# The co-ordination number of metal crystallizing in a structure adopting hexagonal close packing is

$(a)\;12\qquad(b)\;6\qquad(c)\;8\qquad(d)\;4$

In three dimensional hexagonal close packing of crystals, the two dimensional hcp layers are arranged in ABAB...... pattern as shown below.
The atoms in A layers are exactly above one type of the trigonal voids in B layer.
The central atom in B layer is immediately surrounded by 12 atoms .
6 in layer B and 3 each in two A layers .
edited Oct 23, 2017 by meena.p