In the case of the double-bonded O we would have 2 lone pairs of electrons (makes 4) and a further 4 electrons from the double bond. One O is double bonded to the P and the other three Os are single bonded, giving 10 electrons to the P (which it is happy with). We could model this situation by proposing that the P atom exists at the centre, with four O atoms bonded to it. We also have a charge of 3- indicating that we need to take into account 3 additional electrons, giving us 32 electrons overall.
Sigma bond image plus#
This is bonded to four oxygen atoms, which have six valence electrons.įive P electrons plus 4 times 6 O electrons gives 29 electrons. In the phosphate ion we have a central Phosphorus atom, with five valence electrons. Here is how I understand it, armed with the new knowledge contained within the posts above: I'm going to try to synthesise them into a single answer, which I hope will be accurate. Thank you very much, both of you, for some very detailed replies. Phosphate anion is triply negative charged note how there are three oxygens bearing a single negative charge. In addition, the sum of the formal charges on an atom must add up to the overall charge on the atom. The structure shown above is a compromise between number of valence electrons and electronegativity considerations - we wouldn't want a surfeit of electrons around the central phosphorus since that's not as thermodynamically favorable as having the more electronegative oxygen support these electrons. You could draw double bonds for all the oxygens but there aren't that many valence electrons to be distributed. Does this not leave them one electron short?įinally, why are the oxygens shown as carrying a negative charge? With increasing thermodynamic stability they are $$\ce$ double bond.Īpart from the oxygen with a double-bond, we have three oxygensįorming single bonds. There are many different modifications of phosphorus in nature. First of all, let me state the obvious: Phosphorus is awesome.Īfter we got that out of the way we can focus on why.
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