Which theory predicts the shapes of molecules and polyatomic ions?
Valence shell electron pair repulsion
How does Valence shell electron pair repulsion (VSEPR) theory work?
Shapes can be predicted from the number of bonding electron pairs and the number of non-bonding electron pairs.
How is the total of electron pairs calculated?
Electron pairs = (number of electrons on centre + number of bonded atoms)/2.
5 outer electrons on the central nitrogen atom (electron arrangement 2, 5) + 3 hydrogen atoms bonded.
5+3=(8)/2 = 4 (3 bonded and 1 lone pair)
What arrangement of electron pairs would be found when the total number of electron pairs is 2, 3, 4, 5 and 6, respectively.
linear, trigonal (trigonal planar), tetrahedral, trigonal bipyramidal and octahedral
What arrangement of electron pairs would be found where we have:
i) 3 total electron pairs but 2 bonding pairs
ii) 4 total electron pairs but 3 bonding pairs
iii) 6 total electron pairs but 5 bonding pairs
ii) Trigonal Pyramid
iii) Square pyramid
Electron pairs will repel each other. They can be bonded or non-bonding (lone) pairs.
What is the order of repulsive effect?
non-bonded pair:non-bonded pair > non-bonded pair:bonded pair > bonded pair: bonded pair
What effect do lone pairs have of the positions of bonded pairs?
They distort the shape.
What shape would Beryllium dichloride take?
What shape would hydrogen oxide take?
What shape would Boron trifluoride take?