Question

If first ionization enthalpy (\(\Delta H\)) values of Na, Mg and Si are respectively 496, 737, and 786 kJ/mol, the first ionization enthalpy value of Al (in kJ/mol) will be:

• A. 575
• B. 760
• C. 400
• D. 790

Hint:

Ionization enthalpy increases across a period from left to right. Aluminum, being between magnesium and silicon, will have an ionization energy close to magnesium’s but slightly higher, thus estimated around 575 kJ/mol.

Answer 1

The Correct Option is A

Step 1: Understand the Periodic Trend of Ionization Enthalpies Ionization enthalpy generally follows periodic trends: - Ionization energy increases across a period (from left to right). - Ionization energy decreases as we move down a group (from top to bottom). 

Step 2: Analyze the Given Data From the question, we are given the following values for the first ionization enthalpy of the elements: - Sodium (Na): 496 kJ/mol - Magnesium (Mg): 737 kJ/mol - Silicon (Si): 786 kJ/mol Aluminum (Al) lies between magnesium (Mg) and silicon (Si) in the periodic table. 

Step 3: Estimate the Ionization Enthalpy of Aluminum Since aluminum (Al) is in the same period as silicon (Si) and magnesium (Mg), its first ionization enthalpy will be between the values for magnesium and silicon. - The first ionization enthalpy of magnesium is 737 kJ/mol. - The first ionization enthalpy of silicon is 786 kJ/mol. Since aluminum lies between magnesium and silicon, its ionization enthalpy will be closer to that of magnesium, but slightly higher than 737 kJ/mol. A reasonable estimate for the first ionization enthalpy of aluminum would be 575 kJ/mol. 

 

Step 4: Final Answer Thus, the first ionization enthalpy value of aluminum (Al) is: \[ \boxed{575 \, \text{kJ/mol}} \]