Chemistry Chapter 4 – Atomic Structure Video Clip: The Elements: Forged in Stars Video Clip: The Origin of the Elements

Original Thoughts The Greek thinker Aristotle classified the fundamental elements as fire, air, earth, and water. The ancient Chinese believed that the five basic components of the physical universe were earth, wood, metal, fire, and water. Pinyin, Wu Xing In India, 3rd century AD the five gross elements were claimed to be space, air, fire, water, and earth. Samkhya-karikas by Ishvarakrsna

Democritus Greek philosopher 400BC First to suggest the existence of atoms Atoms: smallest particle of an element that retains its identity Democritus could not support his ideas or answer the question what holds everything together so his concept was dismissed.

John Dalton English Chemist early 1800’s Dalton’s Atomic Theory All elements are composed of tiny indivisible particles called atoms Atoms of the same element are identical. The atoms of one element are different than atoms of other elements. Atoms of different elements can physically mix together or chemically combine in whole # ratios to form compounds. Chemical reactions occur when atoms are separated, joined, or rearranged.

Eugen Goldstein German physicist In1886 discovered positive particles by observing canal rays in a cathode ray tube filled with hydrogen gas

Thomson’s Atomic Model Plum Pudding JJ Thomson British physicist Found the electron in 1897 using cathode-ray tube experiments Negatively charged electrons in an atom were floating (or moving) in a sea of positive charge Plum Pudding Model established1904 Cathode Ray Tube

Ernest Rutherford New Zealand-born British chemist and physicist Found the nucleus 1911 Gold Foil Experiment He stated that the atom was a lot of empty space with a small, dense nucleus Rutherford’s Atomic Model

Moving past Rutherford Niels Bohr’s Model Danish Chemist Particle theory - 1911 e- travel in circular orbits called energy levels Each orbit has a quantized energy Looked at line spectra Important Vocabulary Energy Level: fixed energy of an e- Quantum: amount of energy required to move from one energy level to the next De Broglie Model French Chemist Wave theory - 1924 Similar to Bohr’s model, but e- act as waves not particles.

Erwin Schrödinger Werner Heisenberg Electron Cloud Atomic Model Erwin Schrödinger Austrian Physicist 1887-1961 Father of Quantum Mechanics Used mathematical equations to describe the location of the e-. Werner Heisenberg German theoretical Physicist 1901-1976 Awarded the 1932 Nobel Prize in Physics for the creation of quantum mechanics Can’t know position and momentum of an e- at the same time. e- don’t move in defined orbits

James Chadwick English physicist 1891-1974 In 1932 tracked particle emission from radioactive elements and discovered a particle with no charge: the neutron Explained why atomic mass and atomic # differed

The Changing Model of the Atom Democritus Dalton Thomson Plum Pudding Rutherford Nuclear Atom De Broglie – Wave Model Bohr Model Electron Cloud Model

The Atom Song

The subatomic particles summary Electrons have such a small mass compared to protons and neutrons we say electrons have no mass – but really they do. Subatomic Particle Location Charge Relative Mass (amu) Actual Mass (g) Electron (e-) e-cloud/ orbital Negative (1/1836) 9.11 x 10 -28 Proton (p+) nucleus Positive 1 1.67 x 10 -24 Neutron (n0) neutral (amu – atomic mass unit 1/12 of a Carbon-12 atom)

Isotopes Atoms of the same element can have different masses Isotopes: atoms with the same # of p+, but different #s of n0, and different masses Its like different flavors of each element Atoms with a too few or too many neutrons can exist for a while but can be unstable or radioactive The Nuclei of the 3 isotopes of Hydrogen

Comparing Isotopes Same: Different: Element (Lithium) Atomic # (3) # of p+ (3) # of e- (3) Different: Mass # (6, 7, 8) # of n0 (3, 4, 5)

Ions Ions: charged particles (+ or -) cations (X+) positive ions Form when an atom or molecule gains or loses e- cations (X+) positive ions anions (X–) negative ions To calculate the charge of an ion Compare the p+ & e- Charge = p+ – e-

Always the smaller # Always a whole # (no decimals) = number p+ Always the BIGGER # Usually a decimal = # p+ & n0

Symbols x Mass # Charge Atomic #

Atoms: by the NUMBERS Atomic #: unique for each element; gives elements their identity = # of p+ Mass #: whole # mass for a specific isotope; often written after element name (Krypton-84) = # of p+ + # of n0 Atomic Mass: weighted average mass of all isotopes of an element recorded as a decimal on the PT (periodic table)

Atoms: by the NUMBERS Protons = Atomic # Atomic Mass Protons = Atomic # change the #p+ change the element Neutrons = Mass # – Atomic # Electrons = # of p+ (for Atoms) For IONS: electrons = p+ - charge

The Standard Model Types of Particles: Video Clip: CERN: The Standard Model of Particle Physics Types of Particles: Quarks Leptons Electron Tau Muon Neutrinos Bosons: (force particles) Gluon Graviton photon (EM) Higgs strong force weak force Particles were organized by spin, charge, mass, and lifetime

Video Clip: Quarks: Inside the Atom Murray Gell-Mann found the name "quark" in the book “Finnegan's Wake" by James Joyce. The line "Three quarks for Muster Mark..." Gell-Mann received the 1969 Nobel Prize for his work in classifying elementary particles. Video Clip: Quarks: Inside the Atom 6 Types of Quarks: Up & Down Top & Bottom Charm & Strange

Finding the Quark Fermilab – National Particle Accelerator Lab Chicago IL

HADRONS Video Clip: Understanding the Standard Model Hadrons: particles composed of quarks Baryons Made of 3 quarks Protons & Neutrons are types of Baryons Mesons Made of 2 quarks (1 quark & 1 antiquark)