2.1 BONDING, STRUCTURE AND PROPERTIES Flashcards
WHAT HOLDS METALS TOGETHER?
Strong electrostatic attraction between positive metal ions and negative electrons
WHAT ARE THE TYPICAL PROPERTIES OF A METAL?
- Strong
- High melting point
- Good electrical conductivity
- Malleable
- Ductile
- Insoluble
- Shiny
HOW DOES IONIC BONDING OCCUR?
The outer electrons of a metal are transferred to the outer electron shell of a non-metal
WHY DOES IONIC BONDING OCCUR?
To complete their outer shells and become stable
HOW CAN WE SHOW IONIC BONDING?
Electron transfer diagrams
HOW DO COVALENT BONDS FORM?
Non-metal atoms share their outer electrons in order to complete their outer shell and become stable
WHAT IS A COVALENT BOND?
A shared pair of electrons
HOW DO WE SHOW COVALENT BONDS?
Dot-and-cross diagrams
WHAT ARE THE PROPERTIES OF A SIMPLE COVALENT STRUCTURE?
- Low melting and boiling points
- Poor conductors of electricity
- Variable solubility in water
HOW MANY OF THE CARBON ATOMS ARE COVALENTLY BONDED IN DIAMOND?
All 4
WHAT ARE THE PROPERTIES OF DIAMOND?
- Very high melting point – strong covalent bonds that need a lot of energy to break.
- Very hard – again due to strong covalent bonds.
- Electrical insulator – diamond does not have any free electrons so is not a conductor of electricity
HOW MANY OF THE CARBON ATOMS ARE COVALENTLY BONDED IN GRAPHITE?
Only 3 of the 4 carbon atoms present
WHAT ARE THE PROPERTIES OF GRAPHITE?
- Very high melting point – strong covalent bonds that require a lot of energy to break.
- Soft and slippery to the touch – the atoms within each layer are held together by strong covalent bonds but the layers themselves are held together by weak intermolecular forces. This means the layers of carbon atoms can easily slide over each other when a force is applied.
- Good conductor of electricity – the delocalised electrons between the layers can carry electrical energy.
WHAT ARE THE USES OF CARBON FULLERINES?
- Drug delivery
- Lubricant
- Catalyst
WHAT IS THE MOST COMMON FULLERINE?
Buckminsterfullerene
WHAT ARE THE PROPERTIES OF NANOTUBES?
- Very strong
- Soft and slippery to the touch
- Very good conductor of electricity
WHAT ARE THE PROPERTIES OF GRAPHINE?
- Very strong (up to 300 times stronger than steel)
- Best conductor of electricity known
WHAT IS A SMART MATERIAL?
A material that has at least one property that changes reversibly when their environment changes in a certain way
WHAT ARE THERMOCHROMIC PIGMENTS AND WHAT ARE THEIR USES?
Materials that change their colour when they reach a specific temperature.
Uses:
- colour changing mugs, battery power indicators, bath toys for children, and strip thermometers.
WHAT ARE PHOTOCHROMIC PIGMENTS AND WHAT ARE THEIR USES?
They change colour with light intensity (particularly ultraviolet light intensity).
Uses:
- dyes in clothing and lenses in glasses that darken in bright sunlight.
WHAT ARE SHAPE MEMORY POLYMERS AND WHAT ARE THEIR USES?
Plastics that return to their original shape when heated.
Uses:
- car bumpers, medical sutures (‘stitches’) and sports equipment such as helmets and gumshields
WHAT ARE SHAPE MEMORY ALLOYS AND WHAT ARE THEIR USES?
Metal alloys that return to their original shape when heated.
Uses:
- deformable spectacle frames, surgical wires to replace tendons and surgical plates for joining bone fractures
WHAT ARE HYDROGELS AND WHAT ARE THEIR USES?
Polymers that can absorb up to 1000 times their own volume in water when surrounded by water.
Uses:
- filling of nappies to absorb more urine without leakage and granules added to house plant compost to retain more water and release it over a long period of time
HOW BIG ARE NANOPARTICLES?
between 1 and 100 nanometres (nm) in size
