Bond order of which among the following molecules is zero ?

Options

A. `F_(2)`
B. `O_(2)`
C. `Be_(2)`
D. `Li_(2)`

Answer

C

Explanation

(a) `F_(2)` molecule
`sigma 1 s^(2) , sigma^(**) 1 s^(2) , sigma 2s^(2) , sigma ^(**) 2 s^(2) , sigma^(**) 2s^(2) , sigma 2p_(z) ^(2) , pi 2p_(x)^(2) = pi 2p_(y)^(2) , pi^** 2p_(x)^(2) = pi^(**) 2p_(y)^(2)`
Bond order = `(1)/(2) (N_(b) - N_(a)) = (1)/(2) (10 - 8) = 1`
`(b) O_(2)` molecule
`= sigma 1s^(2) , sigma^(**) 1 s^(2) , sigma 2s^(2) , sigma^(**) 2s^(2) , sigma 2p_(z)^(2) , pi 2p_(x)^(2) , pi^(**) 2p_(x)^(1) = pi^(**) 2p_(y)'`
Bond order = `(1)/(2) (10 - 6) = 2`
(c) `Be_(2)` molecule
`= sigma 1 s^(2) , sigma^(**) 1 s^(2) , sigma 2 s^(2) , sigma^(**) 2s^(2)`
Bond = `(1)/(2) (4- 4) = 0 `
(d) `Li_(2)` molecule = `sigma 1s^(2) , sigma^(**) 1 s^(2) sigma 2 s^(2)`
Bond order = `(1)/(2 ( 4 - 2) = 1`
Therefore , `Be_(2)` molecule has zero bond order