Heavier element in the grp. have lesser o.s so in pb is the heavier element to respective grp. that why it can more stable in low o.s due to poor sheilding effect on the presence of d and f orbital

Introduction:

In order to understand why PbCl4 is less stable than SnCl4 and PbCl2 is more stable than PbCl4, it is important to analyze the electronic configuration and bonding characteristics of these compounds.

Comparison of electronic configurations:

- PbCl4: Lead (Pb) has a valence electron configuration of 6s2 6p2. In PbCl4, each chlorine (Cl) atom donates one electron to form a covalent bond, resulting in the formation of four Pb-Cl bonds. The lead atom thus attains an expanded octet configuration, which is energetically unfavorable.

- SnCl4: Tin (Sn) also has a valence electron configuration of 5s2 5p2. In SnCl4, each chlorine atom donates one electron to form a covalent bond, resulting in the formation of four Sn-Cl bonds. Similar to PbCl4, tin also attains an expanded octet configuration. However, in the case of SnCl4, the expansion of the octet is more stable due to the presence of a vacant 5d orbital.

- PbCl2: Lead (Pb) has a valence electron configuration of 6s2 6p2. In PbCl2, each chlorine atom donates one electron to form a covalent bond, resulting in the formation of two Pb-Cl bonds. The lead atom in PbCl2 attains a stable octet configuration, which is energetically favorable.

Bonding characteristics:

- PbCl4: The formation of four Pb-Cl bonds in PbCl4 leads to the expansion of the lead atom's octet, resulting in a less stable compound. The presence of an expanded octet creates a strain on the atomic structure, making PbCl4 less stable.

- SnCl4: Similar to PbCl4, SnCl4 also has an expanded octet due to the formation of four Sn-Cl bonds. However, the expansion of the octet is more stable in tin due to the presence of a vacant 5d orbital. This allows for better accommodation of the extra electrons, leading to a relatively higher stability compared to PbCl4.

- PbCl2: In PbCl2, the formation of two Pb-Cl bonds allows the lead atom to attain a stable octet configuration. The absence of an expanded octet makes PbCl2 more stable compared to PbCl4. The stable octet configuration is energetically favorable and contributes to the overall stability of the compound.

Conclusion:

In summary, PbCl4 is less stable than SnCl4 and PbCl2 is more stable than PbCl4 due to the electronic configuration and bonding characteristics of these compounds. PbCl4 and SnCl4 have expanded octets, but the presence of a vacant 5d orbital in tin allows for better accommodation of the extra electrons, resulting in a relatively higher stability. PbCl2, on the other hand, attains a stable octet configuration, which is energetically favorable and contributes to its greater stability compared to PbCl4.