Discrete diatomic molecules

[luken93]

I've got a question from StudyOn, but if someone could clarify the answers with me

Which of the following substances contain discreet diatomic molecules
a) Magensium Oxide (No because it has 2 elements)
b) Iodine (Yes because it has a single bond)
c) Aluminium (No because it is a metal)
d) Neon (No because it is a noble gas = full outer shell)
e) Phosphorus (I said yes because it could have a triple bond but the answer is no? I think there is something i don't know)
f) Carbon Dioxide (3 atoms in the molecule)

Thanks

[Edmund]

No it can't be phosphorus because it is P₄ naturally. P₄ is the most common form (white phosphorus I think). You will learn this in inorganic chemistry.

[luken93]

No it can't be phosphorus because it is P₄ naturally. P₄ is the most common form (white phosphorus I think). You will learn this in inorganic chemistry.

so there is no way of knowing it when doing covalent bonds until you get to inorganic chemistry/

[Edmund]

Well yeah. You should be able to know the structures of the rest though... I₂ is quite common I think. You might not have seen phosphorus, but if you google it, you will find that it has a tetrahedral shape (there are other structures too, we call them allotropes, something like isomers)

[luken93]

Well yeah. You should be able to know the structures of the rest though... I₂ is quite common I think. You might not have seen phosphorus, but if you google it, you will find that it has a tetrahedral shape (there are other structures too, we call them allotropes, something like isomers)

yeh dont think i'm up to that yet haha. only starting ionic, metallic, covalent bonding, so i'm guessing its a little way off yet

[Mao]

No it can't be phosphorus because it is P₄ naturally. P₄ is the most common form (white phosphorus I think). You will learn this in inorganic chemistry.

That's not a valid reason for why P can't form discrete diatomic molecules.

P₂ does exist, and luken93 is quite right in saying that it has a triple bond. However, with his current knowledge of Chemistry, he wouldn't have made the jump that P4 is much more stable than P2.

luken93: take a read here http://en.wikipedia.org/wiki/Diphosphorus if you feel like it, the nature of the P2 triple bond is very different to the N2 triple bond (prior is reactive, latter is stable). P2 is not naturally found as it spontaneously converts to P4 or other more stable allotropes of phosphorous.

[luken93]

No it can't be phosphorus because it is P₄ naturally. P₄ is the most common form (white phosphorus I think). You will learn this in inorganic chemistry.

That's not a valid reason for why P can't form discrete diatomic molecules.

P₂ does exist, and luken93 is quite right in saying that it has a triple bond. However, with his current knowledge of Chemistry, he wouldn't have made the jump that P4 is much more stable than P2.

luken93: take a read here http://en.wikipedia.org/wiki/Diphosphorus if you feel like it, the nature of the P2 triple bond is very different to the N2 triple bond (prior is reactive, latter is stable). P2 is not naturally found as it spontaneously converts to P4 or other more stable allotropes of phosphorous.

ok thanks heaps mao, as you said i have only started on covalent and i just thought that because N₂ is a triple bond, then P₂ could be diatomic as well.
So can it be diatomic but it just prefers to be P₄, therefore it's not classed as diatomic?

[Mao]

diatomic: di- means two

And yes, you are correct. It can be diatomic but it prefers to be P4. http://en.wikipedia.org/wiki/File:White_phosphrous_molecule.jpg

[It actually prefers to be a different structure - http://en.wikipedia.org/wiki/File:Schwarzer_Phosphor.svg, but the conditions required are a bit ridiculous]

[luken93]

diatomic: di- means two

And yes, you are correct. It can be diatomic but it prefers to be P4. http://en.wikipedia.org/wiki/File:White_phosphrous_molecule.jpg

[It actually prefers to be a different structure - http://en.wikipedia.org/wiki/File:Schwarzer_Phosphor.svg, but the conditions required are a bit ridiculous]

fair enough then, I will attack that when I get up to it