Identify the incorrect statement from the following:
- A.The largest and the smallest species among \ce{Mg}, \ce{Mg^2+}, \ce{Al} and \ce{Al^3+} are \ce{Al} and \ce{Mg^2+} respectively.✓
- B.The IUPAC name of the element with atomic number $107$ is Unnilseptium.
- C.The similarity in behaviour of \ce{Li} with \ce{Mg} is referred to as the 'diagonal relationship'.
- D.The oxidation state and covalency of \ce{Al} in \ce{[AlCl(H2O)5]^2+} are $3$ and $6$, respectively.
Correct Answer
(A) The largest and the smallest species among \ce{Mg}, \ce{Mg^2+}, \ce{Al} and \ce{Al^3+} are \ce{Al} and \ce{Mg^2+} respectively.
Solution & Explanation
\textbf{Answer:} (A) The largest and the smallest species among \ce{Mg}, \ce{Mg^2+}, \ce{Al} and \ce{Al^3+} are \ce{Al} and \ce{Mg^2+} respectively. \textbf{Solution:} Among \ce{Mg}, \ce{Mg^2+}, \ce{Al} and \ce{Al^3+}, the largest is the neutral \ce{Mg} (more electrons and weaker effective nuclear pull than \ce{Al}), and the smallest is \ce{Al^3+} (highest charge, fewest electrons). So statement A — claiming \ce{Al} is largest and \ce{Mg^2+} smallest — is incorrect. The other statements are correct: (B) the IUPAC name for $Z=107$ is Unnilseptium; (C) the \ce{Li}-\ce{Mg} similarity is the diagonal relationship; (D) in \ce{[AlCl(H2O)5]^2+} the oxidation state of \ce{Al} is $+3$ and its covalency is $6$.