Na2SeO5 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a distorted rectangular see-saw-like geometry to four equivalent O(2) atoms. Se(1) is bonded in a distorted square pyramidal geometry to one O(1) and four equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one Se(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Se(1), and one O(2) atom.
Na2SeO5 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(2) atoms. Both Na(1)-O(1) bond lengths are 2.10 Å. All Na(1)-O(2) bond lengths are 2.57 Å. In the second Na site, Na(2) is bonded in a distorted rectangular see-saw-like geometry to four equivalent O(2) atoms. All Na(2)-O(2) bond lengths are 2.36 Å. Se(1) is bonded in a distorted square pyramidal geometry to one O(1) and four equivalent O(2) atoms. The Se(1)-O(1) bond length is 1.67 Å. All Se(1)-O(2) bond lengths are 2.13 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one Se(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Se(1), and one O(2) atom. The O(2)-O(2) bond length is 1.47 Å.