Valence Electrons and Lewis Structures

Dr. B explains how to calculate the total number of valence electrons for molecules and ions, using examples like CH4, O2, SO4 2-, and NH4+. The video covers the importance of understanding valence electrons as a first step in drawing Lewis structures.

What is the total number of valence electrons in a CH4 molecule?

• 12

• 10

• 8

• 6

Which group in the periodic table does carbon belong to?

• Group 4

• Group 1

• Group 6

• Group 2

How many valence electrons does oxygen contribute in an O2 molecule?

• 20

• 12

• 6

• 14

What is the total number of valence electrons in an O2 molecule?

• 16

• 20

• 22

• 18

In the sulfate ion (SO4 2-), how many extra electrons are added due to the charge?

• 4

• 3

• 2

• 1

What is the total number of valence electrons in the sulfate ion (SO4 2-)?

• 30

• 34

• 28

• 32

How does a positive charge affect the number of valence electrons in an ion?

• It has no effect

• It doubles the electrons

• It removes an electron

• It adds an electron

What is the total number of valence electrons in the NH4+ ion?

• 8

• 7

• 6

• 9

Why is it important to find the total number of valence electrons in a molecule?

• To calculate the boiling point

• To draw Lewis structures

• To predict the color of the molecule

• To determine the molecular weight

What is the first step in drawing Lewis structures for molecules?

• Identifying the type of bond

• Determining the total number of valence electrons

• Finding the molecular formula

• Calculating the molecular mass