Matter Waves and Structure of the Atom

Matter Waves:

• Louis de Broglie’s hypothesis: Every moving particle has a wavelength associated with it.
• De Broglie wavelength:: $$λ = {h \over p}$$ where λ is the wavelength, h is Planck’s constant, and p is the momentum.
• Electron microscope: Utilizes the wave-particle duality of electrons to achieve higher resolution than opticalmicroscopes.

Structure of the Atom:

• Basic building blocks: Protons (positively charged), Neutrons (neutral), Electrons (negatively charged).
• Atomic number (Z): The number of protons in the nucleus of an atom identifies the element.
• Mass number (A): The sum of protons and neutrons in the nucleus.
• Isotopes: Atoms of the same element with different numbers of neutrons, leading to different mass numbers.
• Rutherford’s gold foil experiment: Demonstrated that most of an atom’s mass is concentrated in a small, dense nucleus surrounded by electrons.
• Bohr’s model of the atom: Electrons occupy specific energy levels, with transitions between levels releasing or absorbing photons of light.
• Quantum mechanics and atomic orbitals: Electrons are described by wave functions that define regions of high probability where they may be found.
• Electron configurations and the periodic table: The arrangement of electrons in atomic orbitals determines an element’s properties and position in the periodic table.
• Pauli exclusion principle: No two electrons in an atom can have the exact same set of quantum numbers.
• Hund’s rule: Electrons in the same orbital tend to have the same spin.

Electron Configurations

• Aufbau principle: Electrons fill atomic orbitals in order of increasing energy.
• Electron configurations: Notation representing the distribution of electrons in atomic orbitals.
• Valence electrons: Electrons in the outermost energy level, mainly responsible for chemical reactions.
• Inert gases: Elements with stable electron configurations, making them highly unreactive.

Quantum Numbers

• Principal quantum number (n): Describes the energy level of an electron (1,2,3…).
• Azimuthal quantum number (l): Describes the subshell within an energy level (s, p, d, f).
• Magnetic quantum number (ml): Represents the orientation of an electron orbital in space.
• Spin quantum number (ms): Represents the two possible spin states of an electron (up or down).