Chemistry Chapter 8: Unit 2

Colored Neon Lights: Explanation of why different neon lights have various colors, depending on the gas used and its electron configurations.
Electron Configuration: Definition and importance in understanding atomic structure.
Rules for Writing Electron Configuration:
- Pauli’s Exclusion Principle: No more than two electrons can occupy the same orbital, and they must have opposite spins.
Example of Electron Configuration:
- Magnesium (Mg): Electron configuration is given as a case study.
Valence Electrons and Valence Shell:
- Definition: Valence electrons are the electrons in the highest principal energy shell, while core electrons are those in lower energy shells.
Blocks of the Periodic Table:
- S-block: Example element: Lithium (Li)
- P-block: Example element: Nitrogen (N)
- D-block: Example element: Iron (Fe)
- F-block: Example element: Uranium (U)
Periodic Trends: Discussion on how certain parameters change across and down the periodic table:
- Atomic Size: Trend on how atomic size increases or decreases.
- Ionization Energy: How ionization energy varies across periods and groups.
- Metallic Character: Trends regarding how metallic character increases or decreases.

Barcodes of Elements: Unique patterns of absorption and emission spectra for individual elements.
- Continuous Spectrum: Formed when light passes through a prism, showing a range of colors without distinct lines.
- Emission Spectrum: Characterized by specific wavelengths emitted by an excited gas (Example: Mercury) showing a distinct pattern.

The Bohr Model:
- Concept of Quantum Levels: Electrons can only occupy fixed energy levels (shells).
- Excitation of Electrons: Electrons absorb a specific amount of energy to move to higher energy levels.
- Relaxation of Electrons: When electrons return to a lower energy state, they emit energy in the form of light waves at specific wavelengths.
Proof of Fixed Energy Levels: Demonstrates that electrons exist in discrete orbits around the nucleus.

Energy Levels and Transitions:
- Representation of different energy levels: $n = 1, 2, 3, 4, 5$.
- Excitation: Absorption process.
- Relaxation: Emission process.

Orbital Filling Sequence:
- Order of Orbital Energy: The sequence of orbital filling is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d.
Types of Orbitals:
- s-orbital: 1 orbital (spherical)
- p-orbital: 3 orbitals (dumbbell-shaped)
- d-orbital: 5 orbitals (clover-shaped)
- f-orbital: 7 orbitals (complex shapes)

Representation of Orbitals:
- Orbitals are often depicted as squares; electrons are represented as arrows within these squares.
- Electron Spin: The direction of the arrow indicates the spin of the electron.
Pauli’s Exclusion Principle: Emphasizes that no orbital can hold more than two electrons with opposite spins.

The electron configuration is a listing that represents how electrons are distributed among the various orbital subshells.
Example Configurations:
- Krypton (Kr) with 36 electrons: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6$ .
- Rubidium (Rb) with 37 electrons: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^1$ or as shorthand $[Kr]5s^1$ .

Determine Atomic Number: Atomic number of Mg is 12, indicating 12 protons and 12 electrons.
Ground State Orbital Diagram: Illustrating the distributions of electrons in energy levels ($1s$, $2s$, $2p$, $3s$, $3p$).
Filling Order:
- Electrons are added one at a time to each box until all electrons are placed, following the pairing rule for spins.
Final Configuration: The configuration for Mg derived from the diagram: $1s^2 2s^2 2p^6 3s^2$ or $[Ne]3s^2$ .

Examples of electron configurations need to be derived for various elements:
- Sodium (Na), Neon (Ne), Vanadium (V).

Definition of Valence Electrons: The electrons present in the outermost shell, important for chemical behavior.
Core Electrons: Electrons in the energy levels beneath the valence shell.
Further examples:
- Rubidium (Rb): Highest principal energy shell is 5 with 1 valence electron, 36 core electrons.
- Krypton (Kr): Highest principal energy shell is 4 with 8 valence electrons, 28 core electrons.

Blocks of Periodic Table: Visual representation of the arrangement of s, p, d, and f blocks and corresponding subshells.

Detailed arrangement of electron configurations for the first elements categorized by their blocks.

Trends Summary:
- Atomic size increases down a group due to additional electron shells.
- Atomic size decreases across a period due to increasing nuclear charge attracting electrons closer.

Ionization Energy Increases:
- Generally increases across a period and decreases down a group. Smaller atoms require more energy to remove an electron.
Example Values:
- Hydrogen (H): 1312 kJ/mol.
- Helium (He): 2372 kJ/mol.
Comparison Analysis: Various elements show varying ionization energies based on size and nuclear charge.

General Trends:
- Atomic Size: Increases down a column, decreases across a row.
- Metallic Character: Increases down a column, decreases across a row.
- Ionization Energy: Decreases down a column, increases across a row.

Which atom of each pair is larger?
- a. Si or S
- b. H or He
Which atom in each pair is more metallic?
- a. Si or S
- b. H or He
Which atom has the higher ionization energy? Smaller size.
- a. Na or S
- b. Ge or Br.