Introduction of p- block

• P block is present at extreme right of periodic table.
• It has general electronic configuration ns²np^1-6.
• It includes solids, liquids and gases.
• The elements of this group are metal, non- metal and metalloids.
• If we move along period in periodic table, non-metallic character increases and if we move down the group, the non-metallic character decreases.
• In this group: As we move down, the lower oxidation state becomes more stable due to” Inert pair effect.”

Inert pair effect : It is “reluctance in the participation of s electrons in bond formation due to poor shielding effect by d and f orbital .As a result, s electrons are tightly bounded .

1^st member is different from its congeners due to:

• Small size
• Highest ionization energy.
• High electro-negativity.
• No vacant d orbital.
• They show maximum co-valence of 4 because of no vacant d orbital.
• First member also has tendency to form multiple bonds because in them p can takes place (because of its small size) .

Physical properties of group 13:

1. Atomic size and Ionic radii:

• If we compare group 11 with group 13, then group 13 is smaller due to increased nuclear charge.

           Example: Out of Be and B ,Boron is smaller .

• Down the group, size increases because nuclear charge decreases (due to addition of new shell).
• Expected order : B <Al<Ga<In<Tl
• But actual the order is :BGa<In<Tl
• The reason behind it: Is due to filling of d-orbital in Gallium, the effective nuclear charge on valence electron increases (because of poor shielding effect by d and f orbital).
• Therefore, nucleus pull electron more effectively and size decreases.
• That is the reason, Gallium is smaller than Aluminum (because Gallium has d-electrons and Aluminum doesn’t have) .

2. Ionization energies

• If we compare ionization energy of group 13 and group 2, we can say that the ionization of group 13 is more, because of their small size and increased nuclear charge.
• But actually group 2 has high ionization energy, than group 13 due to completely filled s orbital in group 2 elements.
• In case of Be and B, the electronic configuration of Be is 1s²2s² and in boron it is 1s²2s²2p¹. So, due to this reason the ionization energy of Boron is less than Beryllium.

Down the group ionization energy decreases, as the size increase and nuclear charge decrease.

So , the expected order is : B>Al>Ga>In>Tl

But actually it is : B>AlIn>Tl due to poor shielding effect by d electrons in gallium.

3. Electronegativity: If we compare with group 2, they are more electronegative due to increased nuclear charge.

Along group: It decreases, but the expected order is this B>AlIn>Tl.

 This is due to poor shielding effect.

4. Electropositive character: As compared to group 2, they are less electropositive due to increased nuclear charge.

Down the group: The size increases. Therefore, metallic character increases.

B                        Al                        Ga                 In                        Tl

_{Non metal                 amphoteric                      less metallic                    metallic                     metallic}

5. Oxidation state: It depends on electronic configuration .As their electronic configuration is ns² np.So, oxidation states shown by them are +3,+1.

• Boron: Shows exceptional behavior because of its small size and high ionization energy .It actually faces difficulty in loosing electrons .Therefore, it forms covalent bond.

B      Al      Ga   In  Tl

_{(+3)   (+3)    (+3,+1) (+3,+1)  (+1)}                                                                                     

This is basically due to inert pair effect.