Boron shows some anomalous properties in the respective group to which it belongs, in these anomalous properties they resemble the second elements of the succeeding group. Thus boron and silicon shows similarities in their properties this develops diagonal relationship between them.

1. Boron is a nonmetal while other member are metals.
2. Boron shows allotropy while other member do not.
3. Amongest the elements of group 13, boron has highest melting and boiling point.
4. Boron hydride is quite stable.

1. In diborane, each boron atom has three valence electrons for sharing. X-diffraction studies shows that, there are two types hydrogen atoms in boron structure, called as terminal hydrogen. 
2. Bonding diagram of diborane $(B_2{H}_6)$ showing with curved lines a pair of three-center two-electron bonds, each of which consists of a pair of electrons bonding three atoms, two boron atoms and a hydrogen atom in the middle.
3. Diborane adopts a $D_{2}H$ structure containing four terminal and two bridging hydrogen atoms.

Carbon because of the absence of d-orbitals, cannot expand its valency and hence, its maximum covalency or coordination number is four. But other member show coordination greater than 4 forming penta-coordinated and hexa-coordinated complexes.

1. Buckminster Fullerene is one type of fullerene. Fullerenes are made from carbon atoms joined together to make balls, cages or tubes of carbon. The molecules of Buckminster Fullerene are spherical and are also known as 'buckyballs' formula C60.
Buckminster Fullerene is a black solid although it's deep red when in solution in petrol. The tube fullerenes are called nanotubes which are very strong.
2. Diamond is another allotrpic form of carbon in which carbon is tetrahedrally arranged and it is shiny, lustrous , and non conductor of heat and electricity.
3. Graphite is an alotrope of carbon in which carbon atoms are hexagon-ally placed to form network structure.It is blackish , slippery and conductor of heat and electricity.

1.Orthosilicates. These are simple silicates containing discrete $Si{O}_4^{-}4$ tetrahedra.
2.Pyrosilicates. When two $Si{O}_4^{-}4$ tetrahedra share one corner, $S{i}_2{O}_7^{-}6$ anion is formed. Silicates containing this anion are called pyrosilicates.
3.Cyclic or Ring. If two oxygen atoms per tetrahedron are shared to form closed rings such that structures contain anion, this structure is called as cyclic or ring.
4.Chain silicates. If two oxygen atoms per tetrahedron are shared such that a linear single strand chain is formed then structure is called as chain silicates.
5.Sheet silicates.The sharing of three corners result in an infinite two dimensional sheet,such structures are called as sheet silicates.
6.Three-dimensional silicates. If all the four corners are shared with other tetrahedra, three-dimensional network structure is obtained.