Question

What is the "AXE" description of the fluoroform CHF3 molecule?

Answer 1

Arriving at AXE description of any molecule is very simple. It is mostly used when we work with VSEPR theory. There is an AXE description or notation for each geometry because it mainly centres around the geometry of a molecule.

A - indicates the central atom

X - indicates the atoms attached to the central atom and the number of atoms attached to the central atom is denoted as a subscript to X.

E - indicates the number of lone pairs on the central atom

For example - CH₄.

Central atom is carbon , C and 4 H are attached to it and it is a stable molecule with 8 electrons that is octet configuration and hence no lonepairs on C. It is an example of a tetrahedral molecule. So all molecules with tetrahedral geometry has AXE notation as AX_4.

Now CHF₃ is also a molecule with tetrahedral geometry so without a doubt it also has a notation of AX_4.

Examples,

BF₃ - has 3 electrons in its outer shell - all 3 are shared with F- so no lonepair left - hence AX₃ - BF₃ has a triagonal planar geometry hence all molecules with a triagonal planar geometry will be AX_3.

Now lets consider PCl₃ - has 5 electrons in its outer shell as it belongs to the nitrogen family - 3 electrons are shared with Cl (chlorine) - 2 electrons are non bonded or free hence it is a lone pair - so the AXE notation is AX₃E_1.

Answer 2

it is ax4e0, aleks told it thats what it is.