Which of the following is the first artificially prepared element ?

Question

UnlockIAS · Accepted Answer

Correct — A, Tc. The symbol stands for technetium, atomic number 43, and it is the first chemical element that human beings made rather than found. Mendeleev's 1871 table had left an empty box below manganese, and he predicted the missing element under the name eka-manganese; chemists hunted for it in ores for sixty years without success, because — as is now understood — every isotope of element 43 is radioactive and none is long-lived enough to have survived in the Earth's crust from the time the planet formed. It was finally made, not found. In 1937 Carlo Perrier and Emilio Segrè, working at Palermo, examined a molybdenum foil that had been bombarded with deuterons in Ernest Lawrence's cyclotron at Berkeley and sent to Segrè on request. Molybdenum is element 42; the added proton pushed it to 43, and the two chemists separated the new activity and established that it was a new element. They named it technetium, from the Greek tekhnetos, meaning artificial — the name is itself the answer to this question. The other three symbols are ordinary naturally occurring elements dug out of minerals in the eighteenth and nineteenth centuries, and they are on the paper purely because their symbols all begin with T. Note one honest refinement: minute traces of technetium have since been detected in uranium ores, produced continuously by the spontaneous fission of uranium, so 'does not occur in nature' is better stated as 'occurs only in vanishing traces as a fission product'. That does not touch the claim being tested, which is about the first element to be prepared artificially.

Why the other options are wrong — (b) Tellurium, element 52 — a naturally occurring metalloid first noticed in 1782 by Franz-Joseph Müller von Reichenstein in gold ores from Transylvania and named by Martin Heinrich Klaproth from the Latin tellus, 'earth'. It is mined, not manufactured, and today comes largely as a by-product of copper refining.  (c) Thallium, element 81 — discovered in 1861 by William Crookes, who spotted an unexpected bright green line while examining the residues of a sulphuric-acid plant with a spectroscope, and named it from the Greek thallos, a green shoot. A natural element identified by spectroscopy, and notoriously toxic.  (d) Thorium, element 90 — isolated by Jöns Jacob Berzelius in 1828 and named after the Norse god Thor. It is radioactive but entirely natural and comparatively abundant: India's monazite beach sands hold one of the world's largest reserves, which is the basis of the third stage of the Indian nuclear programme. Its radioactivity makes it the trap for anyone who equates 'radioactive' with 'man-made'.

Concept: Elements divide into those that exist on Earth because the planet formed with them and those that exist only because a laboratory made them. Everything up to uranium, element 92, occurs naturally in some quantity with two conspicuous gaps — technetium (43) and promethium (61) — whose isotopes are all radioactive with half-lives far too short to have survived the four-and-a-half billion years since the Earth's formation. Technetium was the first of the gaps to be filled artificially, in 1937, by bombarding a lighter nucleus with an accelerated particle in a cyclotron; promethium followed in 1945, identified in the fission products of a uranium reactor at Oak Ridge. Beyond uranium every element is synthetic: neptunium and plutonium in 1940, then the transuranics up to oganesson, element 118. The technique is always some form of the same thing — accelerate a projectile nucleus hard enough to fuse it with a target nucleus, then identify the tiny yield chemically or by its decay signature.

State PCS 2024 Q73 — Science & Technology PYQ with Answer

State PCS 2024 Q73 — Science & Technology PYQ with Answer