In this post, we will be drawing the Lewis structure, and determining the geometry and hybridization of AsF_{5}.

**AsF**_{5} Lewis Structure

_{5}Lewis Structure

The first thing we need to do when drawing a Lewis structure is determine the total number of valence electrons in the molecule. Remember, **valence electrons** are those in the **outermost principal energy level**. For example: Na – 1s^{2}2s^{2}2p^{6}3s^{1}, Cl – 1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}

The number of valence electrons, for main group elements, corresponds to their **group number** in the periodic table:

For **d block** elements, the outermost **d electrons are also counted** as valence electrons (ns + (n-1)d). For example, iron has eight valence electrons: Fe – 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{6}.

Arsenic is the central atom:

Arsenic is in group 5, so it has five valence electrons, while chlorine, being in group 7, has seven valence electrons. Therefore, there are, in total, 5×7 + 5 = 40 electrons, out of which, 10 are used to make 5 covalent bonds. All the remaining 30 are divided between the five fluorine atoms, each taking 6 electrons as 3 lone pairs:

There are 5 atoms and no lone pairs on the central atom, therefore, **both geometries are trigonal bipyramidal**:

_{}

**AsF**_{5} Hybridization

_{5}Hybridization

The steric number of arsenic is 5 – five atoms, with no lone pairs, and therefore, the hybridization is *sp*^{3}*d*.

Check this 99-question multiple-choice quiz on Geometry and Hybridization:

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