Question

elements situated diagonally from each other on the periodic table (such as sodium/calcium or berlium/aluminum) often exhibit similar properties. explian why is this so

Answer 1

Since moving across the period or moving down the group of periodic table have opposite effects.

On moving across a period of the periodic table, the size of the atoms decreases while on moving down a group the size of the atoms increases. In the similar way, on moving across the period, the elements become progressively more covalent, more electronegative and less basic, whereas on moving down the group the elements become more ionic, less electronegative and more basic.

Thus, on both crossing the period by one element and descending a group by one element, the changes "cancel" each other out. And hence, elements with similar properties which have similar chemistry (of the diagonal members are similar).