JEE Main 2021
LEVELJEE Main
Visualized Solution
The Sigma Insight: Alkali Metals
The Real-World Magic of Alkali Metals
When we study the s-block elements, it is easy to get lost in the trends of ionization energies and atomic radii. But these elements are not just abstract concepts on the periodic table; they have fascinating and highly specific real-world applications.
In this problem, we are tasked with matching four alkali metals—Lithium, Sodium, Potassium, and Caesium—with their industrial uses. Let's break them down one by one.
Lithium
The Tough Alloy Builder
Lithium is the lightest metal, but when it teams up with lead, it creates something incredibly durable.
Lithium forms an alloy with lead known as 'white metal'. This alloy is exceptionally tough and resistant to wear and tear. Because of these mechanical properties, it is the perfect material for making bearings for motor engines.
So, we can confidently match Lithium (A) with motor engine bearings (V).
Sodium
The Nuclear Coolant
Next up is Sodium. You might know sodium as the metal that vigorously catches fire in water. But in its liquid state, it serves a much cooler purpose—literally.
Liquid sodium metal is an outstanding conductor of heat. In fast breeder nuclear reactors, immense amounts of heat are generated. Liquid sodium is pumped through the reactor core to absorb this heat and transfer it away safely, acting as a highly efficient coolant.
Therefore, Sodium (B) matches perfectly with the nuclear reactor coolant (III).
Potassium
The Breath of Fresh Air
Potassium has a very special chemical affinity. Its compounds, particularly potassium hydroxide () and potassium superoxide (), are incredibly greedy for carbon dioxide.
When passes through these potassium compounds, it is rapidly absorbed to form potassium carbonate. This property is a lifesaver in closed environments like submarines and space capsules, where exhaled must be continuously scrubbed from the air.
Thus, Potassium (C) is our absorbent (II).
Caesium
The Light Catcher
Finally, we have Caesium. As we move down the alkali metal group, the atomic size increases, and the outermost electron gets further away from the nucleus.
Caesium has the lowest ionization enthalpy among the stable alkali metals. This means its valence electron is held so loosely that even the energy from a photon of visible light is enough to knock it out. This phenomenon is the photoelectric effect.
Because it ejects electrons so easily, Caesium is the ultimate material for devising photoelectric cells. So, Caesium (D) matches with photoelectric cells (I).
Final Calculation
Let's put all our matches together:
Looking at our options, this exact sequence corresponds to option (d).
As a side note, the 'Treatment of cancer' option was a distractor. Cancer radiation therapy typically relies on radioactive isotopes of transition metals, like Cobalt-60, not alkali metals.
Similar Questions
JEE Main 2021
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Match List-I with List-II. Choose the correct answer form the options given below.
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A-(iv), B-(iii), C-(i), D-(ii)
(B)
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JEE Main 2021
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JEE Main 2021
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is used in space and submarines because it
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The metal that forms nitride by reacting directly with of air, is
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The main oxides formed on combustion of Li, Na and K in excess of air respectively are
(A)
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(B)
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(C)
, and
(D)
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