Atomic Structure Fundamentals

Atomic Structure

Subatomic Particles

• Protons:
  • Positive charge
  • Found in the nucleus
  • Number of protons determines the element
• Neutrons:
  • No charge
  • Found in the nucleus
  • Number of neutrons determines the isotope
• Electrons:
  • Negative charge
  • Found in energy levels (shells) around the nucleus
  • Number of electrons equals the number of protons (neutral atom)

Atomic Models

• Rutherford's Model:
  • Nucleus (protons and neutrons) surrounded by electrons
  • Electrons orbit the nucleus in energy levels
• Bohr's Model:
  • Energy levels are specific distances from the nucleus
  • Electrons jump to higher or lower energy levels by emitting or absorbing energy
• Quantum Mechanical Model:
  • Electron behavior is described by probability distributions (orbitals)
  • Electrons exist in a cloud of probability around the nucleus

Electron Configuration

• Valence Electrons:
  • Outermost energy level electrons
  • Determine the chemical properties of an element
• Electron Shells:
  • Energy levels around the nucleus
  • Can hold a specific number of electrons
• Aufbau Principle:
  • Electrons occupy the lowest available energy level
  • Electrons fill orbitals in a specific order (s, p, d, f)

Atomic Radius and Ionization Energy

• Atomic Radius:
  • Distance from the nucleus to the outermost electron
  • Decreases from left to right across a period
• Ionization Energy:
  • Energy required to remove an electron from an atom
  • Increases from left to right across a period

Atomic Structure

Subatomic Particles

• Protons have a positive charge, are found in the nucleus, and determine the element based on their number.
• Neutrons have no charge, are found in the nucleus, and determine the isotope based on their number.
• Electrons have a negative charge, are found in energy levels (shells) around the nucleus, and equal the number of protons in a neutral atom.

Atomic Models

Rutherford's Model

• The nucleus (protons and neutrons) is surrounded by electrons.
• Electrons orbit the nucleus in energy levels.

Bohr's Model

• Energy levels are specific distances from the nucleus.
• Electrons jump to higher or lower energy levels by emitting or absorbing energy.

Quantum Mechanical Model

• Electron behavior is described by probability distributions (orbitals).
• Electrons exist in a cloud of probability around the nucleus.

Electron Configuration

• Valence electrons are located in the outermost energy level and determine the chemical properties of an element.
• Electron shells are energy levels around the nucleus that can hold a specific number of electrons.
• The Aufbau principle states that electrons occupy the lowest available energy level and fill orbitals in a specific order (s, p, d, f).

Atomic Radius and Ionization Energy

• Atomic radius is the distance from the nucleus to the outermost electron, and it decreases from left to right across a period.
• Ionization energy is the energy required to remove an electron from an atom, and it increases from left to right across a period.

Stoichiometry

• Study of quantitative relationships between reactants and products in chemical reactions

Key Concepts

• Mole (mol): unit of measurement representing 6.022 x 10^23 particles (atoms, molecules, ions, or electrons)
• Molar mass (M): mass of one mole of a substance, usually expressed in grams per mole (g/mol)
• Avogadro's number (NA): 6.022 x 10^23, used to convert between moles and particles

Stoichiometric Calculations

• Mole-to-mole conversions: use mole ratio from balanced equation to convert between moles of reactants and products
• Mole-to-mass conversions: use molar mass to convert between moles and mass (grams)
• Mass-to-mass conversions: use mole ratio and molar masses to convert between masses of reactants and products

Limiting Reactant

• Definition: reactant that is completely consumed in a reaction, limiting the amount of product formed
• Identification: identify limiting reactant by comparing mole ratios of reactants and their respective masses

Percent Yield

• Definition: ratio of actual yield of a product to the theoretical yield, expressed as a percentage
• Calculation: (actual yield / theoretical yield) x 100%

Empirical Formula

• Definition: simplest whole-number ratio of atoms in a compound
• Calculation: use mole ratios of elements to determine empirical formula

Molecular Formula

• Definition: actual formula of a compound, showing number of atoms of each element
• Calculation: use empirical formula and molecular mass to determine molecular formula