Sodium metal crystallises in a body centred cubic lattice with edge length of the unit cell equal to `4.29Å` The radius of the sodium atom is approximately

Options

A. `5.72 Å`
B. `0.93Å`
C. `1.86Å`
D. `3.22 Å`

Answer

C

Explanation

In bcc the atoms touch along diagonal
` therefore 2 r + 2 r = sqrt 3 a `
` therefore r = ( sqrt 3 a ) /( 4 ) = ( sqrt 3 xx 4.29 ) /( 4 ) = 1.857 Å`