Identifying an element

[Wai]

Okay, the question asked me to provide an example of an element that had the properties that it specified. All the others were easy, but I'm really confused about this one:

 

- Lacks metallic lustre

- Lacks ductility

- Good conductor of electricity as a solid

- Very unreactive

- Solid at room temperature

 

Here's what I think:

- Can't be a metal then

- Metalloid or non-metal then

- Good conductor? ...

- Very unreactive, noble gases? (since gold was eliminated)

- Solid? Not the noble gases then...

 

So what could this element be?

[swansont]

My guess is that you might want to chew your pencil while you ponder this.

[Wai]

Could it possibly be a typo in the textbook?

[insane_alien]

no typos but it might have been penciled in. <another big hint to follow swansonts.

[Wai]

You're not talking about carbon are you? Is it unreactive though? That's what I thought, but doesn't it form a lot of compounds?

[insane_alien]

yes, it does form an awful lot of compounds. doesn't mean that it is very reactive though. and unless you can think of another non-metal conductor that is an element i think carbon will have to be it. carbon, specifically the graphite allotrope, is usually unreactive which is why it is used in electrodes quite often.

 

it takes a bit of effort to get it to react to form hydrocarbons though which is why petrol has such a high energy density and is a good fuel.

 

EDIT> just thinking here, how much do you know about electron orbitals? if you know what a sp³ orbital is i'll explain it.

[swansont]

You're not talking about carbon are you? Is it unreactive though? That's what I thought, but doesn't it form a lot of compounds?

 

Carbon isn't all that reactive AFAIK (at least at room temp). It does form compounds, but how does it do so? Not so much on its own. If it were reactive, it wouldn't just sit there and be carbon, like in graphite or diamond. It would react. C isn't going to be as unreactive as a noble gas, but you have to take that as given, as you are looking for a solid.

[Genecks]

Graphite. lol..

 

I was talking to Doll A, and it said "semiconductor!" I was talking to Doll B, and it said, "Possibly non-metal!"

 

I dunno, 'cause the ppl don't tell me theze thingz. lolz.

[Wai]

it takes a bit of effort to get it to react to form hydrocarbons though which is why petrol has such a high energy density and is a good fuel.

 

EDIT> just thinking here, how much do you know about electron orbitals? if you know what a sp³ orbital is i'll explain it.

Yeah, I know what subshells are. So it should be carbon then.

[insane_alien]

so you should know that carbons electron arangement is 1s2 2sp^3 4

 

so its 4 sp^3 orbitals are half filled. this is the second most stable arrangement (the most stable being having them all filled) the other arrangements aren't as stable so are more likely to break down.

 

Since it has this stability, it won't react unless its forced to. the fact that its 4 possible bonds can form a fantastic array of chemicals doesn't have much to do with reacitivity.

[Genecks]

I'm still having trouble believing it's carbon, because carbon is used as a resistor and not a "good" conductor of electricity. I'm thinking it's glass.

[insane_alien]

Genecks, have you never used carbon electrodes? carbon conducts fine. well, as long as you move the current across the planes of the graphite and not perpendicularly to them. then it doesn't work. carbon nanotubes can also behave like mini(nano) wires

 

diamond and amorphous carbon will not conduct since they do not contain delocalised electrons.

 

see here: http://en.wikipedia.org/wiki/Graphite

 

Graphite (named by Abraham Gottlob Werner in 1789 from the Greek γραφειν (graphein): "to draw/write", for its use in pencils) is one of the allotropes of carbon. Unlike diamond, graphite is an electrical conductor,

[John Cuthber]

When you say "I'm thinking it's glass." do you mean glassy carbon (which is a form of graphite)?

[insane_alien]

well it sounds like genecs is thinking of normal glass but thats not an element so it doesn't meet the requirements for the question. carbon is the only non-metal room temperature conducting element thats reasonably unreactive.

[Genecks]

Right, we're looking for element.

[insane_alien]

carbon fits the criteria

 

- Lacks metallic lustre check, graphite is black

- Lacks ductility check, graphite is brittle

- Good conductor of electricity as a solid check, graphite conducts

- Very unreactive check, graphite is stable(the stablest form of carbon

- Solid at room temperature check, doesn't sublime until over 3000*C

[Wai]

I was just confused with that question because my textbook was rating reactivity as:

 

Very reactive: Caesium, fluorine etc.

Reactive: Aluminium, magnesium etc.

Unreactive: Gold etc.

Very unreactive: Helium, neon etc.

 

The question said "very unreactive", so I assumed that it would be something like a noble gas. If it just said "unreactive", then I would have looked onto carbon a little more.

[insane_alien]

well, i've never known a noble gas to conduct electricity(appart from when its ionized but thats a whole different shebang). or be solid at room temperature. so you can't use them.

 

its fine that you were a bit confused, it happens to the best of us. you got something out of this and thats the main point.

[Wai]

Apart from carbon and silicon, are there any other good conductors of electricity that are metalloids or non-metals?

[YT2095]

Antimony and Tellurium conduct quite well, I have both of these at 99.99%+ purity and they conduct quite well even on a simple DVM.

Germanium is said to conduct also, however I can`t manage to make mine conduct?

it also is very pure.

[swansont]

Si and Ge are intrinsic semiconductors, so they probably shouldn't be thought of as "good conductors"

[Nevermore]

What about silicon?

[YT2095]

Good question, I just tried this and My silicon conducts Very well, even on the Ohms setting.

[swansont]

According to this table Si is a worse conductor than Ge, and they are way at the top of the list, which is from worst-to-best (6th and 7th worst of the ones listed)

 

But, like Carbon (diamond vs graphite), the structure of Si may matter. If it's not a good crystal, or there are impurities, the conductivity may be higher.

[YT2095]

both my Si and Ge are crystaline form and >99.99% pure.

eitherway, it`s not the element he`s looking for, Si is far too reactive compared with Carbon.