JEE Main 25 Feb 2021 Shift 1 Solved Paper

According to Molecular Orbital Theory (MOT), electronic configuration and their bond order of given options are as follows
- O22−=σ1s2,σ*1s2,σ2s2,σ*2s2,σ2pz2,π2px2,π2py2,π*2px2,π*2py2
[No. of bonding electrons
Bond order = ‌r=‌

−‌ No. of antibonding electrons] ‌

2

‌‌=‌

10−8

2

=‌

2

2

=1
- He2−=σ1s2,σ*1s2,σ2s1
Bond order =‌

3−2

2

=‌

1

2

=0.5
- Be2=σ1s2,σ*1s2,σ2s2,σ*2s2
Bond order =‌

4−4

2

=0
- He2+=σ1s2,σ*1s1
Bond order =‌

2−1

2

=‌

1

2

=0.5
If bond order of chemical species is zero then that chemical species does not exist. Therefore, Be2 does not exist.