Everything Science Grade 10

CHAPTER 6. CHEMICAL BONDING 6.2

For carbon dioxide, you can see how we represent a double bond in Lewis notation. As
there are two bonds between each oxygen atom and the carbon atom, two pairs of valence
electrons link them. Similarly, hydrogen cyanide shows how to represent a triple bond.

Exercise 6 - 1

1. Represent each of the followingatomsusing Lewis notation:

a. beryllium

b. calcium

c. lithium

2. Represent each of the followingmoleculesusing Lewis notation:

a. bromine gas (Br 2 )

b. carbon dioxide (CO 2 )

Which of these two molecules contains a double bond?

3. Two chemical reactions are described below.

• nitrogen and hydrogen react to form NH 3


• carbon and hydrogen bond to form a molecule of CH 4
  For each reaction, give:
  a. the number of electrons in the outermost energy level
  b. the Lewis structure of the product that is formed
  c. the name of the product

4. A chemical compound has the following Lewis notation:

X Y

ו ××

ו ××

H

a. How many valence electrons does element Y have?

b. What is the valency of element Y? (remember that the valency of an

atom is the number of chemical bonds it can form.)

c. What is the valency of element X?

d. How many covalent bonds are in the molecule?

e. Suggest a name for the elements X and Y.

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Chemistry: Matter and Materials 107