Br^(-) ions form close packed structure. If the radius of Br^(-) ion is 195 p, calculate the radius of the cation that just fits in the tetrahedral hole. Can a cation A^(+) having a radius of 82 pm be slipped into the octahedral hole of the crystal A^(+) Br^(-)?

Br^(-) ions form close packed structure. If the radius of Br^(-) ion i

1.	Br^(-) ions form close packed structure. If the radius of Br^(-) ion is 195 p, calculate the radius of the cation that just fits in the tetrahedral hole. Can a cation A^(+) having a radius of 82 pm be slipped into the octahedral hole of the crystal A^(+) Br^(-)?
Answer» Solution :(i) For a TETRAHEDRAL hole, `(R^(+))/(r^(-))= 0.225` `r^(+)` or radius of tetrahedral hole = `0.225 XX r^(-)=0.225 xx 195=43.875` pm Thus, a cation having radius 43.875 pm will just fit in the tetrahedral hole. (ii) For an OCTAHEDRAL hole, `(r^(+))/(r^(-))= 0.414` , `r^(-) = 195` pm `r^+` or radius of octahedral hole = `0.414 xx r^(-)=0.414 xx 195` pm=80.73 pm Therefore, cation having radius of 82 pm cannot be slipped into an octahedral hole of 80.73 pm.