Valence Electrons and Oxidation Numbers

The video tutorial introduces valence electrons, explaining their role in the outermost orbitals of atoms and their distribution across the periodic table. It then demonstrates how to draw Lewis diagrams for elements like Krypton, Fluorine, and Oxygen, focusing on the placement of valence electrons. The tutorial concludes with an explanation of oxidation numbers, using lithium as an example, and describes the crisscross method for determining chemical compound formation.

What are valence electrons?

• Electrons in the outermost shell

• Electrons in the innermost shell

• Neutrons in the nucleus

• Protons in the nucleus

How many valence electrons are there in the third energy level?

• Eight

• Six

• Four

• Two

In the first three periods of the periodic table, how does the number of valence electrons change as you move from left to right?

• Decreases from eight to one

• Remains constant

• Fluctuates randomly

• Increases from one to eight

What is the first step in drawing a Lewis diagram for Krypton?

• Draw a cross

• Draw a circle

• Draw eight dots around the symbol

• Draw the symbol 'Kr'

How many valence electrons does Fluorine have?

• Seven

• Six

• Eight

• Five

What is the oxidation number of an atom that loses one electron?

• Positive two

• Positive one

• Zero

• Negative one

Why is it easier for Lithium to lose one electron rather than gain seven?

• It is a metal

• It has only one valence electron

• It has a full outer shell

• It is a noble gas

What is the oxidation number of sulfur in calcium sulfide?

• Negative two

• Positive two

• Zero

• Positive one

How many calcium atoms are needed to balance the charge with one sulfur atom in calcium sulfide?

• Two

• Three

• One

• Four

What method is used to determine the number of atoms in a compound using oxidation numbers?

• Crisscross method

• Cross method

• Dot method

• Line method