Topic 2 - bonding ,structure and properties of matter Flashcards
what are ions
charged particles
what ions do metals and non metals form
metals - positive
non metals - negative
what is an ionic bond
when a metal and a non metal react together, the metal atom loses electrons to form a positively charged ion and he non metal gains these electrons to form a negatively charged ion . these oppositely charged ions are strongly attracted to one another by electrostatic forces. this attraciton is an ionic bond
what are the advantages and disadvantages of dot and cross diagrams
useful for showing how ionic compounds are formed
dont show the structure of a compound , the size of ions or how they are arranged
what is the structure of ionic compounds
giant ionic lattice
the ions form a closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between the oppositely charged ions in all directions of the lattice
what are the properties of ionic compounds
high melting points and high boiling points due to the many strong bonds between the ions. it takes a lot of energy to overcome this attraction.
when they are solid, the ions are held in place so the compounds cant conduct electricity, when ionic compounds melt , the ions are free to move aroun and they will carry electric charge. some ionic compounds also dissolve in water, the ions seperate and are all free to move in the solution so they will carry electric charge.
what are the steps to writing an emprirical formula of an ionic compound
work out the ions
work out the charges
balance the charges so the charge of the empirical formula is zero
what are covalent bonds
when non metal atoms bond together , they share pairs of electrons
the positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces, making covalent bonds very strong
what ar ethe advantages and disadvantages of dot and cross diagrams
useful for showing whih atoms the electrons in a covalent bond come from , but they dont show the relative sizes of the atoms or how the atoms are arranged in space.
what are the advantages and disadvantages of a displayed formula
shows how atoms are connected in large molecules.
they dont show how the 3d structure of the molecule or which atoms the elextrons in the covalent bond have come from .
what are simple molecular substances and name the ones you need to know
made up of molecules containing a few atoms joined together by covalent bonds
hydrogen h2
chlorine cl2
oxygen o2
methane ch4
water h2o
hydrogen chloride hcl
what are the properties of simple molecular substances
substances containing covalent bonds usually have simple molecular structures
the atoms withing the molecules are held together by very strong covalent bonds, in contrast the forces of attraction between the molecules are very wweak .
to melt or oboil a simple molecular compound you only need to break the weak intermolecular frces not the covalent bond so the melting and boiling points are very low.
most are gases or liquid at room temperature.
as they get bifger, the strength of the intermolecular forces increases so more energy is needed to break them , and so the boiling an melting point increases.
dont conduct electricity as there are no free elecctrons or ions
what are polymers and what are their properties
in a polymer, lots of small units are linked together to form a long molecule that has repeating secions.
all the atoms in a polymer are joinned by strong covalent bonds
intermolecular forces are larger than between simple covalent molecules so more energy is required to break them
solid at room temperature
lower boiling points than ionic or giant molecular compounds.
describe what giant covalent structures are like and give three examples
all the atoms are bonded to each other by strong covalent bonds
very high melting and boiling points .
dont contain charged particles so they dont conduct.
diamond - each carbon atom forms gour covalent bonds in a very rigid giant covalent structure
graphite - each carbon atom forms three covalent bonds to create layors of hexagons , each carbon atom also has on delocalised electron
silicon dioxide sometimes called silica -what sand is made of
describe the properties of each of the alotropes of carbon
diamon - giant covalent structure mae up of carbon atoms that each form four covalent bonds . this makes diamond really hard.
strong covalent bonds require a lot of energy to break and give diamond a high melting point.
doesnt conduct electricity as it has no free electrons .
graphite- each carbon is bonded to three others creating sheets of carbon atoms arranged in hexagons.
there arent covalent bonnds between the layers 0 they are held together weakly so they are free to slide over eachother. this makes graphite soft and slippery so its ideal for lubricants.
high melting point - covalent bonds need energy to break
delocalised electrons that can move through the structure carruing a charge
conducts
graphene - a sheet of graphite
one atom thick
the network of covalent bonds makes it very strnng and incredibally light.
can be added to composite materials to improve their strenght
cam conduct and therefore be used in electronics
fullerenes - molecules of carbon shaped like closed tubes or hollow balls
buckminster fullerene was the first fullerene to be discovered , it forms a hollow sphere
mainliy made up of carbon atoms arranged in hexagons but can alos contain pentagons or heptagons.
can be used to cage other molecules. the fullerene strucute forms around another atom or molecule which is then trapped inside. this can be used to deliver drugs.
have a huge surface area so can be used as catalysts
can be used as lubricants
can form nanotubes 0 tiny carbon cylinders
the ration between lenth and diameter of nanotubes are very high
conducts
high tensile strenght
can be used in electronics or to strenghten materials without adding weight like tennis rackets.
describe the structure and bonding of metals
metals consits of a giant strucure
the electrons in the outer shell of the metal atoms are delocalised . there are strong forces of electrostatic attraction between the positive metal ions and the shared negative electrons.
these forces of attraction hold the atoms together in a regular structure and are known as metallic bonding . metallic bonding is very stron
substances that are held together by metallic bonding include metallic elements and alloys
the delocalised electrons in the metallic bonds bproduce all properties of metals
describe the properties of metals
high melting points - the electrostatic forces between the metal aroms and the delocalised sea of electrons are very strong aso needs a lot of energy to be broken .
the delocalised electrons carry charge through the whole structure so metals are good conductores of heat and electricity
the layers of atoms in a metal can slide over each other making metals malleable
what are alloys and why do we need them
pure metals are too soft so are mixed with others to make them harder .
different elements have different sized atoms . so when another element is mixed with a pure metal , the new metal atoms will distort the laters of metal atoms making it more difficult for them to slide over each other. this makes allots harder than pure metals.
what does how strong the forces of attraction are depend on
the material
the temperature
the pressure
describe the three states of matter
solid - strong forces of attraction between the particles, whcih holds them close together in fixed positions to form a very regular lattice arrangement
the particles dont move from their positions, so all solids keep a definite shape and volume and dont flow like liquids.
the particles vibrate about htier positions - the hotter the solid becomes , the more they vibrate (causing them to expand slightly)
liquids - weak force of attraction between the particles. they are randomly arranged and free to move past eachother, but they tend to stick closely together.
liquids will have a definite volume but dont keep a desinite shape and will flow to fill the bottom of a container.
the particles are contrantly moving with random motion. the hotter the liquid the faster they move.
gases - the force of attraction between the particles is very weak - they are free to move around and are far apart. the particles travel in stright lines.
gases dont give a definite shape or volume and will always fill any container.
the particles move constantly with random motion. the hotter the gas, the faster they move
what are the advantages and disadvantages of the particle theory
explains the three states of matter
the particles in realitiy arent solid, inelastic spheres , they are atoms, ions and molecules.
doesnt show the forces between the particles, no way of knowing how strong they are.
describe all of the physical state changes that substances can go through .
when a solid is heated its particles gain more energy - this makes the particles vibrate more which weakens the forces that hold the solid together - at a certain temperature called the melting point , the particles have enough energy to break free grom their positions. this is called melting and the solid turns into liquid - when a soling is heated again , the particles get even more energy - this energy makes the particles move faster, which weakens and breaks the bonds holding th eliquid together. - at a certain temperature , called the boiling point, the particles have enough energy to break their bonds, this is boiling or evaporating . the liquid becoems gas - as a gas cools , the particles no longer hace enough energy to overcome the forces of attraciotion 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 . ths is called condensing . - when a liquid cools, the particles have less energy so move around less.- there is not enough nergy to overcome the attraxtion between the particles , so more bonds form between them . - at the melting point, so many bonds have formed between the particles that theyre held in place. the liquid becomes solid , this is freezing
what are the different catergories of particles
coarse particles - diameter between 2500 nm and 10 000 nm
dine particles diameter between 100nm and 2500 nm
nanoparticles have a diameter between 1 nm and 100 nm
what happens to surface area as a particle decreases in size
its surface are increases in relation to volume
