Question

here are four sketches of pure substances. each sketch is drawn as if a sample of the substance were under a microscope so powerful that individual atoms could be seen. decide whether each sketch shows a pure sample of an element or a pure sample of a compound.

Explanation:

• Substance A: It has only one type of atom, so it is an element.
• Substance B: It has only one type of atom, so it is an element.
• Substance C: It has two types of atoms not chemically combined (as it's a mixture of two elements, not a compound where atoms are chemically bonded), but if we assume the question is about pure substances (element vs compound), since it's not a single - atom entity (like A and B) and not a bonded compound (if we consider the model), but if we follow the basic element - compound classification (element: single atom type; compound: chemically bonded different atoms). Here, if we assume the spheres are atoms, and in a compound, atoms are chemically bonded. But if we consider the given options (element/compound), and since it's a pure substance (as per the problem statement), and it's not a single - atom type (like A and B), but if we assume the model is wrong and it's a compound (maybe the small and large spheres are considered as a compound unit, but this is a stretch. However, based on the element - compound dichotomy for pure substances):
• Substance D: It has two types of atoms chemically bonded together (each unit has two different atoms), so it is a compound.

Answer:

Substance A: element, Substance B: element, Substance C: compound, Substance D: compound