Qn: Draw the structure and the shape of PCl4 -
If the qn didn't ask for dot and
cross diagram but i draw dot and cross diagram, is it
accepted?
In the A level exams, always be exam-smart : if
you're not sure which answer they want, give both answers. Draw
both the
Kekule structure (what JC
teachers often erroneously call Lewis
structure, and what Cambridge calls Displayed
Structural Formula) as well as the Dot-and-Cross
structure.
In the uninegative (what Cambridge calls
mononegative) PCl4- anion, the uninegative
formal charge is on the central atom P. Since P is
in Group V, it means the P atom has 4 bond pairs and 1 lone
pair (ie. 6 electrons in terms of formal charge and hence a
uninegative formal charge, and 10 electrons in terms of expanded
stable octet).
The electron geometry is trigonal
bipyramidal, and the ionic geometry is
distorted tetrahedron or
see-saw.