Structures and bonding Flashcards
Name the properties of simple covalent molecules
- Low melting and boiling points
- Usually gases at room temperature
(except water) - Don’t conduct electricity
Explain the properties of simple covalent bonds
- Low melting and boiling points as they are held together by weak intermolecular forces which require little energy to break
- Don’t conduct electricity as their molecules have no overall charge
Why can’t simple covalent molecules conduct electricity?
- Don’t conduct electricity as their molecules have no overall charge
Why do simple covalent molecules have low melting and boiling points?
- They’re held together by weak intermolecular forces which require little energy to break
Name the properties of giant covalent structures
- Solid at room temperature
- High melting and boiling points
Name 4 giant covalent structures
Diamond, Silicon Dioxide, Graphite and Graphene
Describe and explain the properties of Diamond
- Formed from carbon bonded to itself 4x
- High melting and boiling points as they have a large
number of strong covalent bonds that are hard to break - Can’t conduct electricity as there are no free electrons
to carry charge
Why do giant covalent structures have high melting and boiling points while simple covalent molecules don’t?
As the size of the molecule increases, the intermolecular forces get stronger.
Describe and explain the properties of Silicon Dioxide
- Silicon bonded to oxygen
- High melting and boiling point due to large number
of strong covalent bonds
Describe and explain the properties of graphite
- Carbon bonded to itself 3 times
- High melting and boiling point due to a large number
of strong covalent bonds - Soft and slippery as there are no covalent bonds
between its layers/lattices - Good conductors of heat and electricity as they have
delocalised electrons.
Explain why graphite can conduct electricity and heat
In every graphite molecule, there is one electron not covalently bonded, these are released from the atom, and are called delocalised electrons. These electrons can move, so graphite can conduct heat and electricity
How many times is carbon bonded to itself in graphite and diamond?
Graphite - 3x
Diamond - 4x
What is graphene?
A single layer of graphite
What is a use of graphite?
A lubricant
Describe the structure of graphite
Layers of carbon atoms in hexagonal rings
Describe and explain the properties of graphene
- One atom thick (a single layer of graphite)
- Good conductor as it contains delocalised electrons
- Very strong
What are fullerenes?
Molecules of carbon atoms with hollow shapes, they are usually formed with hexagonal rings
What are some uses of fullerenes?
- Pharmaceutical deliveries (into the body)
- Lubricants
- Catalysts
What are carbon nanotubes?
Fullerenes shaped into long cylinders with a high length to diameter ratio
- Used in electronics, nanotechnology and materials
Describe the properties of carbon nanotubes
- High tensile strength (can be stretched without
breaking) - Good conductors of heat and electricity
Give one use of carbon nanotubes
To reinforce materials e.g. Tennis rackets
What are nanoparticles?
Particles with a diameter between 1-100nm that only contain a few hundred atoms
What is the relative size of a coarse particle (PM10)
Diameter between 1x10⁻⁵m and 2.5x10⁻⁶m
-They contain many thousands of atoms
What is the relative size of a fine particle?
Diameter between 100 and 2500nm
1x10⁻⁷m and 2.5x10⁻⁶m
Contain several thousand atoms
Describe the relationship between particle size and surface area : volume ratio
As the particle size decreases by 10x, the surface are to volume ratio increases by 10x
Why are nanoparticles useful in chemical reactions?
They have a high surface area : volume ratio meaning that a smaller quantity is required than if a larger particle were to be used
What are some uses of nanoparticles?
- Medicines
- Sun creams
- Cosmetics
- Deodorants
- Electronics
- Catalysts
What is a risk of using nanoparticles in products like sun creams?
It is possible that nanoparticles can be absorbed into the body and enter body cells. The potential long term effects of this are unknown.
Describe the structure and bonding in Sodium Chloride (4)
- It’s a giant ionic structure/lattice
- Containing ions
- Na+ and Cl-
- Held together by the electrostatic force
Why might sock manufacturers use silver nanoparticles in their socks?
To remove odour/kill bacteria or microorganisms
Why might some people be worried wearing clothes made with nanoparticles?
nanoparticles / ions might penetrate skin and get into bloodstream, where they could accumulate in organs, possibly causing health issues.
What are the 5 uses of nanoparticles?
- Sunscreens
- Cosmetics
- Deodorants
- Electronics
- Catalysts
Why are nanoparticles more effective than normal sized particles?
They have a high surface area:volume ratio, and therefore less is required to produce the same/a similar effect.
Describe the structure of a metal and why it can conduct electricity when solid (3)
- They contain many positive ions surrounded by a sea of
electrons, which can move throughout the structure and
carry charge
Why are ball and stick diagrams not true representations of ionic compounds?
The ions should be touching and shouldn’t have gaps between them
Why is it called the periodic table?
Similar properties occur at regular intervals
