Here eight 90∘ angles between bond pair and bond pair. Those angles are ∠1M2,∠2M3,∠3M4,∠4M1,∠5M1,∠5M2,∠5M3,∠5M4
Here twelve 90∘ angles between bond pair and bond pair. Those angles are ∠1M2,∠2M3,∠3M4,∠4M1,∠5M1,∠5M2,∠5M3,∠5M4,∠6M1,∠6M2,∠6M3,∠6M4
Here four 90∘ angles between bond pair and bond pair. Those angles are ∠1M2,∠2M3,∠3M4,∠4M1 .
Here six 90∘ angles between bond pair and bond pair. Those angles are ∠1M3,∠1M4,∠1M5,∠2M3,∠2M4,∠2M5 .