Question

Statement I: Along the period, the chemical reactivity of the element gradually increases from group 1 to group 18.
Statement II: The nature of oxides formed by group 1 element is basic while that of group 17 elements is acidic.
In the light of the above statements, choose the most appropriate from the questions given below:

• A. Both statement-I and statement-II are true
• B. Statement-I is true and statement-II is false
• C. Statement-I is false and statement-II is true
• D. Statement-I and statement-II both are false

Answer 1

The Correct Option is C

Statement I is incorrect. Chemical reactivity does not increase along the period. Instead:

For metals (on the left side of the periodic table), chemical reactivity decreases as we move across the period because ionization energy increases.

For nonmetals (on the right side of the periodic table), chemical reactivity increases as we move across the period due to higher electronegativity and electron affinity.

Thus, the chemical reactivity shows no uniform trend across the period, and the statement is false.

Statement II is correct. The oxides formed by:

• Group 1 elements (alkali metals) are basic in nature because these elements form oxides like Na₂O and K₂O, which react with water to form strong bases (e.g., NaOH).
• Group 17 elements (halogens) are acidic in nature because their oxides, like Cl₂O₇, react with water to form strong acids (e.g., HClO₄).

Thus, Statement II is true.

Thus, the evaluation of the statements leads to the conclusion that: Statement I is false while Statement II is true, making the correct answer:

Answer 2

Evaluate the two given statements regarding trends in chemical reactivity across a period and the nature of oxides formed by different groups.

Concept Used:

Chemical reactivity across a period is not a monotonic trend. It depends on the specific type of reaction (e.g., tendency to lose electrons, gain electrons, or form covalent bonds). The nature of an oxide (acidic, basic, or amphoteric) is determined by the element's position in the periodic table and its electronegativity.

Step-by-Step Solution:

Step 1: Analyze Statement I: "Along the period, the chemical reactivity of the element gradually increases from group 1 to group 18." This statement is incorrect. Chemical reactivity does not increase uniformly. For metals (e.g., Groups 1, 2), reactivity is high at the left and decreases across the period as the tendency to lose electrons decreases. For non-metals (e.g., Groups 16, 17), reactivity is high at the right and relates to the tendency to gain electrons. Group 18 (Noble gases) are largely inert. Therefore, there is no single, gradually increasing trend in reactivity from Group 1 to Group 18.

Step 2: Analyze Statement II: "The nature of oxides formed by group 1 element is basic while that of group 17 elements is acidic." This statement is correct. Group 1 elements (alkali metals) form strongly basic oxides (e.g., Na₂O) because they are highly electropositive. Group 17 elements (halogens) form acidic oxides (e.g., Cl₂O₇) because they are highly electronegative.

Step 3: Determine the relationship between the statements. Statement I is false. Statement II is true. A false statement cannot be explained by a true one, and they are independent facts about periodic trends.

Thus, Statement I is false and Statement II is true.