Answer
PART A: Molecular element.
PART B: Molecular compound.
PART C: Atomic element.
Work Step by Step
PART A: By inspection of this space-filling model, this is a molecular element because it consists of independent molecules of only one type of element.
PART B: By inspection of this space-filling model, this is a molecular compound because it consists of independent molecules with two types of elements.
PART C: By inspection of this space-filling model, this is an atomic element because it consists of only one type of element.