bonding,structure and the properties of matter Flashcards
(45 cards)
1
Q
what are the 3 types of strong chemical bonds?
A
- ionic
- covalent
-metallic
2
Q
ionic bonding
A
- particles are oppositely charged ions
- occurs in compounds formed from metals combined with non-metals
3
Q
in ionic bonding, do metal atoms lose electrons?
A
- yes to become positively charged ions and vice versa with non-metals
- in ionic bonding, electrons in the outer shell of the metal atom are transferred
4
Q
what is an ion?
A
an atom that has lost or gained an electron/ electrons
5
Q
what happens to the ions produced in groups 1 and 2 and non-metals in groups 6 and 7 in ionic bonding?
A
- gain a full outer shell of electrons, same electronic structure as noble gases
6
Q
dot and cross diagram
A
- represents an electron transfer during the formation of an ionic compound
7
Q
dot and cross diagram checklist
A
- must have square brackets
- clear distinction what electron from which is passed
- labelled at the bottom with word and ion symbol
- show ion symbol outside square brackets
8
Q
what is an ionic compound?
A
- a giant structure of ions
- held together by strong electrostatic forces of attraction between oppositely charge ions
- 3D structure = forces act in every direction
-e.g sodium chloride
9
Q
covalent bonding
A
- particles are atoms which share a pair of electrons
- occurs in most non-metallic elements and in compounds of non-metals
10
Q
what type of molecules have strong covalent bonds within their molecules?
A
- HCl, H2, O2. Cl2, NH3, CH4
11
Q
what are polymers?
A
- large covalently bonded molecules
12
Q
what do giant covalent structures consist of?
A
- many atoms covalently bonded in a lattice structure
-e.g diamond and silicon dioxide
13
Q
how can covalent bonds be represented?
A
- dot and cross
- single line = single bond
- ball and stick
- 2D or 3D diagrams
14
Q
metallic bonding
A
- particles are atoms which share delocalised electrons
- occurs in metallic elements and alloys
15
Q
what does a metal consist of?
A
- giant structures of atoms arranged in a regular pattern
16
Q
delocalised electron system
A
- consists of electrons ‘lost’ from atoms to form positive ions
- free to move through the whole structure
- shared through the structure so metallic bonds are strong
17
Q
three states of matter
A
- solid
- liquid
- gas
18
Q
melting point
A
- where melting and freezing take place
19
Q
boiling point
A
- where boiling and condensing take place
20
Q
particle theory
A
- amount of energy needed to change state from solid to liquid and liquid to gas depends on the strength of forces between the particles of the substance
- The nature of particles involved depends on type of bonding and structure of the substance
- stronger forces between particles = higher melting and boiling point of substance
21
Q
what are the limitations of simple models of three states of matter?
A
- no forces
- all particles represented as spheres
- spheres are solid
22
Q
aqueous solution
A
- solution where solvent is water
23
Q
properties of ionic compounds
A
- regular structures (giant ionic lattice) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions
- high melting and boiling points, lots of energy need to break many strong bonds
24
Q
why can ionic compounds conduct electricity when molten/dissolved in water?
A
as ions are free to move and carry a current
25
why ca't ionic compounds conduct electricity when solid
as ions are fixed in place
26
properties of small molecules
- usually gas or liquid
- low melting and boiling points
- weak intermolecular forces between molecules, which are broken in melting/boiling
- don't conduct electricity as they do not have an overall charge
27
28
why do larger molecules have higher melting and boiling points?
as intermolecular forces increase with the size of molecules
29
polymers
- very large molecules
- atoms linked by very strong covalent bonds
- intermolecular forces relatively strong, solid at room temp
30
giant covalent structures
- solids with very high melting points
- all atoms linked by strong covalent bonds
- bonds must be overcome to melt/boil these substances
- e.g diamond and silicon dioxide
31
properties of metals
- giant structures of atoms with strong metallic bonding
- most have high melting and boiling points
- layers of atoms in metals are able to slide over each other
- metals can be bent and shaped
32
alloys
- a mixture/combination of two or more elements, at least one of which is a metal
- different sized atoms distort layers in structure making it harder for them to slide over each other
- makes alloys harder than metals
33
why are metals good conductors?
- good conductor of electricity as delocalised electrons in metal carry electrical charge
- good conductor of thermal energy as energy is transferred by the delocalised electrons
34
diamond
- each carbon covalently bonded to 4 other carbon atoms
- giant covalent structure
- very hard
- high melting point
- does not conduct electricity
35
graphite
- each carbon covalently bonded to 3 other carbons forming layers of hexagonal rings which have no covalent bonds between layers
- layers can slide, weak intermolecular forces
- soft and slippery
- one electron from each carbon atom is delocalised
- can conduct electricity
36
graphene
- single layer of graphite
- properties useful in electronics and composites
- graphene is strong as layers are tightly bonded
- elastic as planes of atoms can flex relatively easily without atoms breaking apart
36
what was the first fullerene to be discovered?
buckminsterfullerene
36
uses of fullerenes
- lubricants
- drug delivery
- catalyst
- reinforcing materials
37
fullerenes
- molecules of carbon atoms with hollow shapes
- based on hexagonal rings of carbon but may contain rings of five or seven
37
carbon nanotubes
- cylindrical fullerenes with very high length to diameter ratios
- properties make them useful for nanotechnology, electronics and materials
38
nanoparticles
- 1-100 nm across
- contain few hundred atoms
- smaller than fine particles 100 and 2500nm
- have different properties to the 'bulk' chemical it's made from bcoz of their high SA to volume ratio
38
nanoparticle uses
- high SA to volume = good catalyst
- new cosmetics e.g sun cream and deodorant = no white
- lubricant coatings = reduce friction = used for artificial joints and gears
- conduct electricity = use in small electrical circuits for computers
39
coarse particles
- diameters of 0.00001m and 0.000025m
- often referred to as dust
39
disadvantages of nanoparticles
- may be toxic
- may enter brain from bloodstream and cause harm
39
what happens when size of a cube decreases by a factor of ten?
the SA to volume ratio increases by ten
