Phosphorus pentachloride (PCl5) contains five chlorine atoms and one phosphorus atom. In PCl5 lewis structure, each chlorine atom is joint with center phosphorus atom through a single bond (sigma bond). You can see there is no lone pairs on phosphorus atom in PCl5 as PCl3. In this tutorial, we will learn how to draw the lewis structure of PCl5 step by step with all theories.
In this lewis structure of PCl5, center phosphorus atom has made five single bonds with five chlorine atoms. There is a lone pair on center phosphorus atom and each chlorine atom also has three lone pairs. That means, there are ten electrons around phosphorus atom. This an example where some elements can keep more than eight electrons in their valence shell. Also, there are no charges on atoms in PCl5 lewis structure.
There are guidelines to draw a lewis structure properly and easily. Number of steps can be changed according the complexity of the molecule or ion. Now, we are going to study each step of drawing the lewis structure of PCl5 in next sections.
There are only two elements in phosphorus trichloride; phosphorus and chlorine. Phosphorus is a group VA element in the periodic table and has five electrons in its last shell (valence shell). Chlorine is a group VIIA element in the periodic table and contains seven electrons in its last shell.
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, PCl3, Total pairs of electrons are twenty (40/2) in their valence shells.
When you draw a lewis structure, selecting the center atom is very important because structure of the molecule depend on the center atom selection. There are requirements to be the center atom. Having a high valence and being the most electropositive atom are the most important facts to be a center atom. In PCl5, there are only two elements to select the center atom. But, selecting the center atom is a challenging thing for PCl5. But, we are going to understand that now.
After determining the center atom and sketch of PCl5 molecule, we should start to mark lone pairs on atoms. Remember that, there are total of 20 electron pairs to mark as bonds and lone pairs in overall molecule.
There are no charges on any of atoms. Therefore, we don't need to worry about reducing charges to get the most stable lewis structure. That means, we have already obtained the lewis structure of PCl5 after marking lone pairs on our sketch.
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