C2.2- structure and bonding Flashcards
Explain the properties of the giant covalent structure- diamond
4 strong covalent bonds per carbon atom
Very strong and high melting point
Explain the properties of the giant covalent structure- graphite
Layers
3 strong covalent bonds per carbon atom
Can conduct electricity
Why are pure metals malleable?
They have ordered rows which can easily slide over each other
Why are pure metals good conductors of electricity and heat?
Delocalised electrons can carry kinetic energy and current
Why do ionic compounds have such high melting points?
Strong electrostatic attraction between + and - ions
What are the properties of a fullerene?
Formula is C60
Simple covalent molecule
Low melting and boiling points
Why are alloys harder than pure metals?
Different sized atoms distort the regular rows, meaning that the layers cannot slide over each other as easily
What is a smart alloy?
An alloy that changes the properties in different conditions
Can ionic compounds conduct electricity? Explain?
Yes but only when it is a liquid because the ions are free to move and carry charge
What size are nanomaterials?
100s of atoms
What is an advantage and a disadvantage of nanoparticles
Advantage- they save resources
Disadvantage- they may be toxic (they can pass through skin)
Why do thermosoftening polymers have low melting points?
They have weak forces between chains
Why do thermosetting polymers have a much higher melting point?
They have cross links between chains which keeps the structure rigid with a high mp
Why do simple molecular(covalent) substances have low melting and boiling points? Eg. Water
There are only weak intermolecular forces between molecules which are easily overcome
Give two examples of an ionic compound
Copper oxide
Magnesium oxide
Name 3 giant covalent structures
Graphite
Diamond
Silicone dioxide
Explain why potassium oxide has a high melting point?
Strong electrostatic bonds between positive and negative ions require a lot of energy to overcome
Explain why zinc has a high melting point
Strong metallic bonds between positive ions and negative electrons require a lot of energy to overcome
Explain why ammonia and carbon dioxide have low boiling points
These covalent molecules have weak intermolecular forces- so little energy is needed to overcome them
Explain why the 3 giant structures have high melting points
These have strong covalent bonds which need a lot of energy to overcome
Which of diamond and graphite conduct electricity and why?
Graphite- it only has 3 bonds per carbon atom which means it has free electrons that can carry charge
Name 3 giant covalent structures
Graphite
Diamond
Silicone dioxide
Explain why potassium oxide has a high melting point?
Strong electrostatic bonds between positive and negative ions require a lot of energy to overcome
Explain why zinc has a high melting point
Strong metallic bonds between positive ions and negative electrons require a lot of energy to overcome
Explain why ammonia and carbon dioxide have low boiling points
These covalent molecules have weak intermolecular forces- so little energy is needed to overcome them
Explain why the 3 giant structures have high melting points
These have strong covalent bonds which need a lot of energy to overcome
Which of diamond and graphite conduct electricity and why?
Graphite- it only has 3 bonds per carbon atom which means it has free electrons that can carry charge
