Which property decreases from left to right across the periodic table and increases from top to bottom?
$(i)$ Atomic radius
$(ii)$ Electronegativity
$(iii)$ Ionisation energy
$(iv)$ Metallic character

The number of the following pairs of elements which exhibit a diagonal relationship is:
$1. B \text{ and } Si$
$2. Be \text{ and } Al$
$3. Li \text{ and } Mg$
$4. Al \text{ and } S$

Which of the following statements are correct?
$A.$ The process of the addition of an electron to a neutral gaseous atom is always exothermic.
$B.$ The process of removing an electron from an isolated gaseous atom is always endothermic.
$C.$ The $1^{st}$ ionization energy of boron is less than that of beryllium.
$D.$ The electronegativity of $C$ is $2.5$ in $CH_4$ and $CCl_4$.
$E.$ $Li$ is the most electropositive among elements of group $I$.
Choose the correct answer from the options given below:

Which group is called the buffer group of the periodic table?

Which of the following pairs shows a diagonal relationship?

The statement that is true for the long form of the periodic table is