Recording-2025-02-19T15_04_41

Electrons reside in specific energy levels or shells, denoted by the principal quantum number (n).
Example: Sodium (Na) has an electron configuration ending in 3s1; thus, its outermost electron is in the n=3 shell.
First Ionization Energy: The energy required to remove the outermost electron from the n=3 shell.
- For sodium: 496 kJ/mol is needed to ionize the outer electron.

Group Trend: As you move down a group in the periodic table:
- Atoms increase in size due to additional shells (
- The outermost electron is further from the nucleus, experiences increased shielding, thus requires less energy to remove.
Period Trend: As you move across a period in the periodic table:
- Atoms gain protons, increasing the positive charge of the nucleus.
- Electrons are more tightly held due to increased nuclear attraction, resulting in higher ionization energies.

Complete shells result in lower energy and greater stability.
Removing an electron from a closed shell (e.g., noble gases) requires significantly more energy due to the stability of closed shells.
Example: Lithium has a first ionization energy of 520 kJ/mol. The second ionization energy is substantially higher (7230 kJ/mol) due to stronger attraction of the remaining electrons to the nucleus.

Electron affinity is the amount of energy released when an electron is added to an atom.
Example: Fluorine has a high electron affinity, releasing -328 kJ/mol.
- As you go down a group, electron affinity decreases because the outermost electron is less tightly held due to increased shielding and distance from the nucleus.
Lithium shows a lower electron affinity (-59.6 kJ/mol) because adding an electron into a less stable configuration provides a smaller energy release.

Ionization occurs through various methods, such as:
- Photoelectric Effect: Electrons are ejected from a surface when it absorbs energy from light (photon).
- Photoelectron Spectroscopy: Measures the energy required to remove electrons. Peaks in spectra indicate the energy levels of the electrons being removed (outer to inner shells).

Discussion of calculating energy required to remove electrons in spectroscopy contexts.
Relevant Equation: Speed of light relation (c = λ ×ν) assists in finding the energy of emitted photons/electrons.
Demonstrated need for unit conversions (e.g. nanometers to meters or picometers).
Example calculation outlined for removing an n=2 electron (97 nm wavelength). The shorter the wavelength, the greater the energy involved in the interaction.