In a sample of pure sodium (Na), the type of bonding is metallic bonding. This type of bonding is characterized by the attraction and sharing of valence electrons between metal atoms. In the case of sodium, each atom has one valence electron in its outermost shell, which is loosely held and becomes delocalized (i.e., shared) among all the sodium atoms in the sample.

The delocalized valence electrons form a "sea" of mobile electrons that move freely throughout the entire metal lattice. This sea of electrons creates a strong attractive force that holds the positively charged sodium ions (formed by the loss of the valence electron) together, resulting in a cohesive and stable metallic structure. The delocalized electrons also allow for excellent electrical and thermal conductivity, which are characteristic properties of metals like sodium.