Final answer:
It is false that an IDE suffix only indicates a monatomic anion; polyatomic anions can also have the suffix -ide, despite many having -ate or -ite endings.
Step-by-step explanation:
The claim that an IDE suffix usually indicates an element has become an anion and not a polyatomic ion is False. Anions formed by a single element gaining electrons indeed take the -ide suffix such as fluoride (F⁻) and oxide (O²⁻). However, there are also many polyatomic anions with names ending in -ide, such as hydroxide (OH⁻) and cyanide (CN⁻). Most polyatomic anions are named with the endings -ate or -ite, depending on their oxygen content, but this does not exclude the possibility of polyatomic anions with -ide endings.
In chemistry, the ending -ide is commonly used to indicate that an element has become an anion, not a polyatomic ion. This is because anions are formed by the addition of one or more electrons to the outer shell of an atom, whereas polyatomic ions contain more than one type of atom. An example of an anion is the fluoride ion, F¯, and an example of a polyatomic ion is the nitrate ion, NO3¯.