e.g. Na + SO4 2- -> Na2SO4
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
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. =)
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.
CaF2
Formula: AgI
CaO.
See link below
Barium Fluoride is BaF2.
CaF2
When KOH is placed in water, it ionizes to K+ and OH-, so the polyatomic ion is the OH- (hydroxyl anion).
Formula: AgI
See link below
CaO.
Formula: Li2O
Formula: BCl3
You use the prefix of the words to write the formula for a covalent compound, example "di-" is the prefix and it is 2.
Which sport is better, basketball or baseball
Pb3(PO4)2
Barium Fluoride is BaF2.
It is written as Na2CO3. It is a base compound.