What do we need to know about oxidation states?

[Jay0689]

What kind of rules do you memorize to get these oxidation state questions right?

Destroyer GC #36.

An unknown compound needed to be identified. Studies revealed that it reacted with oxygen and flourine to yield Y2O3 and YF3. Which element listed below could be element Y?

As, C, Mg, Ar, Hg.

As is correct. The answer says that Arsenic is a semi-metal (metalloid) which can carry valences of +3,-3, or +5. Y is +3 in both compounds so As is the answer.

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[spoog74]

What kind of rules do you memorize to get these oxidation state questions right?

Destroyer GC #36.

An unknown compound needed to be identified. Studies revealed that it reacted with oxygen and flourine to yield Y2O3 and YF3. Which element listed below could be element Y?

As, C, Mg, Ar, Hg.

As is correct. The answer says that Arsenic is a semi-metal (metalloid) which can carry valences of +3,-3, or +5. Y is +3 in both compounds so As is the answer.

i dont think this is an oxidation state question ....The question is basically testing your knowledge of the type of ions that elements make. If you look in the periodic table, As is under the 5th group which means it makes 3+, 3- ions. The other elements such as Mg makes 2+, and so on.... Its just a general trend that you need to be familiar with

 

[Jay0689]

Ok thanks spoog.

Why do group 5 elements make 3+ ions? That would not give them 8 valence electrons.

Also, should you know that Hg does not make the 3- ion? (Is it necessary to know the possible oxidation states of the transition metals?)

Can you predict the ion charges for the "other metals" and metalloids based on group # like you can for everything else besides the transition metals?

 

[spoog74]

Ok thanks spoog.

Why do group 5 elements make 3+ ions? That would not give them 8 valence electrons.

Also, should you know that Hg does not make the 3- ion? (Is it necessary to know the possible oxidation states of the transition metals?)

Can you predict the ion charges for the "other metals" and metalloids based on group # like you can for everything else besides the transition metals?

Yeah, the second group metals almost always make 2+ ions, and 1st group metals make +1 ions. The 7th group non metals make -1 ions, 6th group make -2 ions.

Hg never comes up so i wouldnt worry about it. Be familiar with ions such as Iron, Aluminum ( the ones that come up the most)

 

[Vsno123]

yeah, I don't understand this question either. I know As can be -3, but why can it be +3? I never heard of rules for elements in group 5A.