2. Bonding, Stucture and The Properties of Matter Flashcards
How do elements react?
They form bonds with each other after they’ve reacted, share electrons, or gain/lose outer electrons.
What do ionic compounds contain?
Metal and non-metal atoms
What do covalent compounds contain?
non-metal atoms only
What is an ionic bond?
Attraction between oppositely charged ions
What is a covalent bond?
Two shared electrons between two atoms
Why do ionic compounds conduct when molten or as a solution?
- They’re liquids so ions can move freely
* They have charged particles which pass on the energy
Why do elements react together?
Because they gain or lose outer electrons to get a full outer shell
Why do ionic compounds have high melting/boiling points?
Because there’s a strong bond between ions and need a lot of energy to be broken
What properties do particles need to have to conduct electricity?
- particles must be able to move freely
* particles must have a charge
Why don’t simple covalent substances conduct electricity?
Because they don’t lose/gain electrons - only share them - so there are no charged particles to conduct the energy
Why do simple covalent substances have low melting/ boiling points?
Because the intermolecular forces are weak even though covalent bonds are strong
What are macromolecules?
Giant covalent structures
Does diamond conduct?
No because there are no charged particles to carry the charge
What are diamond’s melting and boiling points like?
High because they have covalent bonds only which are hard to break
How many carbon atoms is each one covalently bonded to in diamond?
4
Why is diamond hard to break?
Because they are all covalent bonds - no intermolecular forces
Does graphite conduct?
Yes because there is one free electron which is free to move per molecule
What is graphite’s boiling and melting point like?
High because it has covalent bonds and intermolecular forces
Which has a lower melting point, graphite or diamond? Why?
Graphite because it only has 3 covalent bonds per atom (diamond has 4 per molecule)
Why is diamond the hardest substance on earth?
It has all covalent bonds
Why is graphite soft and slippery?
Because the layers can glide over each other because the weak intermolecular forces are easily broken
Formula of buck minster fullerene?
C60
How are the carbon atoms bonded in buck minster fullerene?
Each carbon atom bonds to 3 others with two forming single bonds and one a double bond
What does silicon dioxide have a similar structure to?
Diamond
What structure do diamond and silicon dioxide have?
tetrahedral
Particles in ionic compounds?
Ions
Particles in metallic compounds (metallic bonding)?
Positive ions and delocalised electrons
Particles in giant covalent compounds?
Atoms
Particles in simple molecular covalent compounds?
Molecules
What bonds atoms together in metals?
The strong electro-static attraction between negatively charged electrons and positively charged atoms
How are the ions arranged in a metal?
In regular layers
Properties of metals?
- Shaped because the layers slide over each other
- Conducts as outer electrons are delocalised
- High melting point as thee are strong bonds between ions and electrons
What are alloys?
Mixtures where other atoms are added to metals
Why are alloys stronger than pure metal?
The layers are irregular so it’s harder for atoms to slide over eachother
What is ethane an example of?
A monomer
What is polyethane an example of?
A polymer
What are monomers?
Small molecules
What are polymers?
Large molecules
How do polymer chains slide past each other?
Due to weak intermolecular forces
What is graphene?
A thin layer of carbon
What do several layers of graphene form?
Graphite
What are fullerenes?
Larges molecules of allotropes of carbon arranged in balls, cages or tubes
What was the first fullerene discovered?
Buckminster Fulllerene
What are fullerenes used for?
- drug delivery systems
- lubricants
- catalysts
- sports equipment
An example of a fullerene?
Carbon nanotubes
Properties of carbon nanotubes?
High electrical conductivity and are strong and flexible
How big are nanoparticles?
Between 1 and 100nm
atom radius = 0.1nm
Advantages of nanoparticles?
- high sa/v ratio so can react quickly
- make materials stronger and lighter
- save lives
- antibacterial properties
- target specific cells
Disadvantages of nanoparticles?
- could be toxic
- could enter blood stream and cause harm
- speed up reactions in unpredictable ways
- physical handling is hard in liquid or dry forms
Uses of nanoparticles?
- sports equipment- tennis rackets, golf clubs, shoes
- clothing - silver nanoparticles added to socks to absorb smell
- sunscreens - offer protection and can be rubbed in so no white marks
- cosmetics - some contain ‘liposmos’ (fatty nanoparticles)
- house paint and certain candy-coated chocolates - titanium dioxide are so small they don’t reflect visible light
What state is a substance at melting point or above?
Liquid
What state is a substance at boiling point or above?
Gas
