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Date: 10-14-14 Day Plan: 1) Review Atomic Time Line 2) Notes on Atoms 3) Time to work on Homework Opener: 1) Which two sub-atomic particles have a charge? 2) Which two partials have essential the same mass? 3) Which Sub-atomic practical has a really small mass? Atoms, Molecules, and Ions Subatomic Particles • Protons and electrons are the only particles that have a charge. • Protons and neutrons have essentially the same mass. • The mass of an electron is so small we ignore it. Atoms, Molecules, and Ions • Monday – Notes • Tuesday – Candium Activity (Calculating Isotopes) • Wednesday – Answers to Candium Activity - Homework Due • Thursday – Video (For Sure Happening!) Atoms, Molecules, and Ions The Electron • Streams of negatively • charged particles were found to emanate from cathode tubes. • • J. J. Thompson is credited with their discovery (1897). The Atom, circa 1900: “Plum pudding” model, put forward by Thompson. Positive sphere of matter with negative electrons imbedded in it. Atoms, Molecules, and Ions The Nuclear Atom Discovery of the Nucleus Ernest Rutherford shot particles at a thin sheet of gold foil and observed the pattern of scatter of the particles. Since some particles were deflected at large angles, Thompson’s model could not be correct. Atoms, Molecules, and Ions The Nuclear Atom • Rutherford postulated a very small, dense nucleus with the electrons around the outside of the atom. • Most of the volume of the atom is empty space. • Protons were discovered by Rutherford in 1919. • Neutrons were discovered by James Chadwick Atoms, Molecules, in 1932. and Ions • Notes Over View A) Daltons Theory Of Atomic Mass B) Law of Chemistry C) Symbols of an Element D) Average Mass of an Isotope Atoms, Molecules, and Ions Notes : Atoms, Molecules, and Isotopes A) Daltons Atomic Theory of Matter • Idea proposed by John Dalton in the 19th century (1803) • Proposed the modern atomic theory Atoms, Molecules, and Ions Dalton’s Theory 1. Element are made up of extremely small particles called atoms. 2. All atoms of the same element have the same size, mass, and chemical properties. 3. Atoms cannot be created, divided into smaller particles or destroyed. 4. Different atoms combine in simple whole number ratios to form compounds. 2:1 5. In chemical reactions, atoms are separated, Atoms, combined or rearranged. Molecules, and Ions B) Laws of Chemistry Law of Definite Proportions 1) Elements combining to form a compound = always combine in definite proportions Example: sucrose (sugar) will always be 42.2% carbon, 6.50% hydrogen, and 51.30% oxygen 2) Percent by mass = mass of element x 100 mass of compound Atoms, Molecules, and Ions Example: • What is the percent by mass of carbon in sugar can if you have 211.0 g carbon in 500.0 g of sugar? Percent by mass = mass of element x 100 mass of compound Percent by Mass = 211.0 g X 100 = 500.0 g Atoms, Molecules, and Ions Example • What is the percent by mass of hydrogen in sugar cane if you have 32.5 g of hydrogen in 500 g of sugar cane? Percent by mass = mass of element x 100 mass of compound Percent by mass = 32.5 g x 100 = 500.0 g Atoms, Molecules, and Ions Law of Multiple Proportions Compounds can be composed of the same elements (with different masses) in whole number ratios. H2O • Example: The mass ratio of copper to chlorine in compound I is two times the mass ratio of copper to chlorine in compound II. Law of Conservation of Mass Mass at the beginning of a chemical Atoms, reaction = mass at the end of the reactionMolecules, and Ions C) Symbols of Elements Elements are symbolized by one or two letters. Atoms, Molecules, and Ions Atomic Number • All atoms of the same element have the same number of protons: • The atomic number (Z) Atoms, Molecules, and Ions Atomic Mass • The mass of an atom in atomic mass units (amu) • Mass = total number of protons and neutrons in the atom. Atoms, Molecules, and Ions Isotopes: • Atoms of the same element with different masses. • Isotopes have different numbers of neutrons. 11 C 6 12 C 6 13 C 6 14 C 6 Atoms, Molecules, and Ions Atomic Mass Atomic and molecular masses can be measured with great accuracy with a mass spectrometer. Atoms, Molecules, and Ions D) Average Mass (of an Isotope) • Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations. • Average mass is calculated from the isotopes of an element weighted by their relative abundances. (%) Atoms, Molecules, and Ions Example • Element X has two natural isotopes. The isotope with a mass of 10.012 amu (10X) has a relative abundance of 19.91%. The isotope with a mass of 11.009 amu (11X) has a relative abundance of 80.09%. Calculate the atomic mass of this element. 10X % 10X 10.012 .1991 (19.91/100) + 11X % 11X + 11.009 .8009 (80.09/100) = = Atoms, Molecules, and Ions Practice • Calculate the atomic mass of bromine. The two isotopes of bromine have atomic masses and relative abundance of 78.92 amu (50.69%) and 80.92 amu (49.31%. Atoms, Molecules, and Ions