Question

Find the odd one out.
A.Constantan
B.Manganin
C.Nichrome
D.Chromium

Answer 1

Hint: We should look for the class of compounds or elements that the given options belong to. Among these, the odd one out is the one which is an element belonging to the d-block elements in the periodic table. While the other are alloys of metals.

Complete step by step answer:
Constantan is an alloy of copper and nickel. It is silvery-white in colour and is known as the most versatile alloy available. It is known for its property of offering high resistivity over a wide temperature range. That is, its resistivity does not change much for a wide range of temperature, due to which it is used for a variety of electrical purposes.
Its composition varies within a range but mostly it has $60\% $ copper and $40\% $ nickel.
Manganin is also an alloy made up of copper, manganese and nickel. It is used in a number of electrical devices due to its very low temperature coefficient of resistance. That is, its resistance does not change much with temperature.
The percentage of copper, manganese and nickel are about $84\% $, $12\% $ and $4\% $ respectively.
Nichrome as the name suggests is an alloy of nickel and chromium. It is known for its high resistance to heat and electricity. It is most desired for its property of high resistance to corrosion and high melting point.
It is generally composed of $80\% $ nickel and $20\% $ chromium, but sometimes has some amount of iron mixed with it.
Chromium is an element belonging to the ${4^{th}}$ period and ${6^{th}}$ group of the periodic table. It is a member of the d-block elements and the first transition metal series. It has atomic number $24$ and has electronic configuration $[Ar]3{d^5}4{s^1}$.
Since, constantan, manganin and nichrome are alloys of metal, while chromium is an element. Therefore, chromium is the odd one out.

Hence option D is correct.

Note:
Alloys are the compounds which are formed by the combination of different metals. Some of the common alloys are steel, solder, brass, bronze, etc. Alloys are formed to achieve certain desired properties in materials that cannot be achieved by the use of pure elements. For example, nichrome wires when heated do not become brittle and break easily, because on heating it forms a layer of chromium oxide which prevents the wire from oxidizing.