Value on Mulliken's scale = 2.8 x 4 = 11.2.

Electron gain enthalpy of Cl is more negative than that of F.

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 
1s ²  , 2s ²  , 3s² , 3p⁶ , 4s², 3d¹⁰ , 4p⁶ , 5s² , 4d¹⁰ ,  5p⁶ , 6s² ,4f¹⁴ , 5d¹⁰ , 6p⁶ , 7s² , 5f¹⁴ , 6d¹⁰ , 7p⁶ = 118.

Elements in which the last electron enters in the d-orbitals, are called d-block elements or transition elements. These elements have the general outer electronic configuration (n-1)d^1-10 ns^0-2 . Zn, Cd and H having the electronic configuration, (n-1)d¹⁰ ns² do not show most of the properties of transition elements. The d-orbitals in these elements are completely filled in the ground state as well as in their common oxidation states. Therefore, they are not regarded as transition elements. Thus, on the basis of properties, all transition elements are d-block elements are not transition elements.

Se and Te belong to 16 group and fourth and fifth period respectively whereas Br and I belong to 17 group and fourth and fifth period respectively. In a period ionisation energy increase but along a group, it decreases. Thus, the order of ionisation enthalpy is Te < I < Se < Br. i.e. Te has IE of 869 and Se has IE of 1142 kJ mol^-1.

Cu [ 0.122 nm ],Cu⁺ [0.096 nm],Cu²⁺ [0.072 nm].
∴ size ∝ \(\frac{1}{\text{positive charge}}\) 

Same group elements have similar valence shell electronic configuration. Therefore, have similar physical and chemical properties.

These names were given to gallium and germanium by Mendeleev because he thought that these elements will have similar properties as that of aluminium and silicon, respectively.

We see from Fig.,

that element with Z = 117, would belong to the halogen family (Group 17) and the electronic configuration would be [Rn] 5f ¹⁴6d¹⁰7s²7p⁵. The element with Z = 120, will be placed in Group 2 (alkaline earth metals), and will have the electronic configuration [Uuo]8s².

As we move from left to right in period, the number of valence electrons increases by one at each succeeding element but the number of shells remains same. Due to this, effective nuclear charge ivcreases.
More is the effective nuclear charge, more is the attraction between nuclei and electron.
Hence, the tendency of the element to lose electrons decreases, this results in decrease in metallic character.
Furthermore, the tendency of an element to gain electrons increases with increase in effective nuclear charge, so non-metallic character increases on moving from left to right in a period.

Electropositive character means tendency to give an electron to form cation. It varies directly with atomic radii. Thus, the correct order is Mg > fe > Cu.

The amount of energy released when 1 x 10¹⁰ atoms of chlorine in vapour state are converted to Cl^- ions, according to the equation.
Cl ( G ) + e^- \(\longrightarrow \) Cl^- ( g ) is 57.86 \(\times \) 10^-10 J
\(\therefore \)  The electron gain enthalpy of ghlorine, i.e. the amount of energy releaed ehen 1 mole ( 6.023 \(\times \) 10²³ ) atoms of chlorineare coverted into Cl^- ions according to the above equation will be
= -\(\frac { 57.86\times { 10 }^{ -10 } }{ 1\times { 10 }^{ 10 } } \times 6.023\times { 10 }^{ 23 }\)
= -348.49 \(\times\) 10³ J mol^-1
= -348.49 kJ mol^-
Now 1 eV/atom = 96.49 kj mol^-1
\(\therefore\)  Electron gain enthalpy of chlorine
= -\(\frac { 348.49 }{ 96.49 }\)
= - 3.61 eV/atom