Topic 2 Bonding, Structure And Properties Of Matter Flashcards
What does ionic bonding occur between?
Metals and non-metals
What does covalent bonding occur between?
Non-metals
Where does metallic bonding occur?
In metallic elements and alloys
What are the electrostatic forces of attraction between in an ionic compound?
Oppositely charged ions
What is an ionic compound?
Giant structure of ions
What arrangement do the ions form in an ionic compound?
Regular lattice
What is the structure of an ionic compound called?
Giant ionic lattice
What are the 2 properties of ionic compounds?
- High melting and boiling points
- can conduct electricity when melted/dissolved in water
Why can ionic compounds conduct electricity when melted or dissolved in water?
Ions free to move - can carry charge/charge can flow
Why are covalent bonds strong?
positively charged nuclei of the bonded atoms are attracted to shaired pair of electrons by electrostatic forces
How does the displayed formula represent covalent bonds?
as single lines between atoms
What is a simple molecular substance?
made up of molecules containing a few atoms joined by covalent bonds
What is the formula for ammonia?
NH3
What are 8 examples of simple molecular substances?
- hydrogen
- chlorine
- oxygen
- nitrogen
- methane
- water
- hydrogen chloride
- ammonia
What are 3 ways covalent bonds can be represented?
- dot and cross diagrams
- displayed formula
- 3D model
What are the atoms within molecules in simple molecular substances held together by?
very strong covalent bonds
What are the forces of attraction between molecules in simple molecular substances?
intermolecular forces
What forces are overcome when a simple molecular substance is melted or boiled?
intermolecular forces
Why do simple molecular substances have low melting and boiling points?
weak intermolecular forces are easily overcome
What state are simple molecular substances usually in at room temperature?
gases or liquids
Why do molecular compounds not conduct electricity?
not charged so there are no free electrons or ions
Why do larger molecules have higher melting and boiling points?
as molecules get bigger, the strength of intermolecular forces increases
What are 3 bulk properties of simple molecular substances?
- usually gases/liquids at room temp
- don’t conduct electricity
- low melting and boiling points
What are polymers?
long chains of repeating units
What are the atoms in polymer molecules joined by?
strong covalent bonds
Why are most polymers solids at room temp?
larger intermolecular forces between polymer molecules than between simple covalent molecules so more energy needed to break them
What are all the atoms in giant covalent structures bonded together by?
strong covalent bonds
Why do giant covalent structures have very high melting and boiling points?
lots of energy needed to break strong covalent bonds
What are 3 examples of giant covalent structures?
- diamond
- graphite
- silicon dioxide
In diamond, how many covalent bonds does each carbon atom form?
4 covalent bonds
What are 3 properties of diamond?
- very hard
- very high melting point
- doesn’t conduct electricity
Why is diamond very hard?
carbon atoms each form 4 covalent bonds
Why does diamond not conduct electricity?
no free electrons or ions
Why does diamond have a very high melting point?
strong covalent bonds take a lot of energy to break
In graphite, how many covalent bonds does each carbon atom form?
3 covalent bonds
In graphite, what do the 3 covalent bonds each carbon atom forms, create?
layers of carbon atoms arranged in hexagons
Why can the layers in graphite move over each other?
no covalent bonds between layers - held together weakly
Why is graphite a good lubricating material?
its soft and slippery (layers can slide over eachother)
Why has graphite got a high melting point?
covalent bonds in layers need lots of energy to break
In graphite, why does each carbon atom have one delocalised electron?
only 3 out of carbons 4 outer electrons are used in bonds
Why does graphite conduct electricity and thermal energy?
each carbon atom has one delocalised electron that can move and carry charge
What property of graphene makes it useful in electronics?
Contains delocalised electrons- can conduct electricity through whole structure
What property of graphene makes it useful to add to composite materials?
Strong covalent bonds - very strong but also light
What are fullerenes?
Molecules of carbon with hollow shapes
What was the first fullerene to be discovered?
Buckminsterfullerene
What shape does Buckminsterfullerene have?
Hollow sphere
What is the molecular formula of Buckminsterfullerene?
C(60)
What is the structure of fullerenes?
Mainly made up of hexagonal rings of carbon atoms but can also contain pentagons and heptagons
Why are fullerenes useful in delivering drugs into the human body?
Fullerenes can ’cage’ other molecules
Why do fullerenes make great industrial catalysts?
huge surface area- Individual catalyst molecules can be attached
What are 3 examples of uses of fullerenes?
- deliver drugs into the body
- make lubricants
- make industrial catalysts
What are carbon nanotubes?
Tiny carbon cylinders (fullerenes)
What are 4 properties of carbon nanotubes?
- very high length to diameter ratio
- conduct electricity
- conduct heat
- high tensile strength (don’t break when stretched)
What is nanotechnology?
Technology that uses very small particles such as nanotubes
What are 3 examples of uses of nanotubes?
- in nanotechnology
- in electronics
- to strengthen materials (eg tennis rackets)
Why are nanotubes useful in strengthening materials?
Don’t add much weight
What do metals consist of?
Giant structures of atoms arranged in a regular pattern
Which electrons are delocalised and free to move around in metals?
Outer shell electrons of the metal atoms
What is metallic bonding?
Strong electrostatic attraction between sea of negative delocalised electrons and positive metal ions
What holds the atoms of a metal together in a regular structure?
Electrostatic forces of attraction
Are metallic bonds strong or weak?
Very strong
What are 2 substances that are held together by metallic bonding?
metallic elements and alloys
Why are most metals solid at room temperature?
Have high melting and boiling points
What do most metals have high melting and boiling points?
Strong metallic bonds- lots of energy to be broken
Why are metals good conductors of electricity?
Delocalised electrons carry charge through whole structure
Why are metals good conductors of thermal energy (heat)?
Energy transferred by delocalised electrons
Why are most metals malleable?
Layers of atoms can slide over each other- metals can be bent or shaped
Why are pure metals mixed with other metals?
Too soft for many uses so mixed with other metals to make alloys which are harder
What are alloys?
Mixture of two or more metals or a metal and another element
Why are alloys harder than pure metals?
- different elements have different sized atoms
- new metal atoms distort layers of metal atoms- harder for layers to slide over each other
What are the 2 limitations of the particle theory model?
- there are no forces shown (no way of knowing their strength)
- particles represented as solid inelastic spheres (instead of atoms, ions or molecules)
What are the categories particles are put in based on?
Their diameter
What are the diameters of nanoparticles?
1-100nm
What is nanoscience?
area of science that investigates uses and properties of nanoparticles
What are the diameters of fine particles?
100-2500nm
What are the diameters of coarse particles?
2500-10000nm
What are coarse particles also referred to as?
Dust
What is the main property of nanoparticles?
Large surface area to volume ratio
What happens to the surface area as particles decrease in size?
Surface area increases in relation to their volume- surface area to volume ratio increases
What is the equation to find the surface area to volume ratio?
Surface area to volume ratio = surface area/volume
What is the rule for surface area to volume ratio as particles decrease in size?
As the side of a cube is decreased by factor of 10, surface area to volume ratio increases by factor of 10
What causes the properties of a material to be different if it’s a nanoparticle rather than in bulk?
Nanoparticles have a high surface area to volume ratio
Why are smaller quantities of a material made up of nanoparticles needed to work as an effective catalyst than for materials made up of ‘normal’ sized particles?
Nanoparticles have a high surface area to volume ratio
What are 6 applications of nanoparticles?
- as catalysts
- in medicine
- in electronics
- in cosmetics
- in sun creams
- in deodorants
What is a disadvantage of nanoparticles?
Effects of nanoparticles on human health isn’t fully understood
