Which of the following compounds contains a polyatomic ion?
a. NH3
b. HCI
c. NaOH
d. MgBr2
e. Ca3N₂
The Correct Answer and Explanation is :
The correct answer is c. NaOH (Sodium hydroxide).
Explanation:
To determine which compound contains a polyatomic ion, we need to understand what a polyatomic ion is. A polyatomic ion is a charged ion composed of two or more atoms covalently bonded, acting as a single unit. These ions can be either positively charged (cations) or negatively charged (anions). Common examples include sulfate (SO₄²⁻), ammonium (NH₄⁺), and hydroxide (OH⁻).
Now, let’s examine each compound:
- NH₃ (Ammonia): This is a neutral molecule, not an ion. It does not contain a polyatomic ion. It consists of one nitrogen atom and three hydrogen atoms, all covalently bonded. Since it does not have a charge, it is not considered an ion and does not contain a polyatomic ion.
- HCl (Hydrochloric acid): This compound consists of hydrogen and chlorine. It forms a simple ionic bond between H⁺ and Cl⁻ ions when dissolved in water, but these ions are individual atoms, not polyatomic ions. So, it does not contain a polyatomic ion.
- NaOH (Sodium hydroxide): Sodium hydroxide consists of the sodium ion (Na⁺) and the hydroxide ion (OH⁻). The hydroxide ion (OH⁻) is a polyatomic ion composed of oxygen and hydrogen atoms, bonded together and carrying a negative charge. Therefore, NaOH contains a polyatomic ion.
- MgBr₂ (Magnesium bromide): This compound contains magnesium ions (Mg²⁺) and bromide ions (Br⁻). Both ions are monatomic (consisting of single atoms), so this compound does not contain a polyatomic ion.
- Ca₃N₂ (Calcium nitride): This compound consists of calcium ions (Ca²⁺) and nitride ions (N³⁻). The nitride ion is a monatomic ion, so this compound does not contain a polyatomic ion.
Thus, the only compound in the list that contains a polyatomic ion is NaOH.