bonding,structure and the properties of matter Flashcards
what are the 3 types of strong chemical bonds?
- ionic
- covalent
-metallic
ionic bonding
- particles are oppositely charged ions
- occurs in compounds formed from metals combined with non-metals
in ionic bonding, do metal atoms lose electrons?
- 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
what is an ion?
an atom that has lost or gained an electron/ electrons
what happens to the ions produced in groups 1 and 2 and non-metals in groups 6 and 7 in ionic bonding?
- gain a full outer shell of electrons, same electronic structure as noble gases
dot and cross diagram
- represents an electron transfer during the formation of an ionic compound
dot and cross diagram checklist
- 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
what is an ionic compound?
- 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
covalent bonding
- particles are atoms which share a pair of electrons
- occurs in most non-metallic elements and in compounds of non-metals
what type of molecules have strong covalent bonds within their molecules?
- HCl, H2, O2. Cl2, NH3, CH4
what are polymers?
- large covalently bonded molecules
what do giant covalent structures consist of?
- many atoms covalently bonded in a lattice structure
-e.g diamond and silicon dioxide
how can covalent bonds be represented?
- dot and cross
- single line = single bond
- ball and stick
- 2D or 3D diagrams
metallic bonding
- particles are atoms which share delocalised electrons
- occurs in metallic elements and alloys
what does a metal consist of?
- giant structures of atoms arranged in a regular pattern
delocalised electron system
- 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
three states of matter
- solid
- liquid
- gas
melting point
- where melting and freezing take place
boiling point
- where boiling and condensing take place
particle theory
- 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
what are the limitations of simple models of three states of matter?
- no forces
- all particles represented as spheres
- spheres are solid
aqueous solution
- solution where solvent is water
properties of ionic compounds
- 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
why can ionic compounds conduct electricity when molten/dissolved in water?
as ions are free to move and carry a current
why ca’t ionic compounds conduct electricity when solid
as ions are fixed in place
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
why do larger molecules have higher melting and boiling points?
as intermolecular forces increase with the size of molecules
polymers
- very large molecules
- atoms linked by very strong covalent bonds
- intermolecular forces relatively strong, solid at room temp
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
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
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
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
diamond
- each carbon covalently bonded to 4 other carbon atoms
- giant covalent structure
- very hard
- high melting point
- does not conduct electricity
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
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
what was the first fullerene to be discovered?
buckminsterfullerene
uses of fullerenes
- lubricants
- drug delivery
- catalyst
- reinforcing materials
fullerenes
- molecules of carbon atoms with hollow shapes
- based on hexagonal rings of carbon but may contain rings of five or seven
carbon nanotubes
- cylindrical fullerenes with very high length to diameter ratios
- properties make them useful for nanotechnology, electronics and materials
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
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
coarse particles
- diameters of 0.00001m and 0.000025m
- often referred to as dust
disadvantages of nanoparticles
- may be toxic
- may enter brain from bloodstream and cause harm
what happens when size of a cube decreases by a factor of ten?
the SA to volume ratio increases by ten
