Names of polyatomic ions usually end in -ite or -ate and names of ionic compounds end in the name of the anion in the compound. If the name ends in -ate how can you tell if it's a polyatomic ion or an ionic compound with a polyatomic ion as its anion other than memorizing it? Thanks. Sorry if it's a stupid question.

If it is an ionic compound, then in front of the name of the anion, the name of the cation is mentioned.

 

SO4(2-) : Sulfate

 

Na2SO4 : Sodium sulfate (here the cation is Na(+)).

 

You need to memorize the names of anions (sulfate, nitrate, sulfile, chlorate, ....). You also need to memorize the names of cations (sodium, potassium, ammonium, ....). When you see a combination of such names, then it is an ionic compound. When you only see the name of the anion, then it is an ion.

 

There also are compounds like SO3, ClO2, NO2. These of course are not called sulfite, chlorite and nitrite, these are neutral oxides.

Also, typically speaking there are very few polyatomic cations. (Ammonium and uranyl are the few that come to mind). However, you'll know it's a polyatomic cation because the name will not be the that of an element.

Also, typically speaking there are very few polyatomic cations. (Ammonium and uranyl are the few that come to mind). However, you'll know it's a polyatomic cation because the name will not be the that of an element.

 

Though, be careful with ones like Sulfates and Silicates, which are polyatomic, but sound like they could be monoatomic (note the 'ate' instead of the 'ide'

Also, typically speaking there are very few polyatomic cations. (Ammonium and uranyl are the few that come to mind). However, you'll know it's a polyatomic cation because the name will not be the that of an element.

You'd better say, there are very few common polyatomic cationic species, which are used on high schools. In reality there are many more, even quite common ones:

 

vanadyl: VO(2+)

hydrazinium: NH2NH3(+) and (+)NH3NH3(+)

all kinds of substituted ammonium ions with 1,2,3 or even 4 substituted H's.

nitrosyl: NO(+)

nitryl: NO2(+)

...

Though, be careful with ones like Sulfates and Silicates, which are polyatomic, but sound like they could be monoatomic (note the 'ate' instead of the 'ide'

Sulfates and Silicates aren't cations, however.

 

@Woelen: Very true. I should have put that caveat in there.

Sulfates and Silicates aren't cations' date=' however.

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Of course not... more of a response to the OP.

That simplifies some stuff. Thaks.