In a lab experiment, students had four samples of elements. They made observations about the appearance of each sample, then proceeded to conduct three separate experiments. In the first, they found the melting point of each by holding small samples in a Bunsen burner with a temperature probe. In the second, they held a conductivity probe to two separate sections of the sample. In the final test, they took a small sample and hit it with a hammer. Which element is LEAST likely to be metallic?