Vitamin B-12 doesn't have a single chemical formula like simple molecules. It's a complex compound with different forms, all containing a cobalt atom at their core. The most common form is cyanocobalamin, but other forms include hydroxocobalamin, methylcobalamin, and adenosylcobalamin.

Here's a simplified representation of the structure, highlighting the key features:

* Cobalt (Co) atom: Located at the center of the molecule.

* Corrin ring: A complex ring structure made of four pyrrole rings linked together.

* Side chains: Different functional groups attached to the corrin ring.

Here's the chemical formula for cyanocobalamin, the most common form:

C63H88CoN14O14P

However, this doesn't capture the complexity of the molecule. The specific arrangement of atoms and functional groups within the corrin ring and its side chains determines the specific form of vitamin B-12 and its biological function.

It's important to note: While the chemical formula is useful, understanding the biological roles and different forms of vitamin B-12 requires more than just looking at the formula. It's a fascinating and complex molecule!