Here we have the rules for writing ionic compounds. Now, step one, we write the ions involved in the compound from the provided name. Step 2, you use these ions to write the formula of the ionic compound. So if we take a look here, we have aluminum nitride and barium phosphate.
All right, So we're going to say aluminum is in Group 3A. Because of that, its charge is Al3+ or three plus. That's why you write it as Al3+ nitride. I'd would mean that it is a nonmetal and it had its ending change to I'd Nitrogen is in Group 5A so its charge is N3-. Now if you don't quite remember the charges associated with the different groups of the periodic table, make sure you go back and take a look at my videos on the periodic table charges. OK, that'll help you see all the elements of the periodic table and what are the common types of charges based on the location of the element.
Now for this first one, when numbers and charges are the same, so here the numbers are three and three. OK. So the numbers are three and three. They cancel out to combine the elements. So since they both have three in their charges, they just cancel out. So aluminum nitride will be AlN. Now barium phosphate. Barium is in Group 2A, so its charge is Ba2+. Phosphate is one of our polyatomic ions. It's one of our common Tetra oxides. Its formula is PO43-.
Now when the numbers and charges are different, here this is 2 and this is 3, then they Criss cross. They Criss cross to combine the elements. So what I mean by crisscross is that the two from here would come here and the three from here would come here. That would give me. If we look, it would give me Ba3. The three came down here. Now this two is for the entire polyatomic ion for both phosphorus and oxygen. So because it's for both of them, I have to put it in parentheses PO4)2. So that would represent barium phosphate.
These are the things you must do when given the name of an ionic compound. Write out its ions and then look to see are the numbers and the charges the same? If so, they cancel out. Are they different? If so, crisscross them. Now, doing this crisscrossing motion, we don't have to worry about crisscrossing the charges, so you're only crisscrossing the numbers. Doing this type of action takes care of the charges on their own, so just ignore them. OK, so these would be our two formulas for these ionic compounds.
Now that we've gotten down the basics, we'll move on to some problems input to what we just learned into practice.
