Flashcards in 2.1 Structure and Bonding Deck (29)
What is a polymer?
Polymers are very large molecules and
each polymer molecule is a long chain of mainly carbon atoms.
How do metals conduct heat energy?
Because they have delocalised electrons which are free to move and can carry energy with them.
Why are metals usually cool to touch?
Because they conduct the energy given out away from your hand, which then cools down.
Why are pans usually made from metals?
Because they conduct the heat from the flame or energy source to the content of the pan.
How is the structure of metals held together and why do metals have such high melting and boiling points?
They are held together by the electrostatic attraction between the positive metal ions and the negative delocalised electrons. This attraction is strong, so metals have high melting and boiling points.
What is the structure of metals?
The metal atoms are packed close together in a regular metallic structure.
What happens when the outer shell electrons from each atom become free to move about the metal?
A giant structure (lattice) of positive metal ions surrounded by delocalised electrons is left.
Why are metals easy to shape?
Because the layers of metal ions can slide over each other while keeping the strong attraction between the positive metal ions and the delocalised electrons.
Why do atoms with just a few electrons try to lose them? (Hint: Group 1)
Answer: They do this so that they can try to get a more stable outer shell by losing enough that the outer shell is full.
Explanation: Group 1 electrons only have one electron on the outer shell. Losing that would make them more stable; overall it would now have a single positive charge. These charged particles are called ions.
Who do atoms just short of the noble gas structure try to gain electrons?
Because they want enough electrons for a full outer shell, to make it more stable.
What is a halogen?
An element in group 7 e.g. Fluorine, chlorine or iodine.
These react with metals to form ionic compounds containing halide ions.
Name two examples of ionic compounds.
Sodium chloride (NaCl) and magnesium oxide (MgO).
What is a halide ion?
A negatively charged ion formed from one of the group 7 elements.
Why is the noble gas electron structure very stable?
The noble gases have a full outer shell so they don't react as there is no opportunity for them to do this. They have no space on their outer shell.
What are the properties of diamond?
Very Strong due to the intermolecular forces of the covalent bond. High melting points and boiling points. Doesn't conduct electricity due to no delocalised electrons- each carbon has 4 bonds.
What are the properties of graphite?
High melting and boiling points. Can conduct electricity due to the delocalised electrons- each carbon has 3 covalent bonds. Soft because the layers are free to slide.
Properties of silicon dioxide.
Each silicon atom is covalently bonded to four oxygen atoms- this makes the structure very hard, so it has high melting and boiling points. It doesn't have any delocalised electrons due to the covalent bonds creating full outer shells, so it doesn't conduct.
What is a simple covalent structure?
A simple covalent structure is carbon dioxide for example; unlike the giant structure, the bonds aren't continuous. This means, simple covalent structures have weak intermolecular forces that require low energy to overcome. Therefore, they have low melting and boiling points.
What is a giant covalent bond.
A giant covalent structure with high melting and boiling points; the main ones being diamond, graphite and silicon.
Why do ionic compounds have high melting and boiling points?
Because ionic bonds are strong and require a lot of energy to break them.
How does an ionic compound form?
From a metal reacting with a non-metal.
Why do molten ionic compounds conduct electricity?
Because the charged ions are free to move.
What type of atoms are covalent molecules only made from?
How do atoms in covalent molecules gain electrons?
By sharing electrons
How many electrons does chlorine need to complete its outer shell?
What is the formula for ammonia?
How long is a nanometre?
A nanometre is one billionth of a metre.
What are some of the properties of nanoparticles?
Nanoparticles have a very large surface area compared with their volume, so they are often able to react very quickly. This makes them useful as catalysts to speed up reactions.