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In this example, PO43-, the Lewis diagram
shows phosphorus at the center with no lone electron pairs. The
phosphorus and and one oxygen are bonded through a double bond
which counts as "one electron pair". Hence the molecule
has four electron pairs and is tetrahedral.
The Lewis diagram is as follows:
P = 5 e-
O = 6e- x 4 = 24e-
3- charge = 3e-
Total electrons = 32
Phosphorus is an atom that may exceed an octet of electrons.
Phosphates are found in certain types of rocks, which are
mined and converted to fertilizer. Plants need phosphate to grow
as it is incorporated in the DNA and RNA genetic molecules. Furthermore
phosphate is an important structural component of bones and teeth.