Everything Science Grade 11

1.5 CHAPTER 1. ATOMICCOMBINATIONS

3. Draw simple diagrams to show how electronsare arranged in the following covalent molecules:

(a) Water (H 2 O)

(b) Chlorine (Cl 2 )

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(1.) 01h3 (2.) 01h4 (3.) 01h5

1.5 Lewis notation andmolecular structure

ESBF

Although we have useddiagrams to show the structure of molecules, there are other forms of notation

that can be used, such as Lewis notation and Couper notation. Lewis notation uses dots and crosses

to represent the valence electrons on different atoms. Thechemical symbol of theelement is used to

represent the nucleus and the core electrons of the atom.

So, for example, a hydrogen atom would be represented like this:

H •

A chlorine atom wouldlook like this:

Cl

××

××

××

×

A molecule of hydrogenchloride would be shown like this:

Cl

××

××

××

ו

H

The dot and cross in between the two atoms, represent the pair of electrons that are shared in the

covalent bond.

Example 4: Lewis notation: Simplemolecules

QUESTION

Represent the moleculeH 2 O using Lewis notation

SOLUTION

Step 1 : For each atom, determine the number of valence electrons in the atom, and

represent these using dots and crosses.