LEC 33 (8.1-8.2)

Quick Recap: Ionization Energy and Electron Affinity

  • Ionization Energy:

    • The amount of energy required to remove one electron from the nucleus of an atom.

  • Electron Affinity:

    • The energy released when an electron is added to an atom.

  • Trends:

    • Ionization energy increases from left to right across a period and from bottom to top within a group.

Practice Problem

  • Question: Which of the following elements has the highest first ionization energy? (Options: Mg, Na, Ga, S)

  • Answer: S (sulfur) has the highest 1st ionization energy due to its position in the periodic table.

Introduction to Chemical Bonds

  • Types of Chemical Bonds:

    • Atoms form both transient and non-transient bonds as they interact. The primary types of bonds include:

    • Metallic Bonds:

      • Atoms held together by a "sea of electrons" around their nuclei.

    • Ionic Bonds:

      • Formed between ions through electrostatic attractions.

    • Covalent Bonds:

      • Involves sharing of electrons in localized bonds.

Lewis Structures

  • Rules for Drawing Lewis Structures:

    • Each Lewis structure has four sides, with a maximum of two electrons per side, totaling eight electrons.

    • Electrons should be kept apart whenever possible.

Chemical Nirvana and the Octet Rule

  • Octet Rule:

    • Atoms in period 2 or 3 gain or lose electrons to achieve a stable octet (eight valence electrons).

  • This rule can be extended to other periods on the periodic table.

Ionic Compounds and Bonding

  • Ionic Compounds:

    • Result from interactions between positive cations and negative anions due to charge differences.

    • Example: The formation of NaCl through the transfer of electrons from Na to Cl.

Lattice Energy in Ionic Compounds

  • Formation of ionic lattices is highly exothermic due to the strong attraction between ions.

  • Factors Influencing Lattice Energy:

    • Increases with:

    • Higher charges of ions.

    • Shorter ionic radii.

Practice Problems on Lattice Energy

  • Problem 1: Which of the following has the highest lattice energy? (Options: NaF, CsI, CaO)

    • Answer: CaO has the highest lattice energy due to higher ionic charges (+2 and -2).

  • Problem 2: Which of the following has the highest lattice energy? (Options: NaCl, LiCl, KCl)

    • Answer: LiCl has the highest lattice energy due to a smaller radius compared to NaCl and KCl.

Transition Metals and the Octet Rule

  • Transition metals (d-block) may have more than eight electrons in their valence shells due to their unique electron configurations.

Key Takeaways

  • Quaternary structures allow for complex functions surpassing those of tertiary structures.

  • The cooperative binding of hemoglobin contrasts with the non-cooperative binding of myoglobin.

Homework for Next Class

  • Be proficient in using Lewis structures and predicting lattice energy. Prepare for further discussions on bonding and electronegativity next class!