Question

given the simple representations for atoms of two elements:
○ = an atom of an element
● = an atom of a different element
which particle diagram represents molecules of only one compound in the gaseous phase?
a.
b.
c.
d.

Explanation:

Step1: Recall the definition of a compound

A compound is a substance formed when two or more different elements chemically combine in a fixed ratio.

Step2: Analyze Option A

In Option A, all the molecules are made up of only one type of atom. So, these are elements (not compounds).

Step3: Analyze Option B

In Option B, there are two types of molecules (one with only white - circle atoms and the other with only black - circle atoms). These are two different elements, not a compound.

Step4: Analyze Option C

In Option C, there are two types of molecules. One type of molecule has a fixed ratio of white and black atoms (compound - like), but there is also another type of molecule (with a different combination). So, it is a mixture.

Step5: Analyze Option D

In Option D, all the molecules are made up of the same combination of two different types of atoms (white and black) in a fixed ratio. This represents molecules of only one compound. Also, the particles are far apart (gaseous phase as per the general representation of gas in particle diagrams where particles have more space between them compared to solids and liquids).

Answer:

D.