Chapter 4.4: Oxidation-Reduction (Redox) Reactions

Flashcards from Chapter 4.4 of Chemistry: The Molecular Nature of Matter and Change.

Redox reaction

A reaction involving the oxidation and reduction of two substances at the same time

• Contributes to both ionic and covalent compounds as electrons are transferred or shifted

• Seen with 2Na⁺ + Cl₂^- → 2NaCl, as Na loses a negative charge (oxidized) and Cl gains a negative charge (reduced)

Electron transfer

What occurs between atoms in an ionic compound

Electron shift

What occurs between atoms in a covalent compound, with no ions formed yet still a difference in charge

Oxidation

The loss of electrons to an oxidizing agent

• In 2Na⁺ + Cl₂^- → 2NaCl, Na has this done to it as it loses negative electrons to Cl

Reduction

The gain of negatively-charged electrons to a reducing agent

• Term refers to the total positive charge going down

• In 2Na⁺ + Cl₂^- → 2NaCl, Cl has this done to it as it gains negative electrons from Na

Oxidizing agent

What receives the negatively-charged electrons from an oxidized atom, thus becoming reduced with more negative charges

• Term refers to the other substance’s change after losing electrons

• In 2Na⁺ + Cl₂^- → 2NaCl, Cl is this as it removes electrons from Na

  • Makes something more positive by becoming more negative

Reducing agent

What loses electrons to a reduced atom, thus becoming oxidized with fewer negative charges

• Term refers to the other substance’s change as it gains negatively-charged electrons

• In 2Na⁺ + Cl₂^- → 2NaCl, Na is this as it contributes electrons to Cl

  • Makes something more negative by becoming more positive

Oxidation number (ON)

A number stating the charge an individual atom would have, if all its shared electrons were transferred to the atom that attracts them more strongly

• Sum of multiplied charges must equal 0 or stated charge

• Written as (+2) and not (2+)

Ion charge

What is the oxidation number for each element in a binary ionic compound?

0 or the stated charge

What must the sum of all multiplied oxidation numbers be in an equation?

Oxidation rules

The oxidation number for each element in a covalent compound is determined by these

0

What is the oxidation number for an atom in its elemental form, like Na or C?

-1

What is always the oxidation number for F?

-1

What is the oxidation number for O, when in a peroxide?

-2

What is the oxidation number for O outside of a peroxide or compounds with F?

+1

What is the oxidation number for H when bound to a nonmetal?

-1

What is the oxidation number for H when bound to a metal or B?

-1

What is the oxidation number for elements in group 17, when bound to metals, non-O nonmetals, and non-F halogens?