As we go from left to right in period $2$ of the periodic table,the gram atomic volume of the elements:

What is meant by diagonal relationship?

The ionisation enthalpies of elements of the second period are given below: Ionisation enthalpy / $kcal \, mol^{-1}$: $520, 899, 801, 1086, 1402, 1314, 1681, 2080$. Match the correct enthalpy with the elements and complete the graph given in Fig. Also,write the symbols of the elements with their atomic numbers.

Observe the following statements:
$I$. The physical and chemical properties of elements are periodic functions of their electronic configuration.
$II$. Electronegativity of fluorine is less than the electronegativity of chlorine.
$III$. Electropositive nature decreases from top to bottom in a group.
The correct answer is:

Identify the incorrect order corresponding to the mentioned property.

Assertion : Best diagonal relationship is shown between $Be$ and $Al$.
Reason : Ionization energy of $Be$ is almost the same as that of $Al$.