Which of the following compounds contains both ionic bonds and covalent bonds within its overall structure?

Introduction / Context:
This inorganic chemistry question focuses on recognising compounds that contain more than one type of chemical bond. Many ionic compounds that include polyatomic ions have ionic bonding between ions and covalent bonding inside the polyatomic ion itself. Being able to identify both ionic and covalent bonds in a single formula helps learners understand structures of salts such as sodium nitrate, calcium sulphate, and ammonium chloride, all of which combine these bonding types.

Given Data / Assumptions:
- The compounds listed are sodium nitrate (NaNO3), calcium sulphate (CaSO4), and ammonium chloride (NH4Cl).
- Each compound contains at least one polyatomic ion and a metal or cationic group.
- We assume typical valence structures where polyatomic ions are held together by covalent bonds and combine ionically with counter ions.

Concept / Approach:
An ionic bond forms between positively charged cations and negatively charged anions. Covalent bonds form when atoms share electron pairs, as in molecules and polyatomic ions. In compounds like NaNO3, CaSO4, and NH4Cl, there is an ionic bond between the metal cation (or ammonium cation) and the polyatomic anion or monatomic anion. Inside many of these ions, such as nitrate (NO3 minus) and sulphate (SO4 2 minus), the nonmetal atoms are linked by covalent bonds. Similarly, the N H bonds inside the ammonium ion (NH4 plus) are covalent. By analysing the ions present, we can see that all three compounds combine ionic and covalent bonding.

Step-by-Step Solution:
Step 1: Consider sodium nitrate, NaNO3. Sodium exists as Na plus and nitrate as NO3 minus. The attraction between Na plus and NO3 minus is ionic.
Step 2: Within the nitrate ion NO3 minus, nitrogen and oxygen atoms are bonded through shared electrons, forming covalent N O bonds.
Step 3: Consider calcium sulphate, CaSO4. Calcium exists as Ca2 plus and the sulphate ion is SO4 2 minus. The electrostatic attraction between Ca2 plus and SO4 2 minus is ionic.
Step 4: Inside the sulphate ion SO4 2 minus, sulphur and oxygen atoms are connected by covalent bonds.
Step 5: Consider ammonium chloride, NH4Cl. The ammonium ion NH4 plus is bonded ionically to chloride ion Cl minus.
Step 6: Within NH4 plus, nitrogen is covalently bonded to four hydrogen atoms through N H single bonds.
Step 7: Because each compound contains ionic interactions between ions and covalent bonds within its polyatomic ion or cation, all of them contain both types of bonding.

Verification / Alternative check:
Most inorganic textbooks illustrate the structures of nitrate and sulphate as polyatomic ions where atoms are connected by lines representing covalent bonds. The formulas NaNO3 and CaSO4 are always discussed as ionic salts composed of these ions. Similarly, ammonium salts such as NH4Cl are presented as containing the covalently bonded NH4 plus ion paired with an anion. Therefore, reference structures support the idea that all three substances have both ionic and covalent bonding, confirming that All of the above is the correct answer.

Why Other Options Are Wrong:
- Sodium nitrate (NaNO3): On its own, this option is correct in containing both bond types, but choosing only this compound ignores the fact that the others also fit the description.

Why Other Options Are Wrong (continued):
- Calcium sulphate (CaSO4): This compound also has ionic bonding between Ca2 plus and SO4 2 minus and covalent bonding within SO4 2 minus, so it is not unique.
- Ammonium chloride (NH4Cl): This also contains ionic bonding between NH4 plus and Cl minus and covalent N H bonds inside NH4 plus, so it is not the only correct choice.

Common Pitfalls:
Students sometimes assume that a compound is either ionic or covalent but cannot be both. This is a misconception because many salts with polyatomic ions have a combination of bond types. Another mistake is to focus only on the metal nonmetal nature of the formula and overlook the internal structure of the polyatomic ion. To avoid such errors, always break complex formulas into ions and examine the bonding inside each ion as well as the bonds between ions.

Final Answer:
All of the above compounds contain both ionic bonds between ions and covalent bonds within their polyatomic species.