Slide 1

Slide 2 Atoms, Molecules, and Ions Slide 3 Chemistry Timeline #1 B.C. 400 B.C. Demokritos and Leucippos use the term "atomos 1500's Georg Bauer: systematic metallurgy Paracelsus: medicinal application of minerals 1600's Robert Boyle:The Skeptical Chemist. Quantitative experimentation, identification of elements 1700s' Georg Stahl: Phlogiston Theory Joseph Priestly: Discovery of oxygen Antoine Lavoisier: The role of oxygen in combustion, law of conservation of mass, first modern chemistry textbook 2000 years of Alchemy Slide 4 Chemistry Timeline #2 1800's Joseph Proust: The law of definite proportion (composition) John Dalton: The Atomic Theory, The law of multiple proportions Joseph Gay-Lussac: Combining volumes of gases, existence of diatomic molecules Amadeo Avogadro: Molar volumes of gases Jons Jakob Berzelius: Relative atomic masses, modern symbols for the elements Dmitri Mendeleyev: The periodic table J.J. Thomson: discovery of the electron Henri Becquerel: Discovery of radioactivity 1900's Robert Millikan: Charge and mass of the electron Ernest Rutherford: Existence of the nucleus, and its relative size Meitner & Fermi: Sustained nuclear fission Ernest Lawrence: The cyclotron and trans-uranium elements Slide 5 Laws Conservation of Mass Law of Definite Proportion compounds have a constant composition. They react in specific ratios by mass. Multiple Proportions- When two elements form more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers. Slide 6 Proof Mercury has two oxides. One is 96.2 % mercury by mass, the other is 92.6 % mercury by mass. Show that these compounds follow the law of multiple proportion. Speculate on the formula of the two oxides. Slide 7 Daltons Atomic Theory (1808) Atoms cannot be subdivided, created, or destroyed Atoms of different elements combine in simple whole-number ratios to form chemical compounds In chemical reactions, atoms are combined, separated, or rearranged All matter is composed of extremely small particles called atoms Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties John Dalton Slide 8 Modern Atomic Theory Several changes have been made to Daltons theory. Dalton said: Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties Modern theory states: Atoms of an element have a characteristic average mass which is unique to that element. Slide 9 Modern Atomic Theory #2 Dalton said: Modern theory states: Atoms cannot be subdivided, created, or destroyed Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these changes CAN occur in nuclear reactions! Slide 10 Discovery of the Electron In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle. Cathode ray tubes pass electricity through a gas that is contained at a very low pressure. Slide 11 Thomsons Atomic Model Thomson believed that the electrons were like plums embedded in a positively charged pudding, thus it was called the plum pudding model. Slide 12 Rutherfords Gold Foil Experiment Alpha particles are helium nuclei Particles were fired at a thin sheet of gold foil Particle hits on the detecting screen (film) are recorded Slide 13 Atomic Particles ParticleChargeMass (kg)Location Electron9.109 x 10 -31 Electron cloud Proton+11.673 x 10 -27 Nucleus Neutron01.675 x 10 -27 Nucleus Slide 14 The Atomic Scale Most of the mass of the atom is in the nucleus (protons and neutrons) Electrons are found outside of the nucleus (the electron cloud) Most of the volume of the atom is empty space q is a particle called a quark Slide 15 About Quarks Protons and neutrons are NOT fundamental particles. Protons are made of two up quarks and one down quark. Neutrons are made of one up quark and two down quarks. Quarks are held together by gluons Slide 16 Isotopes Isotopes are atoms of the same element having different masses due to varying numbers of neutrons. IsotopeProtonsElectronsNeutronsNucleus Hydrogen1 (protium) 110 Hydrogen-2 (deuterium) 111 Hydrogen-3 (tritium) 112 Slide 17 Atomic Masses IsotopeSymbolComposition of the nucleus % in nature Carbon-12 12 C6 protons 6 neutrons 98.89% Carbon-13 13 C6 protons 7 neutrons 1.11% Carbon-14 14 C6 protons 8 neutrons