Binary Compounds Type II

This post is a continuation of scrambling your brains with naming compounds. So far we know that binary ionic compounds Type I contain metals that always give the same cation. For example, Lithium always forms the Li ¹⁺, Magnesium forms the Mg ²⁺ , and Aluminum always forms the Al ³⁺. However, there are many metals that can form more then one type of cation. For example, Iron can be Fe ²⁺ or Fe ³⁺ and Chromium can be Cr ⁺², Cr ⁺³, or Cr ⁺⁶ . Because those metals can have different charges, we need to identify, which cation is present in compounds containing metals that can form more than one type of cation. Therefore, chemists used a Roman numeral to specify the charge on the cation. The rules for naming those compounds are called binary ionic Type II compounds and they are very similar to Type I.

Rules

1. The cation is always named first, and the anion second.

2. The cation is name after the element.

3. The anion is name by taking the first part of the element name and adding –ide.

4. Use a Roman number to specify the charge on the cation.

Examples

Compounds of iron and chlorine

Fe Cl, where Fe can have charge +2 or +3 and Cl is always -1.

Fe ^? Cl ^-1  to balance them to 0, we need to have on both sides  Fe ⁺² and Cl ^-2 or Fe ⁺³ and Cl ^-3  so what do we need for both sides?

If we want to have charge +2 for iron we need to have charge -2 for chlorine, the compounds will look like that FeCl₂; let’s check if the elements are balanced to 0.

+2     -1   charges

Fe₁Cl₂; Fe +2 times 1(single Fe has one atom you don’t need to write the 1)= positive two, and Cl -1 times 2 = negative two. The name of the compounds is iron (II) chloride

if we want to have charge +3 for iron we need to have charge -3 for chlorine, the compounds will look like that FeCl₃; let’s check it the elements are balanced to 0.

+3     -1

Fe Cl₃ ; Fe +3 times 1= positive 3 and Cl -1 times 3= negative 3. The name of the compounds is iron (III) chloride.

Well naming compounds may seem difficult but practicing problems will make you a master.