Describe the electronic structure using molecular orbital theory, calculate the bond order of each and decide whether it should be stable. For each state whether the substance is diamagnetic or paramagnetic. (Enter the bond order to 1 decimal place.)
(a) B2
KK(σ2s)2(σ2s*)2(π2p)2
KK(σ2s)2(σ2s*)1(π2p)2
KK(σ2s)2(σ2s*)2(π2p)1
KK(σ2s)2(π2s*)2(π2p)2
bond order------------
-----------stability
stable or unstable
magnetic character
paramagnetic diamagnetic
(b) B2+
KK(π2s)2(σ2s*)2(π2p)1
KK(σ2s)2(σ2s*)2(π2p)1
KK(σ2s)2(σ2s*)1(π2p)1
KK(σ2s)2(σ2s*)2(π2p)2
bond order---------
------------stability
stable unstable
magnetic character
paramagnetic diamagnetic
(c) O2−
KK(σ2s)2(σ2s*)2(π2p)4(σ2p)2(σ2p*)3
KK(σ2s)2(σ2s*)2(π2p)4(σ2p)2(π2p*)3
KK(σ2s)2(σ2s*)2(π2p)4(σ2p)2(π2p*)1
KK(σ2s)2(σ2s*)2(π2p)4(σ2p)2(π2p*)2
bond order---------
----------stability
stable unstable
magnetic character
paramagnetic diamagnetic
(a) B2
The MO configuration is : KK(σ2s)2(σ2s*)2(π2p)2
Bond order = (1/2) [number of electrons in bonding orbital - number of electrons in anti-bonding orbital)
= (1/2) [4-2]
= 1.0
Since there are unpaired electrons in π2p(π2px1 π2py1) it is paramagnetic
(b) B2+
The MO configuration is : KK(σ2s)2(σ2s*)2(π2p)1
Bond order = (1/2) [number of electrons in bonding orbital - number of electrons in anti-bonding orbital)
= (1/2) [3-2]
= 0.5
Since there are unpaired electrons in π2p(π2px1 π2py1) it is paramagnetic
(c) O2-
The MO configuration is : KK(σ2s)2(σ2s*)2(π2p)4(σ2p)2(π2p*)3
Bond order = (1/2) [number of electrons in bonding orbital - number of electrons in anti-bonding orbital)
= (1/2) [8-5]
= 1.5
Since there are unpaired electrons in π*2p(π*2px1 π*2py1) it is paramagnetic
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