Final answer:
The pair consisting of only network solids is diamond and graphite, both of which are forms of carbon and represent different types of covalent network solids with extensive covalent bonding throughout their structures.
Step-by-step explanation:
The pair consisting of only network solids is diamond and graphite. Both diamond and graphite are allotropes of carbon and represent different forms of covalent network solids. In diamond, each carbon atom is sp3 hybridized and forms four single covalent bonds in a tetrahedral geometry, creating a rigid three-dimensional structure. This makes diamond an extremely hard material with high melting point, surpassing 3,500°C, due to the strong covalent bonds that extend throughout the entire crystal. On the other hand, graphite consists of layers of carbon atoms arranged in six-membered rings.
Each carbon atom is sp2 hybridized and bonded to three other carbon atoms in a planar structure with a fourth electron that is free to move along the layers, allowing graphite to conduct electricity. The layers in graphite are held together by weaker van der Waals forces, making it softer than diamond. Both diamond and graphite have extensive networks of covalent bonds, making them network solids.