How do write the formula for a compound containing a polyatomic ion?

Answer 1

1. Write the symbol of the cation first, than the anion
2. State the combining capacity for each element over each of the ions
3. Use the 'cross over' method and reduce the numbers to the lowest ration (without changing the formula for the ion)

e.g. Na + SO4 2- -> Na2SO4

Answer 2

U just need to remember the overall charge of the polyatomic ion for example no3- that's enough

In case of ionic compound

For example magnesium ion and nitrate ion

Magnesium is 2 positive charge while nitrate ion is 1 negative charge.(in order to achieve octet structure) To form ionic compound for example it should be mg(no3)2 but not mgno3 2 that's because no3 is an ion carry overall 1negative charge it cannot be seperate as no32 because that will change the meaning therefore remeber to use () when form ionic compound when polyatomic ion is used

Answer 3

Generally, polyatomic ions all have charges, or valency electrons which act as the charges as a whole. They are considered as a whole category of compounds in chemistry which have a combined charge. You should look up list of polyatomic ions for Google, if you need to learn them. To write the formula, simply look at the charges, in which for example, Sodium hydroxide. (Sodium, Na, had +1 charge, an alkaline metal element. And Hydroxide, OH- had a -1 charge, and is a polyatomic ion). The charges must equal 0, so in this case, you can simply write Sodium Hydroxide by NaOH (since +1 -1 = 0). This works normally for all other ions as well. Note that properties of the element will also alter which polyatomic ion can bond to what type of element. Multiple polyatomic ions can bond to an element also, to form other types of compounds. Also note that the name of the element came before the polyatomic ion, which is another important thing to remember. =)

Answer 4

Make sure you are familiar with the most common polyatomic ions. Look at the locations of the elements on the Periodic Table. Atoms in the same column as each other tend to exhibit similar characteristics, including the number of electrons the elements would need to gain or lose to resemble the nearest noble gas atom.