Final answer:
Atoms form bonds by sharing unpaired valence electrons. The number of bonds without hybridization equals the number of unpaired valence electrons in an atom's ground state. Hybridization allows atoms to form additional bonds by mixing orbitals and promoting electrons.
Step-by-step explanation:
The valence electron configuration of an atom dictates how many bonds it can form. When atoms bond, they share valence electrons, and the number of bonds an atom can make depends on the number of unpaired electrons in its valence shell. Without hybridization, an atom can only form as many bonds as it has unpaired electrons available for bonding.
Hybridization is a concept in chemistry used to describe the change in energy and orientation of atomic orbitals to maximize the overlap between valence electrons of different atoms, typically leading to the formation of more bonds than the atoms' ground state configurations would allow. For example, in beryllium hydride (BeH2), the ground state electron configuration of beryllium is 1s22s2, with no unpaired electrons in the valence shell. Yet, the molecule forms two bonds via hybridization.
Beryllium undergoes sp hybridization, where one of the 2s electrons is promoted to an empty 2p orbital. This allows for the creation of two equivalent sp hybrid orbitals, both singly occupied. These hybrid orbitals form bonds with the hydrogen atoms in BeH2, making a linear molecule as predicted by the VSEPR model.