Everything Science Grade 11

CHAPTER 1. ATOMICCOMBINATIONS 1.10

1. Copy and complete the table below:

Compound Cation Anion Formula

Na+ Cl−

potassium bromide Br−

NH+ 4 Cl−

potassium chromate

PbI

potassium permanganate

calcium phosphate

2. Write the chemical formula for each of the following compounds:

(a) hydrogen cyanide

(b) carbon dioxide

(c) sodium carbonate

(d) ammonium hydroxide

(e) barium sulphate

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1.10 The Shape of Molecules

Valence Shell Electron Pair Repulsion

(VSEPR) theory

ESBU

The shape of a covalent molecule can be predicted using the ValenceShell Electron Pair Repulsion
(VSEPR) theory. This isa model in chemistry that tries to predict theshapes of molecules. Very
simply, VSEPR theory says that the valence electron pairs in a molecule will arrange themselves around
the central atom of themolecule so that the repulsion between their negative charges is as small as
possible. In other words, the valence electronpairs arrange themselves so that they are as farapart
as they can be. The number of valence electron pairs in the moleculedetermines the shape of that
molecule.

DEFINITION: Valence Shell Electron Pair Repulsion Theory

Valence shell electron pair repulsion (VSEPR) theory is a model in chemistry, which

is used to predict the shape of individual molecules, based upon the extent of their

electron-pair repulsion.