CHM 1210 1st Edition Lecture 4Outline of Last LectureI. Matter and Energy (con)a. Atomic Theoryb. Molecular Viewc. Coastd. Making Measurements e. Unit conversionsf. Temperture scalesOutline of Current Lecture II. Atoms, Ions and Molecules a. The Rutherford Model of Atomic StructureCurrent Outline2.1 The Rutherford Model of Atomic Structure Electrons In 1897, the English scientist J. J. Thomson (1856-1940) proposed that cathode rays must consist of _Tiny negatively charged particles of constant mass to charge ratio__, nowadays called _electrons. Deflection depends on: a. The strength of the deflecting magnetic or electric field_ b. __the size of the negative charged__ c. __the mass of the particle carrying the negative charge____ Charge-to-mass ratio: e/m = 1.758 820 x 108 C/g e = magnitude of the charge on the electron in Coulombs (C) m = mass of the electron (g) Ion = an atom or molecule that has _positive or negative charge Cation = a _positive_ charged ion (_1+, 2+, 3+__) (Notation for a charge)Anion = a Negative___ charged ion (__1-, 2-, 3-____) Electrons - Millikan’s oil drop experiment (1868-1953) showed that the charge of each oil drop was always __a whole # multiple_of a minimum charge, i.e., _the charge of one electron__. Millikan determined a. Charge of an electron : e- = _-1.602 x 10^-19c__ b. mass of an electron: me- = _9.109 x 10^-28__ These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• Thomson’s Plum-Pudding Model states that atoms consist of electrons distributed throughout _Massive positively charged, but very diffused sphere__. Radioactivity In 1886, the French physicist Henri Becquerel (1852-1908) discovered that some materials such as pitchblende produce invisible radiation, consisting of charged particles that can be detected using photographic plates. Definitions: - Radioactivity = the spontaneous emission of _high energy radiation_ and __particles___ by materials. -Beta particles (b) = a radioactive emission that is a high energy electron (1-)__ . -Alpha particle (a) = a radioactive emission with a charge of _2+_and a mass equivalent to that of a _Helium nucleus__. According to the Rutherford’s nuclear model of the atom, the nucleus: -Is a __positively charged center__ of an atom, containing nearly _all of the atoms mass___. -Is about __1/10,000___ the size of the atom. -Is surrounded by a __diffused cloud negatively charged electrons__. -Consists of two types of particles -Protons: _positive_ charged subatomic particles -Neutrons: __electrically neutral subatomic particles Obs: The atom is mostly __empty space___. Definition:Atomic mass unit (amu) or unified atomic mass units (u ) = a unit used to express the relative masses of atoms and subatomic particles that is exactly 1/12 the mass of 1 atom of carbon with 6protons and 6 neutrons in its nucleus. Obs: 1 amu = 1 Dalton (Da)= 1.66054 x 10^-27kg In 1912, Thomson and his research assistant, Francis W. Aston (1877-1945), constructed a positive-ray analyzer. The positive-ray analyzer experiment of Thomson and Aston demonstrated the existence of __isotopes (two different kinds of neon gas atoms)__. -90% = 20 amu -10% = 22 amu Definitions:Isotopes = atoms of an element containing the same # of protons but different # of _Neutrons____________. Nuclide = specific _isotope__ of an element. Dalton’s Atomic Theory defines an element as matter composed of ___identical atom_, all of which have the same _mass__. Rectification: An element is defined as matter composed of atoms, all having the same ____number or protons in the nucleus__. Atomic Mass= # of potons and neutrons A X Elemental symbol Z Atomic #= # of protons in the nucleus Obs: Z determines _identity_ of an element. Examples: Practice problem: Write symbols in the form for the nuclides that have 11 protons and 12 neutrons. -Collect and Organize: Z= 11 -Analyze: A= 11+12=23 -Solve: 23- 11NA Sodium- 23 •Think about It: Periodic table> Identity