Cosmic Expansion and The Big Bang Theory

• Chemistry is a branch of science that studies matter.
• Cosmology studies the origin and the fate of the universe.
• The Big Bang Theory states the universe formed from an indefinite dense, hot core of material.
• Postulates are the universe is constantly expanding starting from a packed state of hot and enormous matter.
• The Big Bang event occurred 13.7 billion years ago from a singularity.
• Inflation is a mysterious particle or force that accelerates the universe's expansion.
• The Dark Ages were a period when clouds of dark hydrogen gas cooled and coalesced.
• First stars began to form when gas clouds collapsed, initiating stellar fusion.
• Galaxy formation occurs as gravity causes galaxies to form, merge, and drift.
• Matter is composed of varying combinations of the 114 elements.
• Atoms are the building blocks of matter.
• The existence of all matter is believed to have started with the birth of the universe.

Cosmic Expansion

• Edwin P. Hubble made a discovery at Mount Wilson Observatory in California using the 100-inch Hooker Telescope in the early 1930s.
• Cepheid variables are a class of pulsating stars.

Big Bang Theory

• Big Bang Theory explains that the universe began in a hot, dense state and is constantly expanding
• Evidence includes Hubble Expansion/Redshift, Cosmic Microwave Background (CMB), and Big Bang Nucleosynthesis (BBN).
• Einstein's Model (1917) proposed a static, finite, and homogeneous universe.
• Lemaître's Model opposed Einstein's model, saying it was not physically realistic.

Evidence for Big Bang

• Edwin Hubble (1930s) used the Hooker Telescope to observe variable stars in galaxies beyond the Milky Way.
• Hubble discovered galaxies are moving away, proving the universe is expanding.
• Redshift: as galaxies move away, light shifts toward the red spectrum.

Cosmic Microwave Background (CMB)

• Gamow, Alpher, and Herman predicted CMB in the 1940s.
• Penzias & Wilson discovered CMB in 1964, confirming afterglow radiation from the Big Bang.
• CMB indicates the transition from ionized to neutral gas about 400,000 years after the Big Bang.

Big Bang Nucleosynthesis (BBN)

• Gamow, Herman, and Alpher proposed BBN.
• Formation of light elements (He-4, He-3, Li-7, Deuterium) occurred in the first few minutes after the Big Bang.
• BBN confirms the early universe was extremely hot and dense.

Chemical vs. Nuclear Reactions

• A Chemical Reaction changes substance identity.
• A Nuclear Reaction involves fusion (combining nuclei) or fission (splitting nuclei).

Introduction to Nuclear Reactions

• Alpha particle: (High-energy) helium nuclei consisting of two protons and two neutrons.
• Beta particle: (High-energy) electrons.
• Positron: Particles with the same mass as an electron but with 1 unit of positive charge.
• Proton: Nuclei of hydrogen atoms.
• Neutron: Particles with a mass approximately equal to that of a proton but with no charge.
• Gamma ray: Very high-energy electromagnetic radiation.
• James Chadwick discovered the neutron in 1932, it's a previously unknown neutral particle produced along with 12C by the nuclear reaction between 9Be and 4He.

Formation of Elements

• Light elements include hydrogen, helium, and lithium.
• Primordial or BBN refers to the process of producing the light elements after the Big Bang.
• Nuclear Fusion occurs when hydrogen atoms gain protons and neutrons to form helium or lithium.
• Protons and neutrons are held together by the strong force, overcoming repulsion between protons.
• Formation of Heavier Elements is when fusion in stars combines protons and neutrons to create heavier nuclei.
• Big Bang & Star Formation: Atoms formed in the Big Bang merged into gas clouds, contracting under gravity and leading to star formation.
• Stellar Nucleosynthesis is when heavy elements are formed in stars and scattered by explosions, involving:
  • Nuclear Fusion (forms nuclei up to iron, releasing energy).
  • Neutron Capture & Beta Decay (forms nuclei heavier than iron, requiring energy).
• Energy in Stars: Stars need energy from fusion reactions between light elements to exist.
• Big Bang Contribution: Mostly produced hydrogen and helium, which serve as the foundation for heavier element formation in stars.
• Energetic Collisions: Atomic collisions alter structures, releasing large amounts of energy, making stars hot and bright.
• Star Power Source: Stars are fueled by nuclear fusion, primarily converting hydrogen into helium.

Stellar Evolution

• Elements heavier than beryllium are formed through stellar nucleosynthesis.
• Stellar nucleosynthesis - elements are formed within the stars.
• Stellar evolution - changes of a star during its lifetime, from the protostar phase to its stellar death: supernova.
• Nuclear fusion - how elements hydrogen, helium, and small amounts of lithium and beryllium were formed.

Nucleosynthethic Pathways:

• Triple Alpha Process is a set of nuclear fusion reactions where three helium-4 atoms are transformed into Carbon.

• CNO cycle is a catalytic cycle where stars convert hydrogen into helium in a larger or hotter main sequence star.

• Alpha Ladder converts helium into heavier elements.

• S- process refers to the slow addition of neutrons over hundreds or thousands of years.

• S-process may produce stable isotopes up to lead (Pb).

• R-process happens only during stellar explosions.

• Supernova is the explosion of a star, and the largest explosion that takes place in space.

• Stars burn fuel to produce energy and shine, they then must evolve and live through a life cycle.

• The Universe consists of approximately 92% hydrogen and 8% helium atoms by number (or 75% hydrogen and 25% helium by mass).

• All other elements were formed by nuclear interactions undergoing in stars.

• Nebulae are interstellar gas/dust clouds within the interstellar medium.

• The rotation speed of each cloud gradually increases due to conservation of angular momentum.

• The rotating ball collapses into a thin disk with most of the mass concentrated near the center eventually forming a protostar.

Chemistry Before Modern History

• Mesopotamians: Utilized metals like gold and copper and other materials such as dyes, glass, paints, and perfumes.
• Egyptians: Perfected the use of bronze, dye, and glass.
• Chinese: Had their own processes for metalwork and ceramic materials and focused on finding minerals and plants that can prolong life.
• Indians: Were well-known for manufacturing dyes, glass, cement, solutions for textiles, and soap.
• Arabs and Muslims: Contributed to the literature of chemistry.
• Alchemists aimed to transmute base metals to gold.
• Photoscience is the beginning of real science.
• Pseudoscience includes beliefs that are not real science.
• Atom is the smallest unit of matter and was theorized by some ancient Greeks.
• Democritus and Leucippus came up with the idea of the atom.
• Atomos is a Greek term for "undivided."
• Atomism states that atoms make up everything in the universe, Atoms are colliding in the void, and cannot be divided, Atoms are solid homogeneous.

Non-Atomistic Views of Greeks

• Anaxagoras believed in an infinite number of elementary particles.
• Empedocles believed in 5 elements: fire, water, earth, air.
• Plato believed in geometrical solids.
• Aristotle believed that atoms cannot be seen, so it is untrue.
  • Aristotle's 4 elements were the same as Empedocles'.
  • Aristotle's 4 properties were dry, cold, hot, wet.
• Robert Brown discovered Brownian Motion, he described it as a billiard ball.
• JJ Thomson discovered electrons through the Cathode Ray Tube (CRT) experiment.
  • Thomson found out that atoms are composed of electrons.
  • Thomson presented the plum pudding model of the atom.
• Ernest Rutherford was a student of Thomson.
• Rutherford found that an atom is composed of a nucleus.
  • Rutherford discovered the alpha particle.
  • Rutherford conducted the gold foil experiment.
  • Rutherford's model of the atom is like a miniature solar system.
• Niels Bohr discovered energy levels.
  • Bohrs atomic model is the "Bohr model"
• Schrodinger and Heisenberg discovered orbitals in the atom.
• James Chadwick's discovery isnt provided.