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Question
The diagonal relationship in Be and Al is due to ______.
Options
similar ionisation enthalpy
similar metallic character
similar ionic size and charge/radius ratio
similar electronegativity
Solution
The diagonal relationship in Be and Al is due to similar ionic size and charge/radius ratio.
Explanation:
Be and Al have a diagonal relationship because their ionic sizes and charge/radius ratios are similar. In general, as you move from left to right over time, the ionic charge grows to its maximum and then falls, while the ionic size decreases, increasing the polarising power (Fajan's rule).
Moving down a group, on the other hand, the ionic charge remains constant while the ionic size grows. As a result, polarizing power diminishes. These two effects partially balance each other when moving diagonally, therefore their attributes do not alter significantly.
