Arrange the following transition elements of the first series in increasing order of their densities
(A) Sc
(B) V
(C) Zn
(D) Cu
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A), (B), (C), (D)
The density of a metal depends on how much mass is packed into how small a volume. Across the 3d series two changes act together:
Atomic mass increases steadily from Sc to Zn.
Metallic radius decreases from Sc to about the middle of the series and stays small up to Cu, because the added 3d electrons shield the outer electrons poorly and strong metallic bonding pulls the atoms close.
So the density rises from scandium to copper. Zinc breaks the trend: with a completely filled 3d10 set, it has no unpaired d electrons for metallic bonding, its radius is larger (137 pm against 128 pm for Cu), and its density falls back.
The densities (g cm−3) of the four metals are:
(A) Sc: 3.43, the lightest, at the start of the series.
(B) V: 6.07.
(C) Zn: 7.1, lower than copper.
(D) Cu: 8.9, the densest of the four.
In increasing order of density:
\( \displaystyle \text{Sc}\,(3.43) \lt \text{V}\,(6.07) \lt \text{Zn}\,(7.1) \lt \text{Cu}\,(8.9) \)
Shortcut: Scandium, the first and lightest element, must come first: Options (2) and (4). Copper is denser than zinc, so it comes last, which leaves Option (4).
NCERT (2026-27 edition):
Physical Properties – …
