University:
Bradley University
Course:
CHM 100 | Fundamentals of General Chemistry
Academic year:

2023
Views:

399

Pages:

3
Author:

Gudrunecg9m

When writing names for ionic compounds, we must first determine if the metal in the compound is a transition metal. If the metal IS a transition metal, the charge of the metal must be shown as part of the name. On the periodic table shown below, any element shaded in blue is an element that must include a charge as part of its name. *Even though the metals under the staircase are not usually classified as transition metals, they form ions of >1 charge, so the rules for naming them are the same as for naming transition metals. Some metals that are in the blue region, like zinc, do only form one charge. Therefore, you may not always see their charge written as part of their name. We won’t worry about those exceptions for right now. IF NO TRANSITION METAL IS PRESENT: Simply write the name of each ion/ polyatomic ion present. The name ends in -ide of no polyatomic ion is present. Ex. CaS = calcium sulfide NaNO3 = sodium nitrate IF A TRANSITION METAL IS PRESENT: The charge on the transition metal must be included in the name. This is done by writing the charge in Roman numerals in parenthesis next to the metal.  To figure out what the charge is, simply “uncross” the number from the opposite ion (do the opposite of what you would do to write the formula)  NEVER take a subscript away from a polyatomic ion! Ex. CuCl2 = copper (II) chloride Ex. Fe2(SO4)3 = iron (III) sulfate You MUST remember to take the subscript from the ion NEXT to the metal, NOT the subscript next to the metal itself. Ex: Fe3O2 = iron (II) oxide NOT iron (III) oxide The only tricky scenario is when no subscript is present in the formula. You cannot just assume that no subscript implies a “1”. To figure out the charge on the metal, first figure out the charge on the anion by referring to the periodic table or your polyatomic ion sheet. Ex. FeO O is always 2- (from the periodic table) If oxygen is O2-, than iron must be Fe2+. So FeO = iron (II) oxide WHY? Because the charges on the metal and the anion must cancel. The reason why you don’t see the 2’s in the formula is because whenever the charges are equal but opposite, they cancel. Ex. CrP = chromium (III) phosphide Ex. AuCl = gold (I) chloride Ex. FeSO4 = iron (II) sulfate NOT iron (IV) sulfate WHY? You can’t take the 4 away from sulfate, it would just be SO and “SO” is NOT sulfate. The charge on sulfate (SO4) is 2-.