Problem 2 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The noble gas that does NOT occur in the atmosphere is : [Main April 10, 2019 (II)](a) \(\mathrm{He}\) (b) \(\mathrm{Kr}\) (c) \(\mathrm{Ne}\) (d) \(\mathrm{Ra}\)

Step-by-Step Solution

Answer

Radium (\(\mathrm{Ra}\)) does not occur in the atmosphere.

Step 1: Understand Noble Gases

Noble gases are a group of chemical elements with similar properties that include being odorless, colorless, monatomic gases with very low chemical reactivity. The known noble gases are Helium (\(\mathrm{He}\)), Neon (\(\mathrm{Ne}\)), Argon (\(\mathrm{Ar}\)), Krypton (\(\mathrm{Kr}\)), Xenon (\(\mathrm{Xe}\)), and Radon (\(\mathrm{Rn}\)).

Step 2: Identify Noble Gases in the Atmosphere

Most noble gases are found in the Earth's atmosphere: \(\mathrm{He}\), \(\mathrm{Ne}\), \(\mathrm{Ar}\), \(\mathrm{Kr}\), \(\mathrm{Xe}\), and tiny amounts of \(\mathrm{Rn}\). These occur naturally due to slow radioactive decay.

Step 3: Identify Option (d) - Radium

Notice that option (d) is \(\mathrm{Ra}\), which is Radium, not Radon. Radium is not a noble gas and does not occur naturally in the atmosphere. Radium is a radioactive element typically found in uranium ore but is not present in gaseous form in the atmosphere.

Step 4: Conclusion

Since Radium is not a noble gas, and it does not occur in the atmosphere, it differs from the other choices which are actual noble gases.

Key Concepts

Atmospheric Gases

The Earth's atmosphere is a vast layer of gases surrounding the planet, providing essential components for life and protecting us from outer threats. Among these, noble gases capture the interest of many due to their unique characteristics and behaviors.Noble gases in the atmosphere include some common names you might recognize:

• Helium (\(\mathrm{He}\))
• Neon (\(\mathrm{Ne}\))
• Argon (\(\mathrm{Ar}\))
• Krypton (\(\mathrm{Kr}\))
• Xenon (\(\mathrm{Xe}\))
• Trace amounts of Radon (\(\mathrm{Rn}\))

These gases are present in small amounts, with Argon being the most abundant among the noble gases within our atmosphere. Noble gases are excellent subjects for study because they do not readily combine with other elements due to their stable electron configurations. This non-reactivity means they typically remain as isolated atoms, floating quietly within the atmospheric mix.
It’s fascinating to note that despite their rarity, these gases play specific roles, from scientific to practical applications, such as in lighting and welding.

Chemical Elements

Chemical elements are the building blocks of all matter, consisting of atoms with the same atomic number. The elements, including noble gases and others, form the extensive periodic table that categorizes them based on similar properties.Noble gases represent a particular group because of their

• Inertness
• Monatomic presence
• Colorless and odorless qualities

These properties make noble gases distinct from other groups in the periodic table. For example, though some elements like Radon (\(\mathrm{Rn}\)) can be seen in the atmosphere in trace amounts, Radium (\(\mathrm{Ra}\)), another chemical element discussed here, is not part of the noble gases group. Radium is indeed a metal found naturally in the Earth's crust, particularly in uranium and thorium ores, but it does not form a gas that mingles with atmospheric gases.

Understanding the characteristics of each element and distinguishing between similarly named ones, like Radon and Radium, is crucial because it helps clarify their roles in nature and potential applications, especially considering their radioactivity.

Radioactivity

Radioactivity is a natural process by which unstable atomic nuclei lose energy by emitting radiation. It's a key concept in nuclear chemistry and physics.Not all elements are radioactive, but in this context, both Radon and Radium are pertinent examples stemming from radioactive decay:

• **Radon (\(\mathrm{Rn}\)):** A noble gas that occurs naturally as a result of the radioactive decay of Radium. It is found in minor amounts in the atmosphere and is known for its radioactivity, but its gaseous form allows it to disperse easily.
• **Radium (\(\mathrm{Ra}\)):** A far heavier element, not a noble gas, is highly radioactive. It's found in solid form due to its metallic nature and arises from the decay of uranium and thorium. Unlike noble gases, it does not exist naturally in the air.

The study of radioactivity is essential since it has profound implications on our health through radiation exposure, and it forms the basis for various technologies, including nuclear energy and medical radiography. Proper comprehension of radioactivity, particularly distinguishing gaseous and solid radioactive elements, contributes to safer handling and use of these materials in various human endeavors.