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:

Use the periodic table to answer the following questions.
$(a)$ Identify an element with five electrons in the outer subshell.
$(b)$ Identify an element that would tend to lose two electrons.
$(c)$ Identify an element that would tend to gain two electrons.
$(d)$ Identify the group having metal,non-metal,liquid as well as gas at room temperature.

Compare the ionization enthalpy and electron gain enthalpy values of the elements given below:

Element Description	Element	$\Delta_{i}H_1$	$\Delta_{i}H_2$	$\Delta_{eg}H$
$(i)$ Most reactive non-metal	$(A)$	$419$	$3051$	$-48$
$(ii)$ Most reactive metal	$(B)$	$1681$	$3374$	$-328$
$(iii)$ Least reactive element	$(C)$	$738$	$1451$	$-40$
$(iv)$ Metal forming dihalide	$(D)$	$2372$	$5251$	$+48$

What are the differences between the first element of a group and the subsequent elements in the same group?

The ground state electronic configurations of the elements,$U, V, W, X,$ and $Y$ (these symbols do not have any chemical significance) are as follows:
$U: 1s^2 2s^2 2p^3$
$V: 1s^2 2s^2 2p^6 3s^1$
$W: 1s^2 2s^2 2p^6 3s^2 3p^2$
$X: 1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^2$
$Y: 1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6$
Determine which sequence of elements satisfies the following statements:
$(i)$ Element forms a carbonate which is not decomposed by heating
$(ii)$ Element is most likely to form coloured ionic compounds
$(iii)$ Element has the largest atomic radius
$(iv)$ Element forms only acidic oxide

Which of the following orders is correct according to the given property?