Notes

Outline

Atoms, Molecules, and Ions Part I-Intro To Atomic Structure and Periodicity

Basic Particles of Matter Atoms-smallest and most basic neutral particles of matter Molecules-Cluster of atoms held together by strong electrical forces called bonds that result in a stable neutral functioning particle of matter Ions-Charged atoms as a result of the loss or gain of electrons

Dalton’s Atomic Theory(1803) Based on Democritus Concept of the Atom Postulates 1. All matter composed of atoms 2. All atoms of a given element are chemically the same 3. Atoms of one element are different than atoms of another element 4. Matter reacts when molecules of matter fragment and recombine to form molecules of a new substance

Sub-Atomic Particles of the Atom Electron-negative particles of negligible but finite mass found in the periphery of atom Proton-Positive particles that are approximately 1800 times more massive than electron found in the nucleus of the atom Neutron-Neutral particle of approximately the same mass as the proton (slightly more massive)found in the nucleus

Properties of The Electron Initially thought to be Rays (Cathode Rays) JJ Thompson Cathode Ray Experiments(1897) Charged Plate deflection Shadow Cast Experiment Mass to Charge Ratio(1897) Millikan’s Oil Drop Experiment

T-2.4  Formation of Cathode Rays

T-8 Thompson’s Cathode Ray Experiment(1897)

T-2.6 Millikan’s Oil Drop Experiment

Properties of Proton Identified by Goldstein in 1897 Used perforated Cathode to generate particles Particles were deflected by a positive charged plate Protons are approximately 2000 times as massive as electrons

Properties of Neutron Identified by Chadwick in 1932 Used cloud chamber experiments to discover neutron Elusive because of its electrical neutrality

Three Radioactive Emissions Alpha Particle- Helium atom that is +2 charged Emitted by radioactive substances called alpha emitters Beta Particles- nuclear electron with the same mass and charge as the peripheral electrons Said to be half of a neutron Gamma Rays-Radiation of pure energy(very short wavelength)-Lethal

T-10 Alpha, Beta, and Gamma Rays

Nuclear Model of an Atom Rutherford’s Gold Foil Experiment Alpha Particle Scattering shows evidence of a nuclear atom

T-2.7 Alpha Particle Scattering From Metal Foils(macrocosmic view)

T-2.8 Molecular View of Alpha Scattering

Atomic Number and Mass Number of An Atom Atomic Number = number of protons in the nucleus of an atom Mass Number = Protons + Neutrons in nucleus of atom

Determining Sub Atomic               Particles From Nuclide Symbol Nuclide Symbol- Symbol of the element with the atomic number indicated as a subscript to the left of the symbol and the mass number indicated as a superscript to the left of the symbol For an neutral atom Atomic number = # protons #protons = # electrons # neutrons = Mass Number – Atomic Number Example

Isotopes Isotopes-two or more forms of an element whose atoms have the same number of protons and electrons but differ in the number of neutrons Isotopic name is the name of the element with mass number suffixed to it Carbon-12, Carbon-13 Oxygen-15, Oxygen-16, Oxygen-18 Protium, Deuterium, Tritium

Mendeleev’s Periodic Law The properties of the elements are a periodic function of their atomic masses Periodic function is the relationship between two variables where the value of one variable is repeated with a constant interval of the other Examples sin and cos function of right triangles Phases of the Moon

Moseley’s Periodic Law (Current) The properties of the elements are a periodic function of their atomic numbersPeriods and Groups Period- Row of elements in the Periodic Table(7) Beginning and ending of each period results in elements with similar properties Groups-vertical Column of elements(18) Elements within the same group have very similar properties

Metals, Non-Metals, and Metalloids Metal-elements whose atoms lose one or more electrons becoming Cations in order to become more stable Non-Metals-elements whose atoms gain one or more electrons becoming anions in order to become more stable Metalloids-elements whose atoms may lose or gain electrons depending upon what it is combined with

T-2.14 Periodic Table Showing Metals, Non-metals, and Metalloids

Locating elements in Groups and Periods Example