Noble gases having completely filled electronic configuration so neither accept nor lose their electron readily and hence they are chemically inert in nature.

In the present set up of the long form of the periodic table, we have eighteen groups, seven periods (i.e. principal quantum number, n = 7) and four blocks (s, p, d and f -block elements).
Therefore, the maximum number of elements which can be accommodated in the present set up of the long form of the periodic table in accordance with Aufbau principle is
1s2, 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰,
5p⁶, 6s², 4f¹⁴, 5d¹⁰, 6p⁶, 7s², 5f¹⁴, 6d¹⁰, 7p⁶ = 118.

Electronic configuration of the element is 3d¹ 4S².
The element belongs to fourth period and group 3.
The element is scandium (Z = 21).

(i) Lithium and beryllium form more covalent compounds, unlike the alkali and alkali earth metals which predominantly form ionic compounds.
(ii) The elements of the second period have only four orbitals (2s & 2p) in the valence shell and have a maximum co-valence of 4, whereas the other members of the subsequent periods have more orbitals in their valence shell and shows higher valences. For example, boron forms BF₄^- and aluminium forms AIF₆^3-.

(i) Due to low bond dissociation enthalpy, high electronegativity and large negative electron gain enthalpy, halogen have a strong tendency to accept electrons and thus get reduced.
X²+2e^- ⟶ 2X^-
(ii) The ready acceptance of an electron is due to the strong oxidising nature of halogens.
(iii) F₂ is the strongest oxidising halogen and it oxidises other halide ions in solution or even in the solid phase. In general, a halogen oxidises halide ions of higher atomic number.
(iv) Hence, the oxidising ability of halogens decreases from fluorine to iodine as :
F₂ > Cl₂ > Br₂ > I₂

In the periodic table vertical columns are called groups.
Elements in the same vertical column possess similar number of electrons in the outer orbitals.
∴ Elements a and c belongs to group 18
Elements b and d belongs to group 13

(i) According to aufbau's principle 5th period has nine orbital (one 5s, five 4d and three 6p) to be filled.
(ii) Nine orbitals can accommodate a maximum of 18 electrons. Hence fifth period of the periodic table should has 18 elements from rubidium (2 = 37) to Xenon (Z = 54).

Z = 118; [₈₆Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶
In the periodic table the element with Z = 118 is located in p-block,
Period no = 7 (as n = 7 for valence shell)
Group no. = 18 (group no = 10+ ns electrons + np electrons) (n - outer most shell)

(i) Electronic configuration is the arrangement of electrons in an atom. The outermost electron shell is often referred to as the "valence shell"determines the chemical properties.
(ii) Ionization energy and electron affinity is the amount of energy released or required in pulling out or adding an electron to a neutral atom. So both depend on electronic configuration of the element.

Ionisation energy is the amount of energy required to remove the electron from the ground state (EI) to excited state (E^∞)
E₁=-2.18 x 10^-18 J; E_∞=0
ΔE=E_∞-E₁
=0-(-2.18 x 10^-18 J)=2.18 x 10^-18 J
I.E per hydrogen atom = 2.18 x 10^-18 J
I.E per mole of H-atom =2.18 x 10^-18 J x 6.023 x 10²³
=13.13 x 10⁵ J mol^-1