Let's examine each of the possible answers and determine whether they are right or wrong. As each possibillity is discussed, also refer to the graphic shown below. The graphic shown below illustrates the diatomic (two atom) molecule HF.
A. Chemical Structure: A chemical structure is a structure that is composed of atoms held together by one or more chemical bonds. Look at the graphic shown below. Notice that the diatomic molecule HF is composed of two atoms held together by a single bond. Therefore, a compound with two atoms does have a chemical structure.
B. Bond Length: The bond length of a molecule is the average distance between the nuclei of two atoms that are bonded together. In the example shown in the graphic below, the bond length between the H atom and the F atom is about 92 pm. The bond length between atoms varies depending on the type of bond and the identity of the atoms. Therefore, a compound with two atoms does have a bond length.
C. Chemical Bond: A chemical bond is an arrangement of electrons between two atoms that holds the atoms together. The atoms in the diatomic molecule HF are held together by a single covalent bond, in which the H and F atoms share a pair of electrons. All compounds are held together by bonds. Therefore, a compound with two atoms does have a chemical bond.
D. Bond Angle: A bond angle is the angle formed by two different bonds on the same atom. Look again at the graphic shown below. Notice that both atoms in the HF molecule are attached to the same bond. In order for a molecule to have a bond angle, it must contain at least three atoms. For example, the bond angle in the three atom molecule ~CO_2 would be 180 degrees. Therefore, a compound with two atoms does NOT have a bond angle.