unit 1 – atomic structure bravo – 15,000 kilotons

Unit 1 Atomic StructureBravo 15,000 kilotons

Chemistry Timeline #1B.C. 400 B.C. Democritos and Leucippos use the term "atomos1500's Georg Bauer: systematic metallurgy Paracelsus: medicinal application of minerals

1600'sRobert 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

Chemistry Timeline #21800'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

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

Modern Atomic TheorySeveral 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 propertiesModern theory states:Atoms of an element have a characteristic average mass which is unique to that element.

Modern Atomic Theory #2Dalton 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!

Modern Atomic Theory Atoms of an element have a characteristic average mass which is unique to that element. Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these changes CAN occur in nuclear reactions! All matter is composed of atoms Atoms of any one element differ in properties from atoms of another element

Discovery of the ElectronIn 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.

Conclusions from the Study of the Electron Cathode rays have identical properties regardless of the element used to produce them. All elements must contain identically charged electrons. Atoms are neutral, so there must be positive particles in the atom to balance the negative charge of the electrons Electrons have so little mass that atoms must contain other particles that account for most of the mass

Thomsons Atomic ModelThomson believed that the electrons were like plums embedded in a positively charged pudding, thus it was called the plum pudding model.

Mass of the Electron1909 Robert Millikan determines the mass of the electron.The oil drop apparatusMass of the electron is 9.109 x 10-31 kg

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

Try it Yourself!In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target?

The AnswersTarget #1Target #2

Rutherfords Findings The nucleus is small The nucleus is dense The nucleus is positively charged Most of the particles passed right through A few particles were deflected VERY FEW were greatly deflectedLike howitzer shells bouncing off of tissue paper!

Conclusions:

Atomic Particles

ParticleChargeMass #LocationElectron-10 Electron cloudProton+11 NucleusNeutron01 Nucleus

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 spaceq is a particle called a quark

About QuarksProtons 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

Atomic NumberAtomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.

Element# of protonsAtomic # (Z)Carbon66Phosphorus1515Gold7979

Mass NumberMass number is the number of protons and neutrons in the nucleus of an isotope.Mass # = p+ + n0881818Arsenic753375Phosphorus153116

Nuclidep+n0e-Mass #Oxygen - 10 - 3342 - 3115

Isotopes Isotopes are atoms of the same element having different masses due to varying numbers of neutrons.

Isotope ProtonsElectronsNeutronsNucleusHydrogen1 (protium) 110Hydrogen-2 (deuterium)111Hydrogen-3 (tritium)112

Atomic MassesAtomic mass is the average of all the naturally isotopes of that element.Carbon = 12.011

IsotopeSymbolComposition of the nucleus% in natureCarbon-1212C6 protons 6 neutrons98.89%Carbon-1313C6 protons 7 neutrons1.11%Carbon-1414C6 protons 8 neutrons