C3 : Structure and Bonding Flashcards
Why are ionic compounds crystals?
Due to their regular structure of the ionic lattice.
- the ions are joined by strong ionic bonds between oppositely charged ions
Why do ionic compounds have high melting/boiling points?
A lot of energy is needed to break the bonds bc they’re very STRONG.
Why can a solid ionic substance NOT conduct electricity but a molten/aqueous ionic substance can? (6)
- When solid, ions are bonded together by the lattice in a fixed position .
- ions cant move to carry the electrical charge
- in liquid, ions can break free from lattice
- able to move, bc supplied with enough energy to become a liquid
- can carry electrical charge
What do ionic bonds form between?
Metal / non-metal - conduct in molten/aqueous state
What do covalent bonds form between?
2 non- metals
- don’t conduct electricity/heat
Why do the simple covalent bonds have low MP/BP?
Bc intermolecular forces are relatively weak - less energy is needed to OVERCOME the forces
Intermolecular forces are weaker than covalent bonds - covalent bonds aren’t broken
compare the strength of bonds between atoms in the molecule to the forces that exist between the different molecules. (2)
The strength of the coaled bonds are stronger Tham the intermolecular forces - they are weak.
Examples of SIMPLE covalent bonds. (3)
H20 - water
CO2 - carbon dioxide
NH3 - ammonia
Examples of giant covalent bonds. (5)
Diamond
graphite
graphene
fullerenes
silicon dioxide
Why do giant covalent bonds have high MP/BP?
- Bc they don’t form molecules
-A lot of energy is needed to break the strong covalent bonds
What are graphite’s properties and why do they have these properties? (3)
Soft/slippery - layers are far apart
- forces between layers are weak
- easy to separate layers /slide
High MP
- difficult to break strong covalent bonds
Conducts Electricity/Heat
- 3 of the 4 outer electrons are held in place in the layer
- the 4th electron is is DELOCALISED. Electron current can be carried/travel through material.
What are allotropes?
Different structural forms of the same element in the same physical state.
what are the allotropes of carbon?
Diamond
Graphite
Graphene
Fullerenes
Why do metals have high BP/MP?
- takes a lot of energy to separate metal ions from fixed positions, as electrostatic forces are very strong
How are ions held together in a metal? (3)
- lattice structure of positive ions
- with delocalised electrons/free electrons
-Strong electrostatic forces between the electrons and + ions bond the metal ions together.
How does the structure and bonding in metals allow them to bent and shaped?
- layers of atoms are able to SLIDE easily over each other
Properties of diamond and uses.
- very hard - lots of covalent bonds
- takes a lot of energy to break these bonds
- giant lattice structure - BAD conductor of ELECTRICITY
- no delocalise electrons
USED FOR : jewellery
cutting tools/blade edges
Properties of graphene. SFC
STRONG - due to strong covalent bonds/unbroken pattern
CONDUCTS ELECTRICITY/HEAT - has free electrons to carry current/heat
3/4 electrons are bonded , 4th Is delocalised
FLEXIBLE - bonds between atoms are flexible
What can fullerenes be used for and what properties allow this?
-can CAGE other molecules - good for DRUG DELIVERY
- large SURFACE AREA - make them good industrial catalysts
WEAK intermolecular forces , so SLIPPERY/LOW MP - lubricants
describe the nature of chemical bonding in ionic strictures? (3)
- giant lattice structure
-held together by strong electrostatic forces between oppositely charged ions
-theses forces act in all directions
why are alloys harder than pure metals?
- atoms/ions/particles are different sizes
- layers can’t slide over eachother
NANOPARTICLES SIZE?
(1X10-9) - (1X10-7)
1nm - 100nm
surface area: volume ration equyation?
SA / VOL
USES OF nanoparticles ?
- high SA:V - CATALYSTS
DRUG DELIVERY - absorbed into body easily
ELECTRIC CIRCUITS - conductor
POLYMER FIBRES - (surgical masks/wound dressing) - ANTIBACTERIAL
COSMETICS
what are effects on health by using nanoparticles?
- jnot sure LONG TERM EFFECTS
- SHld be clearly labelled so consumer can decide whether to use product or not
- could DAMAGE CELLS/DAMAGE ENVIRON
how are nanoparticles able to catalyse reaction?
- A catalyst provides an alternative reaction pathway with lower activation energy
- Often by creating more surface area for reactant particles to collide
- As nanoparticles have a high surface area to volume ratio
- They provide much more surface area for catalytic activity to occur
- Hence increasing the rate of reaction
