Ions

[Zaids37]

Are you expected to know that a given certain ion is "+1" or "+2" if the passage does not provide you with what type of ion it is? This is in particular to passage 5 of gen chem for TPRH Science work book. The passage talked about ions of certain elements but did not proceed to say anything like "cation" or "anion"...just ions.

The problem is one question asked if they added 1 electron to each of the ions mentioned what would be the result:
A) all negatively charged
B) all paramagnetic
C) all diamagnetic
D) all radio active

The answer is B. I'm confused because this makes sense for certain ions (Na+, Li+, K+)...but for others it did not unless I knew the oxidation state of the ion which was not mentioned in the passage. Is there a list with common ions or something that I should memorize? I had no idea a barium or strontium ion would be +2

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[Cawolf]

Yes - at least the +1, +2, +3, -1, -2, and -3 ions are pretty standard to know.

Look at this and see if you see the trend for yourself. . .

Groups 4 - 14 are not as straightforward.

http://www.sciencegeek.net/tables/PT_ions.pdf

 

[Zaids37]

Yes - at least the +1, +2, +3, -1, -2, and -3 ions are pretty standard to know.

Look at this and see if you see the trend for yourself. . .

Groups 4 - 14 are not as straightforward.

http://www.sciencegeek.net/tables/PT_ions.pdf

Ok I see the trend now...I had a feeling it was like that after a more thorough analysis, just was confused as to why the s orbital ones (groups I and II) were positive and the ones near the end are negative but I'll just memorize them that way.

Is it advisable to memorize the oxidation states on all polyatomic ions as well?? In one of chad's video's he referenced this but I'm not sure if this is what he was referring to memorizing.

 

[2Pints]

Ok I see the trend now...I had a feeling it was like that after a more thorough analysis, just was confused as to why the s orbital ones (groups I and II) were positive and the ones near the end are negative but I'll just memorize them that way.

Is it advisable to memorize the oxidation states on all polyatomic ions as well?? In one of chad's video's he referenced this but I'm not sure if this is what he was referring to memorizing.

If by oxidation state on the polyatomic ion you mean the charge of the polyatomic ion - yes I would memorize the charges for common polyatomic ions.

I wouldn't memorize the oxidation state of each element within a polyatomic ion. That's easy enough to figure out when you know the charge.

 

[Cawolf]

Ok I see the trend now...I had a feeling it was like that after a more thorough analysis, just was confused as to why the s orbital ones (groups I and II) were positive and the ones near the end are negative but I'll just memorize them that way.

It is due to the number of valence electrons and how easy it is for the element to gain a full octet. The group 1 elements give up an electron easily to have a full octet while the halogens gain one electron. This is a common trend.

 

[Zaids37]

If by oxidation state on the polyatomic ion you mean the charge of the polyatomic ion - yes I would memorize the charges for common polyatomic ions.

I wouldn't memorize the oxidation state of each element within a polyatomic ion. That's easy enough to figure out when you know the charge.

Which ones would be common? Cause thats a loooong list lol

It is due to the number of valence electrons and how easy it is for the element to gain a full octet. The group 1 elements give up an electron easily to have a full octet while the halogens gain one electron. This is a common trend.

And thanks Cawolf! that makes it much easier to understand!

 

[2Pints]

@Zaids37 start with the ones that form a patterns and memorize those in blocks. I'm not big on memorizing things but having a good familiarity with the polyatomic ions is important for weeding out obviously wrong problems and preventing simple mistakes. For instance if you didn't know the sulfate ion had a -2 charge then HSO4 might look correct when it should be H2SO4. I saw you are using Chads videos which I found helpful reviewing material I haven't touched in 8 years (ugh Physics).

I use YouTube a lot too. Just search for memorize common ions. There are tons of videos that are only a few minutes long and might give you grouping tricks and things like that.

Besides YouTube there's a simulation lab I've used a few times at phet.colorado.edu it's very very basic but if you don't have a good grasp on the basics this test will be harsh. Play around with building molecules or titrations. It's nice having the visual effect.

One thing I would do is make or search online for a template of the ions without their charges. Or the ion names and you have write the formula. Print several copies and just practice filling in the blanks. Every day.