To determine which of the given options is a polyatomic ion, let’s first understand what a polyatomic ion is.
A polyatomic ion is a charged particle which has two or more atoms bonded together, with an overall positive or negative charge. These atoms can be of the same element or different elements.
Now, let's analyze each of the given options:
A. [tex]\( N_2 \)[/tex] – This is a molecule of nitrogen, a diatomic molecule with no charge. It does not qualify as a polyatomic ion.
B. HCl – This is a molecule of hydrochloric acid in its molecular form, which consists of hydrogen and chlorine. It does not qualify as a polyatomic ion as it is not an ion, but a simple molecular compound.
C. [tex]\( S^{2-} \)[/tex] – This is a sulfide ion, which is a monatomic ion (it contains only one atom of sulfur with a charge of 2-). Therefore, it is not a polyatomic ion.
D. [tex]\( PO_4^{3-} \)[/tex] – This is a phosphate ion which consists of one phosphorus atom and four oxygen atoms, bonded together and carrying a charge of 3-. This fits the definition of a polyatomic ion as it contains more than one atom and has an overall charge.
Therefore, the correct answer is:
D. [tex]\( PO_4^{3-} \)[/tex]
