For MgSe, which crstallize structure un the rock salt structure, the unit cell edge is 5.45A. Determine the internuclear distance between neighboring Mg2+ and Se2-, as well as the cation and anion radii.

To determine the internuclear distance between neighboring Mg2+ and Se2- ions, as well as the cation and anion radii, we need to understand the crystal structure of MgSe and its unit cell.

The rock salt structure is a commonly observed structure for ionic compounds, where cations occupy the corners of a face-centered cubic (FCC) unit cell and anions occupy the center of each face. In MgSe, Mg2+ ions are cations, while Se2- ions are anions.

In the rock salt structure, the distance between the neighboring cation and anion is equal to the diagonal of a face of the unit cell. With an FCC structure, the diagonal can be calculated using the unit cell edge length (a):

Diagonal = √2*a

Given that the unit cell edge for MgSe is 5.45Å, we can calculate the interatomic distance between neighboring Mg2+ and Se2- ions:

Diagonal = √2 * 5.45Å
= √(2 * 5.45 * 5.45)
= 7.692Å

Therefore, the internuclear distance between neighboring Mg2+ and Se2- ions in MgSe is approximately 7.692Å.

To determine the cation and anion radii, we can divide the unit cell edge length by 2. This is because the radius of each ion is half the distance between neighboring cations or anions along the same face.

Cation radius = Anion radius = a / 2

Cation radius = Anion radius = 5.45Å / 2
= 2.725Å

Therefore, the cation and anion radii in MgSe are approximately 2.725Å.