Arsenate Ion (AsO43-) - Lewis Structure
In the lewis structure of Arsenate ion (AsO43-), there are three As-O bonds and one As=O bond. Arsenic atom is located as the center atom and there are five bonds around arsenic atom. Three oxygen atoms have 3 lone pairs and arsenic atom does not have lone pairs. We will learn how to draw the lewis structure of AsO4 3- step by step in this tutorial.
AsO43- lewis structure
Figure of AsO43- lewis structure is given above and you can see how atoms are joint with other atoms. Three oxygen atoms have -1 ion and overall charge of ion is -3.
Steps of drawing lewis structure of AsO43-
There are several steps to draw the lewis structure of the AsO43-. Each step is explained in detail in the remaining part of this tutorial.
- Find total number of electrons of the valance shells of Arsenic and Oxygen atoms
- Determine total electrons pairs as lone pairs and bonds
- Find center atom and basic sketch
- Mark lone pairs on atoms
- Mark charges on atoms if there are charges.
- Check the stability and minimize charges on atoms by converting lone pairs to bonds to obtain best lewis structure.
Total number of electrons of the valance shells of AsO43-
There are only two elements in AsO43- molecule; Arsenic and Oxygen. Arsenic is a group VA element and has only five electrons in its valence shell. Oxygen is a group VIA element in the periodic table and contains six electrons in its last shell. Arsenic atom has five electrons in its last shell because it is a VA group element. Now we know how many electrons includes in valence shells of each atom.
- valence electrons given by Arsenic atom = 5 * 1 = 5
- valence electrons given by oxygen atoms = 6 * 4 = 24
- Due to overall charge of -3, three more electron should be added to total number of valence electrons.
- Total valence electrons = 5 + 24 + 3 = 32
Total valence electrons pairs of AsO43-
Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells
Total electron pairs are determined by dividing the number total valence electrons by two. For, AsO43-<, total pairs of electrons are sixteen (32/2) in their valence shells.
Selection of center atom and skeletal of AsO43-
To be the center atom, ability of having greater valance and being most electropositive element in the molecule are important facts. These are not essential. But those two facts play a major role in selecting center atom of a molecule or ion in a covalent compound.
However, AsO43- ion is not a simple ion, we should check those facts. Arsenic atom has the more chance to be the center atom than oxygen atom because Arsenic can show maximum valence of 5 while oxygen's maximum valence is 2.
And also, Arsenic is more electropositive element than Oxygen.
Determine lone pairs on atoms
After deciding the center atom and skeletal of AsO43- ion, we mark lone pairs on atoms. Remember that, there are total of sixteen electron pairs to mark on atoms as bonds and lone pairs.
- There are already four bonds in the above drawn skeletal. Now only twelve (16-4) electron pairs are remaining to mark on atoms.
- Usually, those remaining electron pairs should be started to mark on outside atoms (on oxygen atoms, in this case). Therefore, mark electrons pairs on oxygen atoms; Each oxygen atom will take three lone pairs. Now, twelve electron pairs are marked on all four Oxygen atoms.
- Now, all remained electron pairs (12) are marked on Oxygen atoms and no more electron pairs to mark on Arsenic atom.
Mark charges on atoms and check the stability and minimize charges on atoms by converting lone pairs to bonds
There are charges on Arsenic and Oxygen atoms.
Because all atoms have charges, this structure is not stable. Therefore, we are going to convert a lone pair if Oxygen atom to make a bond with Arsenic atom. Then, there will be a double bond between Arsenic atom and one Oxygen atom.
Now, you see Arsenic atom and one oxygen atom do not have charges furthermore. It means, this structure is much stable than previous structure.
Questions