Question

Which is the first man-made element?
A. Sc
B. Os
C. Tc
D. Zr

Answer 1

Hint:Man-made elements are radioactive in nature that were not discovered occurring in nature but as artificially produced isotopes. The correct option is the only element just below uranium which does not present on Earth.

Complete step-by-step answer:
A) The chemical element scandium (Sc) is classified as a transition metal and rare earth.
 B) Osmium (Os) is a chemical element and its atomic number is 76. It is a hard and brittle by nature, bluish-white colour transition metal in the platinum group that is actually found as a trace element in alloys, mainly in platinum ores.
 C) Technetium (Tc) is the only element just below uranium which does not present on Earth. It is a synthetic element which is man-made and produced in a particle accelerator. For a long time, it has been known that an element with atomic number 43 must exist, depending on an empty spot in the periodic table.
 D) Zirconium (Zr) is a chemical element having atomic number 40, which is located in group−4 from the periodic chart of elements. It is a hard metal, resistant to corrosion and quite the same as steel.

Additional Information:
The gamma-ray emitting technetium-99m (metastable) is highly used for medical diagnostic studies. Many chemical forms which are generally used to display various parts of the body. Technetium is known as a remarkable corrosion inhibitor for steel, and adding mainly small amounts can be able to provide excellent protection.
Technetium actually has no biological role. Technetium does not occur naturally itself in the biosphere and so normally never provides a risk. All technetium compounds should be considered as highly toxic, largely due to its radiological toxicity.
If you spent all day wearing it as a hat or breathed it in as dust, it would surely be able to kill anyone. One of the main characteristics of technetium is that it is a very light element with no stable isotopes.

Hence, Option C is correct.

Note:History of these chemical compounds should be known for answering as they are very important in aspects of chemistry. Also man-made elements are radioactive in nature and for a long time, Technetium is known that an element with atomic number 43 must exist.