Fruitcake05 said:
Hey guys, im new to chem, just wanna make sure
1. Refering to bonding, why are metals better conductors of electricity then non metals?
Is it because of the valencies, metals have a positive charge whilst non metals are negative?
2. Will I need to know about haloalkanes, alkenes, alkynes etc. for the prelim course as well as the HSC?
3. Any good study notes around eg like a table with common bonds etc.
4. In the HSC exam what would be the average mark, and the highest mark and what things would I have to do now to try and achieve it?
5. Best textbook around?
Thanks. Help is greatly appreciated.
1) Metals like iron are transitional and have valency of 2 or 3, usually. This means iron could gain 6 electrons, but it is FAR FAR easier for it to simply give away two of its own to become neutral. Something like oxygen however has valence 6 and needs only 2 more electrons to fill its outer shell. As such, oxygen will react with things like iron and strip 2 electrons away. This means that oxygen is gaining electrons (becoming negative) and iron is loosing electrons (becoming positive). So if you were to break iron oxide into its constituent ions you would get positive iron and negative oxygen.
As to why irons are more reactive - simple answer is, they aren't. You'll find that some of the non-metals are quite reactiver (oxygen and hydrogen for example). By the same token metals like sodium are extremely reactive. On the other had metals like gold or non-metal noble gases like argon are extremely unreactive. In fact since argon is noble and has a full outer electron shell, it is an inert gas. It can still react under special cirumstances such as if it is a plasma (ionised gas).
EDIT: Ah, you said "Why are metals better conductors" that is slightly different.
As above we noted that metals generally LOSE electrons, yes? Well, electrical current occurs when there is a flow of electrons. Now, metals are actually made of a lattice structure. Within this structure there are things called "electron holes" and electrons migrate en mass from one hole to another, towards the other end of the circuit. You probably know about covalent bonds. Well, non-metals like oxygen tend to form covalent bonds in which there are no such electron holes. Furthermore, covalent molecules don't always form a lattice.
Now, non-metals like carbon can conduct sometimes. When carbon is in the form of graphite or fullerene (nanotubes, buckbyballs), it forms an orderly structure which facilitates the movement of electrons.
2) Dunno about prelim. I didn't pay attention in class then. But in HSC you will be THOROUGHLY grounded in alkanes and alkenes. Alkynes are not part of the syllabus.
3) You'll pick up a lot of that stuff by osmosis. However you certainly should make your own study notes which correspond to the syllabus dotpoints, at least for year 12.
4) Don't worry about that kind of stuff. Just make sure you take the course seriously and have good study habits by the time you hit year 12 (you don't necessarily need them now).
5) Conquering Chemistry is the best by my experience. Macquarie revision guide supplements it very nicely.
