Oxidos Parte 1

Summary

The video introduces the formulation and naming of oxides, reviewing oxidation numbers and demonstrating how to write and balance oxide-forming reactions.

Key concepts

• An oxidation number represents the charge an atom would have if bonding electrons were assigned to one atom, as in an ionic bond.
  • Losing electrons corresponds to a positive oxidation number.
  • Gaining electrons corresponds to a negative oxidation number.
  • Elements can have more than one oxidation number. For example, iron can be +2 or +3, while oxygen is usually −2 in oxides.
• Oxides are compounds made of oxygen and another element:
  • Oxygen combined with a metal forms a basic oxide.
  • Oxygen combined with a nonmetal forms an acidic oxide.
• In an oxide formula, the less electronegative element is written first, followed by oxygen.

Formulating and balancing oxide reactions

The examples illustrate this process:

1. Write the elements in the correct order: metal first, oxygen second.
2. Use the elements’ oxidation numbers to determine the subscripts. Cross the magnitudes of the oxidation numbers, then simplify the subscripts when possible.
3. Check that the compound is electrically neutral overall.
4. Balance the reaction by placing coefficients in front of formulas so that the number of each type of atom is equal on both sides. Coefficients must not be confused with subscripts, which are part of a compound’s formula.
5. Remember that elemental oxygen in the reactants is written as O₂.

Examples:

• Sodium oxide: Na₂O Balanced reaction: 4Na + O₂ → 2Na₂O

• Iron can form two oxides:

  • FeO, with iron at +2: 2Fe + O₂ → 2FeO
  • Fe₂O₃, with iron at +3: 4Fe + 3O₂ → 2Fe₂O₃

These formulas and balanced equations clarify several garbled phrases in the auto-generated subtitles.

Three naming systems

The video presents three ways to name oxides:

• Traditional nomenclature: Uses different endings for a metal’s lower and higher oxidation states. For iron, FeO is ferrous oxide and Fe₂O₃ is ferric oxide. If a metal has only one common oxidation state, this distinction is not needed.
• Prefix (systematic) nomenclature: Uses prefixes to indicate how many atoms of each element are present. Common prefixes are mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and deca-. For example, FeO is iron monoxide, while Fe₂O₃ is diiron trioxide.
• Stock nomenclature: Names the oxide and gives the metal’s oxidation state in Roman numerals: iron(II) oxide for FeO and iron(III) oxide for Fe₂O₃.

Speakers and sources

• One unnamed instructor or teacher presents the lesson.
• The periodic table is cited as a reference for oxidation numbers.