Final answer:
Hypervalent molecules, also known as expanded octet molecules, are formed from elements that have more than four valence orbitals. They share more than four pairs of electrons, resulting in a central atom with more electrons than needed for a noble gas configuration. Examples include phosphorous pentachloride (PCl5) and sulfur hexafluoride (SF6).
Step-by-step explanation:
Hypervalent molecules, also known as expanded octet molecules, are formed from elements in the third and higher periods of the periodic table that have more than four valence orbitals. This allows them to share more than four pairs of electrons with other atoms, resulting in a central atom with more electrons than needed for a noble gas configuration.
For example, phosphorous pentachloride (PCl5) shares five pairs of electrons, resulting in a total of ten electrons in the valence shell. Another example is sulfur hexafluoride (SF6). In some hypervalent molecules, such as IF5 and XeF4, some of the electrons in the outer shell of the central atom are lone pairs.