Question

Which of the following statements are correct? I. In the third period, two elements have higher ionization enthalpy than the element immediately following them in the same period. II. Electronegativity of carbon is higher than that of phosphorus. III. An element \(X\) belongs to group 14 and period 3. The number of electrons present in it is \(14\).

• A. I, II, III
• B. I, II only
• C. II, III only
• D. I, III only

Hint:

Important third-period ionization enthalpy exceptions: \[ Mg \gt Al \] \[ P \gt S. \] Also remember: \[ \text{Group 14, Period 3} \Rightarrow \text{Si} \ (Z=14). \]

Answer 1

The Correct Option is A

Statement I: Across the third period, ionization enthalpy generally increases, but there are two exceptions: \[ Mg \gt Al \] and \[ P \gt S. \] Thus, two elements (\(Mg\) and \(P\)) have higher ionization enthalpy than the element immediately following them. \[ \boxed{\text{Statement I is correct}} \]

Statement II: Electronegativity values: \[ \chi_C \approx 2.55 \] \[ \chi_P \approx 2.19 \] Hence, \[ \chi_C \gt \chi_P. \] \[ \boxed{\text{Statement II is correct}} \]

Statement III: Group 14 and Period 3 corresponds to \[ \text{Silicon (Si)}. \] Atomic number of silicon: \[ Z=14. \] For a neutral atom, \[ \text{Number of electrons}=Z=14. \] \[ \boxed{\text{Statement III is correct}} \]

Conclusion: All three statements are true. \[ \boxed{\text{I, II, III}} \] \[ \boxed{\text{Answer = (A)}} \]