(i); Due to the ineffective shielding of valence electrons by the intervening 3d electrons, the effective nuclear charge on Ga is slightly higher than that on Al.

Hence the ΔH_ionization of gallium is slightly higher than that of Al.

(ii); Boron has three electrons in the valence shell. Because of its small size and a high sum of the first three ionization enthalpies, it doesn’t form B³⁺ ion.

(iii); Aluminum has empty d-orbital to accommodate the electrons from the fluorine atom but boron has no empty d-orbital to accommodate the electrons.

Thus,aluminum forms [AlF₆]^3- ion but boron does not form [BF₆]^3- ion.

(iv); Pb is the member of the group 14 of the periodic table (carbon family).The valence shell electronic configuration of this element is ns² np² type. Pb can show variable oxidation states of +2 and +4.

On moving top to bottom in the group, the lower oxidation state i.e +2 is more stable than the higher one due to the inert pair effect.

Thus, Pbdue to the inert pair effect (poor shielding of the inner electronic orbitals) shows +2 as a stable oxidation state rather than +4.

Thus, PbX₂ is more stable than PbX₄.

(v); Sn and Pb are the members of the group 14 of the periodic table (carbon family).The valence shell electronic configuration of these elements is ns² np²type.All these elements contain four electrons in the valence shell.These elements show variable oxidation states of +2 and +4.

On moving top to bottom in the group, the lower oxidation state i.e +2 is more stable than the higher one due to the inert pair effect.

Thus, Pbdue to the inert pair effectshows +2 as stable oxidation state rather than +4. So, by accepting two electrons Pb⁴⁺ will get converted into Pb²⁺.

Thus, Pb⁴⁺ by undergoing self-reductionacts as an oxidizing agent.

In the case of Sn, the inert pair effect is very less,the +4 oxidation state is more stable than +2.

Thus,by losing two electrons,Sn²⁺ gets converted into Sn⁴⁺ and can act as reducing agent.

(vi); Fluorine has a very small size thus the electrons of the 2p orbital experiences the interelectronic repulsion.

Thus, the electron coming out of the orbital does not experience much of the attraction from the nucleus hence the negative electron gain enthalpy of fluorine is less than that of chlorine.

(vii); Due to the poor shielding effect of the inner electronic orbitals, the +3 oxidation state of Tl is less stable than its +1 oxidation state.

Since in Tl(NO₃)₃, the oxidation state of Tl is +3, therefore, it can easily gain two electrons to form TlNO₃ in which the oxidation state of Tl is +1.

Consequently, Tl(NO₃)₃ acts as an oxidizing agent.

(viii);The catenation property depends on two factorsone is atom size and second is the M-M bond energy. Smaller the atomic radii and the greater the M-M bond energy, the greater is the tendency to show catenation.

On moving down a group the atomic size increases and the M-M bond energy also reduces.

Thus, Carbon shows the catenation whereas lead does not.

(ix);BF₃ does not hydrolyze completely. Instead, it hydrolyzes incompletely to form boric acid and fluoroboric acid. This is because the HF first formed reacts with H₃BO₃.

These equations can be written as:

Thus, BF₃ does not hydrolyze completely.

(x); Graphite is a macromolecule that is made up of hexagonal carbon rings.

This property is due to the catenation of the carbon atoms. Catenation is the tendency of an element to form covalent bonds between its atoms.

The catenation property depends on two factorsone is atom size and second is the M-M bond energy. Smaller the atomic radii and the greater the M-M bond energy, the greater is the tendency to show catenation.

On moving down a group the atomic size increases and the M-M bond energy also reduces.

Thus, Carbon shows the catenation whereas silica does not.