Problem 9 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Three elements \(\mathrm{X}, \mathrm{Y}\) and \(\mathrm{Z}\) are in the \(3^{\text {rt }}\) period of the periodic table. The oxides of \(X, Y\) and \(Z\), respectively, are basic, amphoteric and acidic. The correct order of the atomic numbers of \(X, Y\) and \(Z\) is : (a) \(\mathrm{Z}<\mathrm{Y}<\mathrm{X}\) (b) \(\mathrm{X}<\mathrm{Y}<\mathrm{Z}\) (c) \(\mathrm{X}<\mathrm{Z}<\mathrm{Y}\) (d) \(\mathrm{Y}<\mathrm{X}<\mathrm{Z}\)

Step-by-Step Solution

Answer

The answer is (b) \(X < Y < Z\).

Step 1: Understanding Elemental Properties in the Periodic Table

In the periodic table, elements in the same period show a gradual change in chemical properties from left to right. Specifically, oxides transition from basic (ionic) to amphoteric and then to acidic (covalent) across a period. This is key in determining the nature of elements' oxides.

Step 2: Identifying Period 3 Elements and Their Oxides

The third period of the periodic table includes elements from sodium (Na, atomic number 11) to argon (Ar, atomic number 18). These elements are: - Sodium (Na) - Magnesium (Mg) - Aluminium (Al) - Silicon (Si) - Phosphorus (P) - Sulfur (S) - Chlorine (Cl) - Argon (Ar) Among these, basic oxides are formed by sodium and magnesium, amphoteric oxide by aluminum, and acidic oxides by silicon, phosphorus, sulfur, and chlorine.

Step 3: Assigning Elements by Oxide Type

Given the oxides' nature: - Basic oxide (X): Possible elements are Na (sodium) or Mg (magnesium). - Amphoteric oxide (Y): Al (aluminium) is known for forming amphoteric oxides. - Acidic oxide (Z): Possible elements include Si (silicon), P (phosphorus), S (sulfur), and Cl (chlorine).

Step 4: Determining the Order of Atomic Numbers

Using their periodic sequence: - Aluminum (Al) with amphoteric oxides has atomic number 13. - Elements that form acidic oxides like Si, P, S, or Cl come after aluminum in the period. - Elements like Na or Mg, which form basic oxides, come before aluminum in the period. This establishes the order based on increasing atomic numbers as Na/Mg < Al < Si/P/S/Cl.

Step 5: Choosing the Correct Option

Select the option that reflects the increasing atomic number order, hence: \(<\text{basic (X), amphoteric (Y), acidic (Z)} >\).- Option (b) \(X < Y < Z \) aligns with the correct theoretical order.

Key Concepts

Elemental Properties

When considering the elemental properties of period 3 elements, we explore how their characteristics evolve across the periodic table. Period 3 elements, which range from sodium (Na) to argon (Ar), exhibit gradual changes in their properties due to increasing atomic numbers and variations in electron configurations. Some key trends in elemental properties across a period include:

• Atomic Radius: As we move from left to right, the atomic radius decreases. This is due to the increasing nuclear charge, which pulls the electrons closer to the nucleus.
• Ionization Energy: The energy required to remove an electron increases across a period, making it harder to ionize atoms as you move from sodium to argon.
• Electronegativity: Electronegativity, or the tendency of an atom to attract electrons, generally increases across a period. This trend is evident as we move from metallic to non-metallic elements.

Understanding these properties aids in predicting the chemical behavior and bonding nature of these elements.

Oxide Nature

The nature of oxides formed by period 3 elements provides insights into their elemental properties. As you progress from left to right across period 3, you observe a transition in the type of oxides formed—from basic, to amphoteric, to acidic. Basic Oxides: These are formed by metals like sodium (Na) and magnesium (Mg), which tend to form ionic compounds. Basic oxides react with acids to form salts and water. For example, magnesium oxide (MgO) is a classic basic oxide. Amphoteric Oxides: Unique to certain elements like aluminum (Al), these oxides can react with both acids and bases, exhibiting dual behavior. Aluminum oxide ( Al_2O_3 ) is the most commonly known amphoteric oxide. Acidic Oxides: Non-metals such as silicon (Si), phosphorus (P), sulfur (S), and chlorine (Cl) form acidic oxides, which generally react with bases to produce salts. For instance, sulfur dioxide ( SO_2 ) is a typical acidic oxide. Understanding oxide nature helps deduce the metallic or non-metallic character of an element.

Period 3 Elements

Period 3 elements are a fascinating set of elements in the periodic table. They include sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (Cl), and argon (Ar). Each of these elements displays distinct chemical properties that are valuable in understanding periodic trends.

• Sodium (Na) and Magnesium (Mg): These are highly reactive metals and are known for forming basic oxides.
• Aluminum (Al): As a metal, it forms in-between behavior oxides (amphoteric) and finds extensive use in various industries due to its light weight and strength.
• Silicon (Si) to Chlorine (Cl): Transitioning into non-metals, these elements are known for forming acidic oxides. They are used in a wide variety of applications such as semiconductor materials (in the case of silicon) and disinfectants (chlorine).
• Argon (Ar): As a noble gas, argon is chemically inert, making it ideal for use in environments where reactions need to be minimized, such as in light bulbs.

Each element's position in period 3 provides clues to its chemical reactivity and the types of compounds it can form. This makes period 3 a key area of study for understanding the broader trends of the periodic table.