Covalent Bonding, Metallic Bonding and Ionic bonding, Properties of metals, nanoparticles Flashcards
What is covalent bonding?
When atoms share pairs of electrons. (strong bond)
Advantages of displayed formula
- quick and easy to draw and identify
- shows how they are bonded to each other
Advantages of ball and stick models
- shows the shape of the molecule
- 3D
- shows which atoms are bonded to which
Advantages of dot and cross diagrams
- shows which atoms are bonded to each other
- shows electrons
Disadvantages of displayed formula
- 2D
- cannot see electrons
Disadvantages of ball and stick models
- does not show electrons
- hard to draw when there are many atoms
Disadvantages of dot and cross diagrams
- does not show electrons orbiting
- hard to draw if there are many atoms
- 2D
Size of atom
1 nanometer (1x10^-9m)
Size of nucleus
About 1x10^-14m
Difference between simple and giant covalent structures
simple covalent structures have a fixed number of atoms (eg. ammonia) and giant covalent structures have large and variable amounts of atoms
Properties of giant covalent structures
- high boiling and melting points (strong intermolecular forces)
- strong (covalent bonds)
- cannot conduct electricity (except for graphite and graphene)
- has a lattice structure
- not soluble in water
Properties of simple covalent molecules
- low boiling and melting points
- weak intermolecular forces
- do not conduct electricity as they do not have an overall electric charge
What are polymers?
large molecules with many small repeating units called monomers that are joined with strong covalent bonds
What is graphene?
A single layer of graphite
Properties of graphene
- very high melting point
- very strong
- conducts electricity well due to having delocalised electrons
- often used in electronics and composites
What are fullerenes?
- Molecules of carbon atoms with hollow shapes
- based on hexagonal rings of carbon atoms but may also contain rings of five or seven carbon atoms
What was the first fullerene that was discovered?
Buckminsterfullerene (C60)
Properties of fullerenes
- low melting and boiling point (weak intermolecular forces
- cage like structure (can transport substances inside it eg. medicine)
- good catalyst (large surface area compared to volume)
- has a delocalised electron that can carry the charge
- lightweight
Are the intermolecular forces of polymers strong
yes, so they remain as solids at room temperature
How is ethene converted to polyethene?
the double covalent bond between the carbon atoms are broken and is joined to a neighboring molecule
Draw the shorthand way of representing a polymer
(see goodnotes)
Compare diamond to graphite
(see notability)
Where do we find metals on the periodic table?
on the left
What is metallic bonding?
- A strong electrostatic force of attraction between positive and delocalised electrons
- the delocalised electrons are free to move through (not throughout) the whole structure, leaving positive ions.
- positive metal ions surrounded by sea of delocalised electrons
Advantages of the 2D diagram of metallic bonding
- can see the “sea” of electrons
- can see every atom easily (none are blocked or covered)
Advantages of the 3D diagram of metallic bonding
- shows layer arrangement of the atoms and the giant lattice structure
Disadvantages of the 2D diagram of metallic bonding
- cannot see the layer arrangement of the atoms/ the giant lattice structure
- doesn’t show each indivual electron
Disadvantages of the 3D diagram of metallic bonding
- doesn’t show electrons at all
- can only see outermost atoms
Properties of metals
- high melting and boiling point: strong electrostatic forces of attraction so it takes a lot of thermal energy to break the bond
- malleable: metals consist of layers of ions that are the same size that can slide over each other when the metal is bent, hammered, or pressed
- electrical conductor: delocalised electrons can carry electrical charge through the metal and move through the structure
Why are alloys stronger and harder than pure metals
- the layers are distorted so the particles cannot slide over each other as well
Why do alloys not conduct as well as pure metals
- distorted layers cause the delocalised electrons to not be able to move through the structure as easily.
Describe ionic bonding
the metal atom loses its outermost electrons and transfers them to the non metal atom to complete the non metal atom’s outer shell. This makes the metal atom a positive ion and the non metal atom a negative ion as there aren’t enough electrons to balance the charge of the protons and vice versa. there is a strong electrostatic force of attraction between the oppositely charged ions
Properties of ionic compounds
- high melting and boiling point : the lattice structure and the strong electrostatic forces between the ions require a lot of thermal energy to break
- Crystalline : this reflects the regular arrangement of teh ions
- brittle : small distortions in the crystal bring ions with the same charge together and similar charges repel each other, breaking the crystal apart
- soluble in water : the slightly negative oxygen in the water attracts the positive ions while the slightly negative hydrogen in the water attracts negative ions, pulling the crystal apart
- do not conduct when solid : the ions cannot move when the ionic compound is solid there cannot carry any charge and cannot conduct electricity
- conduct when molten/ in solution : the ions are free to move when molten or dissolved and will carry the charge and conduct electricity
Draw a ionic bonding diagram for sodium chloride
see goodnotes
What does the particle model of the three states of matter assume?
1) there are no forces between the particles
2) all particles in a substance are spherical
3) spheres are solid
What are fullerenes usually used for?
- lubricants
- drug delivery
Why do nanoparticles have different properties to bulk materials of the same substance?
- high surface area to volume ratio
What are nanoparticles used for?
- healthcare, electronics, cosmetics, and as catalysts
What is the size of the structures that nanoscience refers to?
structures that are 1-100 nm in size
(a few hundred atoms)
How does the surface area to volume ratio change when the side of a cube decreases by a factor of 10?
it increases by a factor of 10
What is the diameter of a coarse particle?
also refered to dust
1 x 10^-5m - 2.5 x 10^6 m
What is the diameter of a fine particle?
1 x 10^-7 m and 2.5 x 10^-6 m
or 100-2500 nm
Which type of particle is the smallest?
nanoparticle < fine particle < coarse particle
What is 1nm in m?
1 x 10^-12m
What is an application of nanoparticles in fabrics?
- nanosilver woven into fabric to give anti-microbial properties
- nano-titanium used to add sun protection to clothing
What are the benefits of using nanoparticles in fabrics?
- fends off bacteria that makes clothes smell after you sweat
- adds sun protection (also used in sunscreen)
What are the disadvantages of using nanoparticles in fabrics?
- little known about effects of exposure to nanosilver for human body
- nanosilver washes off clothes-> goes into wash water -> goes into sewage sludge/ biosolids that are treated for use
What is an application of nanoparticles in medicine?
- silver nanoparticles used to coat dressings + make surgical masks
- antimicrobial properties
What are the benefits of using nanoparticles in medicine?
- incrediably small = can penetrate cell walls = makes them ideal to deliver drugs to cancer patient
What are the potential disadvantages of using nanoparticles in medicine?
- unaware of long term effects in body
- small enough to penetrate blood brain barrier
- may be toxic to brain
What is an application of nanoparticles in electronics?
- nanotubes conduct small electrical circuits for computers
- allows display screens to be very thin
What are the benefits of using nanoparticles in electronics?
- decreases power consumption + weight
- reduces size in translators and ICs
What are the potential disadvantages of using nanoparticles in electronics?
- could harm environment at disposal
What is an application of nanoparticles in cosmetics?
- used in creams, deodrants + suncreams
What are the benefits of using nanoparticles in cosmetics and suncreams?
- can be absorbed much deeper into the skin
- absorbs UV light better = stops UV light penetrating into skin
What are the potential disadvantages of using nanoparticles for cosmetics?
- breathing in particles could affect lungs
- could accumulate in organisms = unaware of effects
- possible skin damage
What are the applications of nanoparticles in catalysts?
- speeds up reaction without being used up
- platinum in fuel cells
What are the benefits of using nanoparticles in catalysts?
- large SA to volume ratio allows them to catalyse reactions effectively
What are the potential disadvantages of using nanoparticles in catalysts?
- may catalyse harmful reactions in the body
