbon atoms joined together in hexagons
- the sheet is one atom thick, making it a two-dimensional substance - thin
- the network of covalent bonds makes it very strong
- incredibly light, so can be added to composite materials to improve their strength without adding much weight
- contains delocalised electrons so can conduct electricity through the whole structure - has the potential to be used in electronics

Question 25

fullerenes

Answer 25

from spheres and tubes - molecules of carbon, shaped like closed tubes or hollow balls - mainly made up of carbon atoms arranged in hexagons, but can also contain pentagons or heptagons *uses:* - **medicine** - drug delivery into the body - 'cage' other molecules - fullerenes have a huge surface area, so could help make great industrial **catalysts** - individual catalyst molecules could be attached to the fullerenes - make great **lubricants** e.g. buckminsterfullerene - C₆₀ - forms a hollow sphere

Question 26

carbon nanotubes

Answer 26

tiny carbon cylinders -high tensile strength (don't break when stretched) -conduct both electricity and thermal energy (delocalised electrons) *uses:* - **electronics** - strengthen carbon fibre **tennis rackets** (strengthen materials without adding much weight) - **lubricants**

Question 27

metallic bonding

Answer 27

metal + metal - very strong - the electrons in the outer shell of the metal atoms are delocalised - strong forces of **electrostatic attraction** between the positive metals ions and the shared negative electrons - the forces of attraction hold the atoms together in a regular structure - delocalised electrons are free to move throughout the structure + are shared throughout the structure so the metallic bonds are strong substances held together by metallic bonding include metallic elements and alloys - the *delocalised electrons* produce all the properties of metals

Question 28

properties of metals

Answer 28

*most are solid at room temp* - the electrostatic forces between the metal atoms and the delocalised electrons are very story so need lots of energy to be broken - most compounds with metallic bonds have high melting + boiling points *good conductors* - contain many delocalised electrons which carry charge and thermal energy through the whole structure, so metals are good conductors *most are malleable* - the layers of atoms in metals can slide over each other - means they can be bent/hammered/rolled into flat sheets

Question 29

alloys + pure metals

Answer 29

a mixture of two or more metals or a metal and another element - harder so more useful than pure metals - 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, making it more difficult for them to slide over each other - makes alloys harder than pure metals pure metals (consist of a single element) are often too soft when they're pure so mixed with other metals to make them harder

Question 30

states of matter

Answer 30

solid, liquid, gas which state something is in at a certain temperature depends on how strong the forces of attraction are between the particles of the material - how strong the forces are depends on: - **the material** (structure of substance + type of bonding) - the **temperature** - the **pressure**

Question 31

particle theory

Answer 31

a model that explains how the particles in a material behave in each of the three states of matter by considering each particle as a small, solid, inelastic sphere - isn't perfect as in reality particles aren't solid or inelastic and aren't spheres - they're atoms, ions or molecules - model doesn't show the forces between the particles, so no way of knowing how strong they are

Question 32

solids

Answer 32

- **strong** forces of attraction between particles, which holds them close together in fixed positions to form a very regular lattice arrangement - particles **don't move** from their positions, so all solids keep a definite shape and volume, and don't flow like liquids - particles **vibrate** about their positions - the *hotter* a solid becomes, the *more* they vibrate (causing solids to expand slightly when heated)

Question 33

liquids

Answer 33

- **weak** force of attraction between particles - randomly arranged and free to move past each other, but tend to stick closely together - liquids have a definite volume but **don't** keep a definite shape and will *flow* to the bottom of a container - particles are **constantly** moving with **random** motion. The **hotter** the liquid gets, the **faster** they move - causes liquids to *expand* slightly when heated

Question 34

gases

Answer 34

- **very weak** forces of attraction between particles - they're free to move and *far apart* - travel in straight lines - **don't** keep a definitive *shape* or *volume* and will always **fill** any container - particles move **constantly** with **random motion** - the *hotter* the gas gets, the *faster* they move - gases either **expand** when heated, or their **pressure increases**

Question 35

state symbols

Answer 35

tell you the state of a substance in an equation (s) - solid (l) - liquid (g) - gas (aq) - aqueous (dissolved in water)

Question 36

melting | changing state

Answer 36

- solid **heated**, particles gain more energy - particles **vibrate** more, *weakens *the forces holding the solid together - at melting point the particles have enough energy to *break* free from their positions (melting) and the solid turns into a liquid

Question 37

boiling | changing state

Answer 37

- liquid **heated**, particles gain more **energy** - particles move **faster**, *weakens* and *breaks* bonds holding liquid together - boiling point - particles have enough energy to break their bonds (boiling/evaporating) - liquid becomes a gas

Question 38

condensing | changing state

Answer 38

- gas **cools**, particles no longer have enough *energy* to overcome the forces of attraction between them - bonds *form* between the particles - at the *boiling point*, so many bonds have formed between the gas particles that the gas becomes a **liquid** (condensing)

Question 39

freezing | changing state

Answer 39

- when a liquid **cools**, the particles have *less* energy, so move around less - not enough energy to overcome the attraction between particles, so **bonds** form between them - at melting point, so many *bonds* have formed between particles that they're held in place - liquid becomes a *solid* (freezing)

Question 40

amount of energy required for a substance to change state depends on...

Answer 40

how strong the forces between particles are - the **stronger** the forces, the **more energy** is needed to break them, and so the *higher* the melting and boiling points of the substance

Question 41

nanoparticles

Answer 41

very small particles - contain only a few hundred atoms compared to 'normal' billions of atoms diameters between 1nm-100nm in size - have a very high surface are to volume ratio - surface area is very large compared to volume - can exhibit different properties different to those for the same material in bulk e.g. you often need less of a material that's made up of nanoparticles to work as an effective catalyst compared to a material made up of 'normal' sized particles

Question 42

surface area to volume ratio

Answer 42

surface area to volume ratio = surface area ÷ volume - as particles decrease in size, their surface area to volume ratio increases (the size of their surface area increases in relation to their volume)

Question 43

uses of nanoparticles

Answer 43

**catalysts** - huge surface area to volume ratio **nanomedicine** - tiny particles (e.g. fullerenes) are absorbed much more easily by the body than most particles - could deliver drugs right into the cells where they're needed **electric circuits** - some can conduct electricity, so can be used for electric circuits in computer chips **antibacterial properties** - silver nanoparticles - can be added to polymer fibres that are then used to make surgical masks, wound dressings + can be added to deodorants **cosmetics** - to improve moisturisers without making them really oily

Question 44

effects of nanoparticles on health

Answer 44

aren't fully understood - don't know what the long term effects will be - many people believe products containing nanoparticles should be clearly labelled, so consumers can choose if they want to use them - currently used in sun creams as they have proven to be better at protecting skin from UV rays than materials in traditional sun creams + give better skin coverage than traditional sun creams - not clear yet if the nanoparticles g=can get into your body, and if they do, whether they might damage your cells - possible that when they are washed away they may damage the **environment**