Physical Science - Light Elements and Isotopes

Physical Science - Light Elements

• Big Bang Nucleosynthesis: Process creating light elements
• Hydrogen and Helium: First light elements formed
• Rapid cooling: From 10³² to 10⁹
• Quarks and Gluons: Condensed into nucleons, forming light elements
• Stellar Nucleosynthesis: Formation of heavy elements by fusion in stars
• Nebulas: Clouds of Hydrogen and Helium
• Protostar: Mass of Hydrogen and Helium
• Star element production: Stars produce elements up to Iron.
• Supernova nucleosynthesis: Explosive star death creating heavier elements
• Extreme temperatures and abundant neutrons: Key characteristics of Supernova explosions.
• Neutron capture: Neutrons are captured by nuclei, forming heavier elements.

Chemical Elements and Isotopes

• Isotopes: Forms of an element with the same atomic number but different atomic mass, or mass number.
• Stable Isotopes: Not radioactive
• Unstable Isotopes: Radioactive, decay emitting positrons and neutrinos to form new elements.
• Positrons: Same mass as electrons but positive charge
• Neutrinos: Massless and chargeless

Atomic Theory: From Ancient Greeks to Present

• Empedocles' Theory: Matter made of four fundamental substances.
• Democritus' Theory: All matter composed of indivisible atoms ('atomos')
• Aristotle's Theory: Expanded Empedocles' theory, adding his own ideas about the transformation of elements.

The Structure of the Atom

• John Dalton's Atomic Theory: Matter composed of atoms, all atoms of a given element are identical, compounds are formed by combining atoms, chemical reactions involve rearranging atoms.
• Four Main Concepts of Dalton's Atomic Theory: Listed
• Scientific Laws About Chemical Reactions: Law of Conservation of Mass and Law of Definite Proportions
• Joseph Louis Proust and Law of Definite Proportions: Detailed
• Joseph John Thomson (J.J. Thomson): Plum pudding model, discovered electrons
• Ernest Rutherford: Model atom with a positive nucleus containing most of its mass, discovered protons in his experiment
• Niels Bohr: Planetary model of the hydrogen atom
• James Chadwick: Discovered neutrons in the atomic nucleus
• Quantum Mechanical Model: Quantum, energy levels, orbitals
• Each sublevel contains a set of orbitals
• No orbital can contain more than two electrons
• Synthetic or Artificial elements: Atomic numbers 99-118, radioactive
• Radioactivity: Unstable nucleus breakdown

Bonding and Physical Properties of Matter

• Ionic Bond: Metal reacting with a nonmetal, electron transfer, cation (positive) and anion (negative) formation.
• Covalent Bonds: Sharing of electrons, nonmetal to nonmetal chemical bond, one, two, or three pairs of electrons may be shared
• Two types of Covalent Bond- non-polar and polar
• Metallic Bonds: Metallic cations attracted to delocalized electrons
• Covalent compounds: Low melting point, lack electrical conductivity when solid
• Ionic compounds: High melting point, solid form at room temperature, good electron conductors

Electronegativity and Polarity

• Electronegativity: Atom's tendency to attract electrons
• Electronegativity Trend: Increasing from left to right, decreasing from top to bottom
• Polarity: Uneven partial charge in a compound, resulting from differing electronegativities in atoms
• Polar Molecules (Dipoles): Electrons attracted to one atom in a molecule more than the other. Slightly positive and negative ends
• Nonpolar Molecules: Equal electronegativity values and electron sharing
• Intermolecular Forces: Determining factor of substance state, solid, liquid, or gas at room temperature.

Intermolecular Forces and Interactions

• Types of intermolecular forces: Ion-dipole, dipole-dipole, dispersion (London) forces
• Hydrogen Bonding: Special type of dipole-dipole interaction (hydrogen with electronegative atom)

Stoichiometry

• Stoichiometry: Measurement based on laws of chemical combination.
• Formula Mass/Molecular Mass: Based on ionic/covalent bonds.
• Mole: Counting unit of atoms/molecules (6.02 x 10²³)
• Percentage Composition: Finding percentage of each element in a compound.
• Calculating Formulas: Determining elements and proportions of weights in experimental data.
• Empirical Formulas: Simplest ratio of atoms in a compound.
• Mole-to-Mole Conversion: Calculating moles of one substance from moles of another, using balanced equations.
• Moles-to-Grams Conversion: Converting between moles and grams of a compound
• Mass-to-Mass Conversion: Calculation between masses of substances, using molar masses and balanced reactions.

Rates of Chemical Reactions

• Collision Theory: Relationship between collisions and reaction rates
• Factors affecting rates: Concentration, particle size, temperature, catalysts
• Catalysts: speed up reactions

Limiting Reactant and Yield

• Limiting Reactant/Reagent: Reactant in short supply, limits product formation
• Excess Reactant/Reagent: Other reactant present in more than needed amount
• Theoretical Yield: Expected product amount based on calculations
• Actual Yield: Product amount produced in the experiment
• Percent Yield: Comparing actual and theoretical yield