Question

When amorphous red phosphorus is heated at high
pressure, it is transformed into the allotrope black
phosphorus, which can exist in one of several forms.
One form consists of six-membered rings of phosphorus
atoms (Figure P12.71a). Why are the six-atom rings in
black phosphorus puckered, whereas the six-atom rings in
graphite (Figure P12.71b) are planar?

hee Fnnces1 Allotropes of Carbon Concept Review 12.71. When amorphous red phosphorus is heated at high pressure, it is transformed into the allotrope black phosphorus, which can exist in one of several forms. One form consists of six-membered rings of phosphorus atoms (Figure P12.71a) Why are the six-atom rings in black phosphorus packered, whereas the six-atom rings in graphite (Figure P12.71b) are planar? 102 )Black phosphons FIGURE P12 71 )Graphite 22 16be cahon.atoms.in.hineammscndbals oe hee to sear

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Answer 1

Carbon has four valence electrons. In graphite, each carbon atom is bonded to three other carbon atoms and each atom has a free electron. So, the hybridization is sp2 which leads to the planar structure.

Phosphorus has five valence electrons. So, in order to bond with three other phosphorus atoms and also having a lone pair, four hybridizated orbitals are required. So, the hybridization is sp3 which leads to the puckered structure.

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