Silver metal crystallises in a cubic closed packed arrangement with edge length 404 pm. Thus, radius of the silver atom is

AB=a,AC=aRadius = r, then BC=CD+DE+EB=r+2r+r=4rFor F.C.C or C.C.P  4r =2ar=24a∴r=a22=40422=4042.828=142.8pmNote: Detailed calculations to relate radius with edge length have been given. Examiner can use direct relation. simple cubic, r=a2; hcp/ccp,r=a22; bcc,r=34a