Oxidation and reduction | Redox reactions and electrochemistry | Chemistry | Khan Academy

TL;DR

Sodium chloride is formed through an ionic bond between sodium and chlorine atoms, while water molecules have covalent bonds with an unequal sharing of electrons.

Transcript

Let's think a little bit about the molecule sodium chloride. If we look at the periodic table right over here, we see that sodium is a Group 1 element. It's an alkali metal. It has one valence electron. It's also not too electronegative. It's sitting here on the left-hand side of the periodic table. We know the general trend for electronegativity i... Read More

Key Insights

• 💁 Sodium chloride forms through an ionic bond between sodium and chlorine, where sodium donates an electron to chlorine.
• 💦 Water molecules have covalent bonds with unequal electron sharing due to the higher electronegativity of oxygen.
• 🫀 Oxidation states are a hypothetical representation of ionic charges that help analyze reactions, even in cases where atoms are involved without oxygen.

Questions & Answers

Q: How does sodium chloride form an ionic bond?

Sodium chloride forms an ionic bond because sodium has one valence electron, which it is likely to give away, and chlorine has a high electronegativity and tends to gain electrons. This results in the formation of sodium cations and chloride anions that are attracted to each other.

Q: What are the characteristics of water molecules?

Water molecules consist of one oxygen atom bonded to two hydrogen atoms through covalent bonds. The electrons in these bonds are shared, but the unequal electronegativity between oxygen and hydrogen leads to partial negative charges on the oxygen end and partial positive charges on the hydrogen ends of the molecule.

Q: What is the purpose of oxidation states?

Oxidation states are an intellectual tool in chemistry used to analyze reactions. They assume hypothetical ionic charges for atoms in covalent bonds and provide a way to understand reactions by considering how oxidation (loss of electrons) and reduction (gain of electrons) occur.

Q: Does oxidation always involve oxygen?

No, oxidation does not always involve oxygen. While the term might suggest an association with oxygen, oxidation refers to the loss of electrons, and reduction refers to the gain of electrons. Oxygen is just one element that tends to be electronegative and "oxidize" other atoms by taking away their electrons.

Summary & Key Takeaways

• Sodium, a Group 1 element, is highly electropositive and is likely to give away its valence electron to form a positive sodium ion (cation).

• Chlorine, a Group 7 element, is highly electronegative and would gain an electron from sodium to become a negative chloride ion (anion).

• The ionic bond between sodium and chloride ions forms sodium chloride. In water molecules, covalent bonds between hydrogen and oxygen atoms have unequal electron sharing.