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Topic: Find the formula of the "maximum oxide"  (Read 192 times)

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Offline INeedSerotonin

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Find the formula of the "maximum oxide"
« on: July 12, 2019, 11:19:53 AM »
Hello

I want to learn how to solve this exercise. Could you please help me?

Here it goes: 1) A "maximum oxide" is an oxide that contains the element in its maximum oxidation state (from +1 up to +9). Find the formula of the following "maximum oxides": a) V; b) Ge; c) Mn; d) Zr; e) Cr.

Could please tell me how to solve at least (a), so I can try to solve the next ones by myself?

The answers are these:

a) V2O5
b) GeO2
c) Mn2O7
d) ZrO2
e) CrO3

Offline Corribus

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Re: Find the formula of the "maximum oxide"
« Reply #1 on: July 12, 2019, 11:28:29 AM »
Well the first step is to identify what the maximum oxidation state is of the positively charged elements in each oxide. This is for the most part just something you have to memorize, or look up. So (a) is vanadium. What is the max oxidation state of vanadium?
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline INeedSerotonin

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Re: Find the formula of the "maximum oxide"
« Reply #2 on: July 12, 2019, 11:33:15 AM »
Well the first step is to identify what the maximum oxidation state is of the positively charged elements in each oxide. This is for the most part just something you have to memorize, or look up. So (a) is vanadium. What is the max oxidation state of vanadium?

Hello! Thank you for your answer. This is exactly the problem. If it were elements from the A families instead of the B, then I could easily solve it.

Vanadium's configuration is, for example, [Ar] 4s2 3d3. So it has 2 electrons on the valence shell, and it means it can lose its two last electrons to become stable like a noble gas. But where does +5 come from? I suppose that is the answer for what you have asked me, for the answer of the exercise is V2O5. O is -2, so V must be +5.

Is there some way to discover these values? Or is the only way by memorising?

edit: I have just noticed how it needs to lose 5 electrons to become stable. Sorry, I must have attention deficit. Is this the answer?

EDIT 2: YESSSS. Thank you very much. I just needed someone to guide my thoughts. I finally have learned it! It seems like it was exactly that: the metal must oxide and lose its electrons orbital by orbital from +1 to +9 to become exactly like a noble gas. Doing this and assigning the number of oxygens led me to the answers successfully!
« Last Edit: July 12, 2019, 12:05:06 PM by INeedSerotonin »

Offline Corribus

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Re: Find the formula of the "maximum oxide"
« Reply #3 on: July 12, 2019, 12:00:20 PM »
More or less- the highest oxidation state possible is usually the case where the metal atom loses all the electrons in its valence shell to have a noble gas configuration. So, in the most elementary treatment, vanadium can lose 3 d electrons and 2 s electrons to become like an argon atom. Therefore its highest oxidation state is +5.

Transition metals are a little strange with the way their orbitals get filled so this isn't always a rigorously correct way to view things, but the approach will usually get you the right answer to this kind of problem.

That in mind, can you now rationalize the other answers based on where those metals are in the periodic table?
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline INeedSerotonin

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Re: Find the formula of the "maximum oxide"
« Reply #4 on: July 12, 2019, 12:04:55 PM »
Yes! Thank you! I've found the answers. It all makes sense to me now!  ;) ;D

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