How do the +2 and +4 oxidation states differ in carbon group compounds?

In the carbon group (Group 14), the +2 and +4 oxidation states represent different bonding arrangements of the four valence electrons ($n{s}^{2}n{p}^2$). The primary difference between these states lies in the stability of the $n{s}^2$ electron pair, which increases as the atomic number of the element increases.1

Trends in Oxidation States

• +4 State: This state is highly stable for lighter elements like carbon and silicon. In these elements, all four valence electrons are typically involved in covalent bonding.213
• +2 State: As the atomic number increases, the $n{s}^2$ electron pair becomes increasingly inert—a phenomenon that allows the $n{p}^2$ electrons to be removed or involved in bonding separately. Consequently, the stability of the +4 state decreases while the +2 state becomes more prominent.12
  • Germanium exhibits a weak +2 state and a strong +4 state.2
  • Tin shows roughly equal stability in both states.2
  • Lead is dominated by the +2 state, with only weak +4 properties.2

While these oxidation states are assigned to covalent compounds, the +2 state can also manifest as actual ionic charges in the heavier members of the family, such as ${\text{Sn}}^{2+}$ and ${\text{Pb}}^{2+}$.1