Bromine trifluoride autoionizes to form $$\text{BrF}_2^+$$ and $$\text{BrF}_4^-$$. The shapes of the cation and anion are respectively __________, and __________.

Reaction 

$$2BrF_3\longleftrightarrow\ BF_2^{+\ }+BrF_4^-$$

To determine the molecular geometry, we can calculate the steric number (number of bond pairs + lone pairs) for each ion using Valence Shell Electron Pair Repulsion Theory (VSEPR):

$$BrF_2^+$$

• Central atom: $$Br$$
• Valence electrons on $$Br$$ = 7
• Positive charge removes one electron → effectively 6 electrons
• Two $$Br-F$$ bonds + 2 lone pairs on $$Br$$

So, steric number $$=4$$→ tetrahedral electron-pair geometry.

With 2 bond pairs and 2 lone pairs, the molecular shape is:

Bent (V-Shaped)

$$BrF^-_4$$

• $$Br$$ has 7 valence electrons
• One extra electron due to negative charge → 8 electrons
• Four $$Br-F$$ bonds + 2 lone pairs

Steric number $$=6$$ → octahedral electron arrangement.

With 4 bond pairs and 2 lone pairs opposite each other, the shape is:

Square Planar