Which of the following sets is incorrect?

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 of the following is incorrect for the indicated property?

Which of the following orders is not correct about the property shown against it?

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

Fill in the blanks:
$(i)$ Atoms and ions having the same number of electrons are known as ........... .
$(ii)$ The quantitative measure of the tendency of an element to lose an electron is called ........... .
$(iii)$ The screening effect is also known by the name ........... .
$(iv)$ The enthalpy change when a gaseous neutral atom forms a negative ion is called ........... .