The coordination number of a complex refers to the number of ligands attached to the central metal ion. In this case, the complex is made up of a trivalent actinide, Am III , and six ligands. Therefore, the coordination number is 6.The geometry of a complex depends on the coordination number and the arrangement of the ligands around the central metal ion. For a coordination number of 6, the most common geometry is octahedral. In an octahedral geometry, the six ligands are arranged around the central metal ion with 90-degree angles between them.So, the coordination number of the complex is 6, and its geometry is octahedral.