Scientific Tutor

What are the more advanced molecular shapes (molecular geometry)?

Before taking on this section, make sure you have gone over the completing the octet college section. Those molecular shapes and bond angle beyond Tetrahedral (4 bonds – or electron clouds) are the more advanced shapes. They include shapes like triginal bipyrimidal and octahedral but only make sense if you have explored the electron dot structures (Lewis structures) beyond the octet of 8. You identify these molecular shapes and bond angles from their electron dot structures by counting both the atoms bonded to the central atom and the lone pair electrons of the central atom. Use the complete molecular shape (molecular geometry) table below to answer the examples and practice problems.

 

 

Examples: Use the complete molecular shape (molecular geometry) table along with the electron dot structure (Lewis structure) to determine the molecular shape (molecular geometry). VIDEO Molecular Shape from Lewis Structure Examples 2.

 

(pic SF6)

Atoms bonded to central atom: 6

Lone pair electrons of central atom: 0 pairs

Bond Angle of SF₆ (Answer): 90 degrees

Molecular Shape of SF₆ (Answer): OCTEHEDRAL

 

(pic PH5)

Atoms bonded to central atom: 5

Lone pair electrons of central atom: 1 pair (2 electrons total)

Bond Angle of PH₅ (Answer): 90 degrees

Molecular Shape of PH₅ (Answer): SQUARE PYRAMIDAL

 

(pic AsBr3H2)

Atoms bonded to central atom: 5

Lone pair electrons of central atom: 0 pairs

Bond Angle of AsBr₃H₂ (Answer): 90 and 120 degrees

Molecular Shape of AsCl₃H₂ (Answer): TRIGONAL BIPYRIMIDAL

 

(pic BrH3)

Atoms bonded to central atom: 3

Lone pair electrons of central atom: 2 pairs (4 electrons total)

Bond Angle of BrH₃ (Answer): Less than 90 degrees

Molecular Shape of BrH₃ (Answer): T-SHAPED

 

PRACTICE PROBLEMS: Use the electron dot structure (Lewis structure) to determine the molecular shape (molecular geometry).  You might need the complete molecular shape (molecular geometry) table.

 

(pic SeBr₆)

Atoms bonded to central atom: 6

Lone pair electrons of central atom: 0 pairs

Bond Angle of SeBr₆ (Answer): 90 degrees

Molecular Shape of SeBr₆ (Answer): OCTAHEDRAL

 

(PBr₅)

Atoms bonded to central atom: 5

Lone pair electrons of central atom: 0 pairs

Bond Angle of PBr₅ (Answer): 120 and 90 degrees

Molecular Shape of PBr₅ (Answer): TRIGONAL BIPYRAMIDAL

 

(pic KrH₂)

Atoms bonded to central atom: 2

Lone pair electrons of central atom: 3 pair

Bond Angle of KrH₂ (Answer): 180 degrees

Molecular Shape of KrH₂ (Answer): LINEAR

 

(BrH₅)

Atoms bonded to central atom: 5

Lone pair electrons of central atom: 1 pairs

Bond Angle of BrH₅ (Answer): 90 degrees

Molecular Shape of BrH₅ (Answer): SQUARE PYRAMIDAL

 

(KrH₃^1-)

Atoms bonded to central atom: 3

Lone pair electrons of central atom: 3 pair

Bond Angle of KrH₃^1- (Answer): Less than 90 degrees

Molecular Shape KrH₃^1- (Answer): T-SHAPED

 

(XeF₄)

Atoms bonded to central atom: 4

Lone pair electrons of central atom: 2 pairs

Bond Angle of XeF₄ (Answer): 90 degrees

Molecular Shape of XeF₄ (Answer): SQUARE PLANAR