# Why do elements in the same group have a similar reactivity?

The valence shell of the carbon atom ($Z = 6$) is described as $2 {s}^{2} 2 {p}^{2}$; that of silicon ($Z = 14$), $3 {s}^{2} 3 {p}^{2}$. Given this electronic configuration, where the silicon atoms have orbitals of precisely the same symmetry as does carbon, we might expect that the chemistry of silicon and carbon would be similar, and we would be right.