What type of bonding occurs in a sample of pure chromium, cr? in other words, how is one chromium atom held to another chromium atom?

Chromium is a metal in nature. So when one chromium is bonded to another chromium, there is a weak intermolecular forces which helds them together which we call as "metallic bonding".

Metallic bonding is the intermolecular force of attraction which exist between valence electrons and the metal atoms. It is considered as the sharing of various detached electrons between many positive ions, whereby the electrons serve as a "glue" which gives the substance a definite structure.