Crystalline solids cubic closest packed

A similar trend exists for the halogens. The structure of crystalline iodine is shown in Figure 13.9. The ratios r2/r for crystalline CI2 (s), Br2 (s), and I2 (s) are 1.68, 1.46, and 1.29, respectively. Although each of the halogens is classified as a nonmetal, the percent metallic character increases down the series. Iodine is the most metallic of the group, a fact that is supported by its grayish color as a solid and its metallic reflectance. In fact, iodine can even adopt a distorted cubic closest-packed structure similar to many metallic solids when it is crystallized at high pressure. 

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