Question 6 of 48intermediate🔍 AnalyzeShort Answer2 marks

The first ionization enthalpy (ΔᵢH) values of the third period elements, Na, Mg and Si are respectively 496, 737 and 786 kJ mol⁻¹. Predict whether the first ΔᵢH value for Al will be more close to 575 or 760 kJ mol⁻¹? Justify your answer.

Correct Answer

The first ionization enthalpy (ΔiH\Delta_i H) value for Al will be more close to 575 kJ mol−1^{-1}.

Exercise: IN-TEXT QUESTIONS (PROBLEMS) | Q: Problem 3.6 | (Page 16)
For More Understanding

Explanation

The value for Al should be lower than that of Mg (737 kJ mol−1^{-1}) because of effective shielding of 3p electrons from the nucleus by 3s-electrons. Since the outermost electron in Al is in the 3p orbital, it experiences less effective nuclear charge and is easier to remove compared to the electrons in the 3s orbital of Mg.

Solution Steps

  1. Step 1: Identify the position of Al in the third period, which comes after Mg and before Si.

  2. Step 2: Compare the expected ΔiH\Delta_i H of Al with Mg. The value for Al should be lower than that of Mg (737 kJ mol−1^{-1}).

  3. Step 3: Justify the lower value using the concept of effective shielding of the 3p electrons from the nucleus by the 3s-electrons, making the 3p electron easier to remove.

  4. Step 4: Conclude that the value will be closer to 575 kJ mol−1^{-1} rather than 760 kJ mol−1^{-1}.

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