Asf5 Lewis Structure, Geometry:13 Facts You Should Know


AsF5 is an inorganic metalloid halide containing arsenic and five fluorine atoms in which the metalloid is the arsenic atom and the halide is the fluorine atom.

In asf5 Lewis structure Arsenic atom is bonded to five fluorine atoms in a trigonal bipyramidal shape by sharing the five electrons present in its valence shell to each of the five fluorine atoms attaining the sp3d hybridization. They are Lewis’s acid and are non-polar in nature.

Asf5 valence electrons

AsF5 compound has a total of 40 valence electrons in its valence shell (5 from arsenic and 35 valence electrons from five fluorine atoms).

From the periodic table, we can see that Arsenic atom belongs to the p block and comes under the group 15 (pnictogen). We know that from group 13 to 18 the valence electron number will be 10 minus the group number

As for fluorine atom it comes under the group 17th (Halogens)

Valence electrons of arsenic atom = 15- 10 = 5 valence electrons

Valence electrons of fluorine atom =17- 10 = 7 valence electrons

Then the total valence electrons number in AsF5 will be sum of the valence electrons of arsenic and 5 fluorine atoms.

                              5 +(7) 5 =40

The total valence electrons of AsF5 = 40 valence electrons.

Asf5 Lewis structure lone pairs

In AsF5 has no lone pair of electrons because all the 5 valence electrons of Arsenic atom are used to form five single bonds with five fluorine atoms.

The lone pair of an electron is an electron pair not shared with the other atoms in the bond formation.

Out of the 40 valence electrons in AsF5 10 electrons are used for bond formation and the remaining 30 valence electrons does not take part in bond formation. The 30 valence electrons are present in the valence shell of 5 fluorine atoms each taking 6 electrons (3 lone pairs).

So, the total lone pairs present in 5 fluorine atoms will be =30/2 =15 lone pairs

Each lone pair contains 2 electrons.

How to draw Asf5 Lewis structure?

Lewis structure of AsF5 is drawn by using the valence electrons of arsenic and fluorine atoms and following few steps.

Few steps to follow are;

1)Know the total number of valence electrons present in arsenic pentafluoride compound.

Arsenic atom has 5 valence electrons and fluorine atom has 7 valence electrons in its outer shell making the total valence electrons of AsF5 to be 40.

2)Select the central atom and place it at the center and the remaining atoms surrounding it.

The least electronegative atom is selected as the central atom to draw a Lewis structure it is because the least electronegative atom tends to share more of its electrons to the surrounding atoms

 We know that the fluorine atom is considered the most electronegative atom. So, in AsF5 Arsenic atom is considered the central atom the 5 fluorine atoms are placed around the central atom arsenic.

3)The central atom and its surroundings undergo a chemical combination by pairing its valence electrons, forming a single (sigma) bond.

The 5 valence electrons of arsenic atoms pair with each electron of 5 fluorine atoms, and a single bond is formed.

Thus, 10 valence electrons take part in bond formation i.e. 5 from arsenic and 1 each from 5 fluorine atoms. So, there are 10 bonding electrons (5 bond pairs) and 30 non-bonded (15 lone pairs) electrons in AsF5.

4)In order to complete the remaining valence, electrons should be placed around the surrounding atoms.

The 5 valence electrons of arsenic atoms are used up, so the remaining 30 electrons belong to 5 fluorine atoms, and each fluorine atom requires 8 electrons to complete its octet.

The total number of non-bonded electrons present = 30

Number of surrounding atoms (Fluorine) present = 5

So, the number of atoms required by each surrounding atom =30/5 =6

Each 6 electrons are shared between the 5 fluorine atoms from 30 electrons and thus, each fluorine atom completes its octet (6 electrons from non-bonded electrons and 2 electrons from single bond with arsenic atom).

An arsenic atom will have a total of 10 electrons after bond formation (5 electrons from its valence shell and the other 5 electrons from 5 fluorine atoms shared during bond formation).

These are the steps to be followed, and that is how the AsF5 Lewis structure is drawn.

Read more about Strong Electrolyte Examples

Asf5 Lewis structure octet rule

AsF5 Lewis structure does not obey the octet rule because the arsenic atom has more than 8 electrons in its valence shell.

According to the octet rule, the atoms of various elements enter into chemical combinations in order to attain the eight-electron configuration in their outermost shell.

In AsF5 compound, Arsenic atom has a total of 10 electrons in its valence shell (arsenic forms 5 single bonds with 5 fluorine atoms) and more than 8 electrons with the expanded octet.

The reason is because the arsenic atom has a principal quantum number n = 4. Therefore, it has an empty 4d orbital in its shell which can take part in hybridization and thus  have an expanded octet.

Asf5 Lewis structure formal charge

The formal charge of arsenic atom and the 5 fluorine atoms in Arsenic Pentafluoride Lewis structure is zero.

Formal charge on an atom in a Lewis structure = total number of valence electrons in the free atom -the total number of non-bonding (lone pair) electrons -half the total number of bonding electrons.

Formal charge on Arsenic atom

Total number of valence electrons in Arsenic atom = 5

Total number of non-bonding electrons in Arsenic = 0

Total number of bonding electrons in Arsenic atom =10

 Formal charge = 5-0-10/2 =5-5 =0

Therefore, the formal charge of arsenic atom is = 0

Formal charge on fluorine atom

Total number of valence electrons in fluorine atom = 7

Total number of non-bonding electrons in fluorine = 6

Total number of bonding electrons in fluorine atom =2

 Formal charge = 7-6-2/2 =7-6-1 =0

Therefore, the formal charge of fluorine atom is = 0

Thus, the total formal charge of the atoms in AsF5 will be = 0

Asf5 Lewis structure resonance

AsF5 Lewis structure does not show resonance

Resonance is the movement of pi electrons or lone pair of electrons that are conjugated to the pi bonds within the compounds.

The reason for Arsenic Pentafluoride Lewis structure to not exhibit resonance is because it does not have pi electrons in its structure to resonate and also the lone pair electrons present in the fluorine atom does not take part in resonance.

Asf5 Lewis structure shape

AsF5 Lewis structure has trigonal bipyramidal shape containing 5 bond pair of electrons and 15 non-bonding (lone pair) pair of electrons.

Trigonal bipyramidal shape of AsF5

The shape of the AsF5 Lewis structure is determined according to the VSEPR theory. The central atom arsenic shares its 5 valence electrons with the 5 fluorine atoms. The 2 fluorine atoms are present in the axial position and 3 fluorine atoms are in the equatorial position.

Asf5 Lewis structure angle

AsF5 Lewis structure forms 2 bond angles 120o and 90o degree having trigonal bipyramidal geometry.

AsF5 bond angle

In AsF5 structure 3 fluorine atoms are present in the equatorial position and the bond angle formed between the 3 fluorine atom is 120o. The bond angle formed between the remaining 2 fluorine atoms present in the axial position is 90o.

Asf5 hybridization

AsF5 molecule has sp3d hybridisation.

The electronic configuration of As is [Ar] 3d10 4s2 4p3.

Electronic configuration box diagram of AsF5

Thus, AsF5 acquire sp3d hybridisation and have trigonal bipyramidal geometry.

Asf5 solubility

AsF5 is soluble in benzene, ethanol, dimethyl ether. They are easily hydrolysed by water and humid air to form arsenic and hydrogen fluoride. It forms white clouds in moist air.

Is Asf5 acidic or basic?

It is a strong Lewis acid fluoride. They act as a strong fluorine ion acceptor.

When arsenic pentafluoride reacts with Sulphur tetrafluoride, it readily accepts fluorine and becomes AsF6.

AsF5 +SF4 –> SF3 +SF6

Is Asf5 ionic?

AsF5 is a monomeric covalent compound.

The bond formed between the arsenic and 5 fluorine atoms is by sharing of electrons and not by the transferring of electrons completely between the atoms.

Is Asf5 polar or nonpolar?

Arsenic Pentafluoride is a non-polar compound.

According to the Pauling scale it should be polar because of the electronegativity difference between As and F atom.

 But the compound has a symmetrical geometry due to its triagonal bipyramidal structure, the charge induced by all As-F bond will be cancelled out making the net dipole moment to become zero.

Conclusion

Lewis structure of AsF5 helped us to study about its geometry, formal charge, hybridization, bond angle and its polarity and some other facts related to it.

Lina Karankal

Hi..I am Lina Karankal, I have completed my Master's in Chemistry. I always like to explore new areas in the field of Chemistry. Apart from this, I like to read, travel and listen to Music.

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