Question 7 of 48intermediate🔍 AnalyzeShort Answer2 marks

Which of the following will have the most negative electron gain enthalpy and which the least negative? P, S, Cl, F. Explain your answer.

Correct Answer

The element with the most negative electron gain enthalpy is chlorine (Cl), and the element with the least negative electron gain enthalpy is phosphorus (P).

Exercise: IN-TEXT QUESTIONS (PROBLEMS) | Q: Problem 3.7 | (Page 17)
For More Understanding

Explanation

Electron gain enthalpy generally becomes more negative across a period from left to right due to increasing effective nuclear charge, and less negative down a group. Among the given elements, P is the leftmost, making its electron gain enthalpy the least negative. While F is to the right of Cl in the period, adding an electron to its smaller 2p2p-orbital causes significant electron repulsion compared to adding an electron to the larger 3p3p-orbital of Cl. Thus, Cl has the most negative electron gain enthalpy.

Solution Steps

  1. Step 1: Identify the general trend: electron gain enthalpy becomes more negative across a period and less negative down a group.

  2. Step 2: Note the exception: adding an electron to the smaller 2p2p-orbital of F leads to greater repulsion than adding to the larger 3p3p-orbital of Cl.

  3. Step 3: Conclude that Cl has the most negative electron gain enthalpy, while P (being the leftmost element) has the least negative.

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