Select the correct statements from the following:
$(a)$ Effective nuclear charge for nitrogen is $3.90$
$(b)$ $IP$ of $Ne$ is more than $Na^{+}$
$(c)$ Order of electronegativity $sp > sp^2 > sp^3$
$(d)$ Order of acidic character $NH_3 < PH_3 < AsH_3$

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.

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:

An element has the electronic configuration $1s^2 2s^2 2p^6 3s^2 3p^4$. Predict its period,group,and block.

Which of the following statements are correct?
$(i)$ First ionisation enthalpy of $He < $ Second ionisation enthalpy of $Li$.
$(ii)$ $Li$ has the highest second ionisation enthalpy.
$(iii)$ All $d$-block elements are transition elements.
$(iv)$ The only alphabet not found in the periodic table is the letter '$J$'.
$(v)$ Francium concentration is $\sim 10^{-18} \ ppm$ on Earth.

Which of these does not reflect the periodicity of the elements?