Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), with an electron configuration in the outermost shells atypical for group 5. (This can be observed in the neighborhood of ruthenium (44), rhodium (45), and palladium (46). However, it is thought to have a body-centered cubic crystal structure from T = 0 K to its melting point. High-resolution measurements of the thermal expansion along the three crystallographic axes reveal anisotropies inconsistent with a cubic structure. Therefore, further research in this area is expected.