Choose the correct statement.

In what properties do the first elements of a group differ from the subsequent elements of the same group?

Among the elements $B$,$Al$,$C$,and $Si$,
$(a)$ which element has the highest first ionisation enthalpy?
$(b)$ which element has the most metallic character? Justify your answer in each case.

Which of the following statements are not correct?
$A.$ The electron gain enthalpy of $F$ is more negative than that of $Cl$.
$B.$ Ionization enthalpy decreases in a group of the periodic table.
$C.$ The electronegativity of an atom depends upon the atoms bonded to it.
$D.$ $Al_2O_3$ and $NO$ are examples of amphoteric oxides.
Choose the most appropriate answer from the options given below:

Describe the periodicity of the first ionization enthalpy for elements with atomic numbers $1$ to $60$.

Which of the following statements is correct?