Matter, Atoms, and Electron Configuration

• These notes cover the Particulate Nature of Matter, the Nuclear Atom, and Electron Configuration.

Particulate Nature of Matter

• This includes elements, compounds, mixtures, Kinetic Molecular Theory (KMT) and Kinetic energy, and temperature.

• Elements are pure substances that consist of only one type of atom.

• Oxygen (O₂) and Iron (Fe)

• Compounds contain two or more elements that are chemically bonded in fixed ratios.

• Water (H₂O) and Carbon Dioxide (CO₂)

• Mixtures consists of physical combinations of multiple substances that are not chemically bonded.

• Air and Saltwater

• Homogeneous mixtures contain uniform composition like a solution.

• Heterogeneous mixtures contain non-uniform composition

• Sand and Iron Filings

• Filtration, distillation, and chromatography are separation techniques.

• Chemical reactions are required to separate compounds, physical methods are used with mixtures.

Kinetic Molecular Theory (KMT)

• Particles are in constant, random motion.
• The volume of particles is negligible compared to the container volume.
• There are no intermolecular forces, this is an ideal gas assumption.
• Collisions are elastic, with no energy loss.
• Solids have a fixed shape and volume, where particles vibrate in place.
• Liquids have a fixed volume but variable shape where particles slide past each other.
• Gases have variable shape and volume, where particles move freely.
• Real gasses deviate at high pressure and low temperature.

Kinetic Energy and Temperature

• Temperature measures the average kinetic energy (KE) of particles.
• Average KE = (3/2) * kB * T.
• Heat is energy transfer whereas temperature is a measure of thermal energy.
• Thermal Expansion is when increased KE causes particles to vibrate/move more, leading to expansion.
• Temperature does not measure the total energy, a larger cold object can have more thermal energy than a small hot one.

Nuclear Atom

• This covers atomic models and mass spectra.

Atomic Model Evolution

• Dalton described atoms as indivisible spheres.
• Thomson proposed the "plum pudding" model with electrons in a positive cloud.
• Rutherford's gold foil experiment discovered a dense nucleus with mostly empty space.
• Bohr developed quantized electron orbits, known as the planetary model.
• The modern model describes the electron cloud (quantum mechanical model).
• Rutherford's alpha-scattering experiment showed the nucleus is small and positively charged.

Isotopes

• Isotopes are same element atoms with different numbers of neutrons.
• Carbon-12 vs. Carbon-14
• Isotopes have similar chemical behavior but different physical properties such as density and radioactivity.
• Notation: AXZ, where A = mass number and Z = atomic number.

Mass Spectra

• Mass spectra is used to determine isotopic abundance and calculation of average atomic mass.
• Process:
• Ionization turns atoms into ions.
• Acceleration sorts ions by mass-to-charge ratio (m/z).
• Detection shows peaks with abundance of each isotope.
• Average atomic mass = Σ (isotope mass × relative abundance).
• Chlorine (Chlorine-35: 75%, Chlorine-37: 25%): (35 × 0.75) + (37 × 0.25) = 35.5 u.

Electron Configuration

- This covers emission spectra and electron configuration rules.

Emission Spectra

• A continuous spectrum is white light dispersed into all wavelengths, creating a rainbow.
• A line spectrum has distinct colored lines.
• Hydrogen emission spectrum.
• The Balmer series has visible lines and transition to n=2.
• The Lyman series is UV light with transition to n=1, and the Paschen Series is IR with transition to n=3.
• Electrons emit photons when dropping energy levels.
• ΔE = hν

Electron Configuration

• Rules:
• Aufbau Principle: Fill lowest energy orbitals first.
• Pauli Exclusion: Max 2 electrons per orbital which have opposite spins.
• Hund’s Rule: Maximize parallel spins in degenerate orbitals.
• Notation:
• Orbital Order: Follow the n + ℓ rule (e.g., 4s fills before 3d).
• Carbon (Z=6): 1s² 2s² 2p².
• Chromium (Z=24): Exception → [Ar] 3d⁵ 4s¹.
• Orbital Diagrams use boxes and arrows to represent orbitals and spins.
• (e.g., 2p²: ↑↓ ↑ _)
• In ions, remove electrons from the outermost shell first
• Fe²⁺: [Ar] 3d⁶

Study Tips

• Practice Diagrams sketching atomic models, mass spectra, and orbital configurations.
• Flashcards should memorize isotope notation, KMT postulates, and electron rules.
• Complete past papers which focus on questions about separation techniques, mass spec calculations, and emission spectra.
• Mnemonic: “Sober People Don’t Forget” assists with orbital filling order (s, p, d, f).

Key Equations/Concepts to Memorize

• Average atomic mass = Σ (isotope mass × relative abundance).
• Hydrogen emission transitions (Balmer, Lyman, Paschen).
• Aufbau order up to n=4.

Common Mistakes

• Confusing mixtures and compounds.
• Forgetting Hund’s Rule in orbital diagrams.
• Misapplying isotope notation for example Carbon-14.

Study notes covering the particulate nature of matter, the nuclear atom, and electron configuration. Key concepts include elements, compounds, mixtures, and the Kinetic Molecular Theory (KMT). Learn about separation techniques such as filtration, distillation, and chromatography.