Video Transcript
Which of the following statements
that compare two d-block elements is correct? (A) Vanadium is less dense than
copper and has a smaller atomic radius. (B) Vanadium is less dense than
copper but has a larger atomic radius. (C) Vanadium is denser than copper
but has a smaller atomic radius. Or (D) vanadium is denser than
copper and has a larger atomic radius.
This question is asking us to
compare the density and atomic radius of copper and vanadium. Vanadium and copper are in the
fourth period of the periodic table. They are in the d-block region of
the periodic table, and they are also classified as transition metals. As you go across the transition
elements from left to right, the number of protons in each element increases. The number of electrons also
increases. They fill the 3d orbitals and are
pulled closer to the nucleus. This causes a decrease in atomic
radii.
However, as we get to chromium, the
increased number of electrons in the 3d orbital generates enough repulsion between
the electrons to halt the decrease in atomic radii. The atomic radius values remain
essentially constant from chromium through to copper. If we represent this graphically,
it is clear that the atomic radii decreases but not in a uniform manner. It is also clear that copper has a
smaller atomic radius than vanadium. For this reason, we can rule out
options (A) and (C) as they state that vanadium has a smaller atomic radius than
copper.
We now need to focus on the density
of the elements. The trend in the densities is not
too dissimilar from the trend in atomic radii. There is a consistent increase in
density from scandium to chromium, just like there was a consistent decrease in
atomic radii from scandium to chromium. The density does continue to
increase from manganese to copper, but the change is not as dramatic. It is clear from the graph that
vanadium is less dense than copper. Therefore, option (D) is not the
answer to this question.
Therefore, the statement that
correctly compares the two d-block elements is (B); vanadium is less dense than
copper but has a larger atomic radius.
