Transcript Slide 1
Take out reading check andDo 1. If 100,000,000 Now: copper atoms were placed side by side, they would form a line 1 cm long. A)What is the number of atoms written in scientific notation. B)What is the diameter of 1 copper atom? 0.0000001 cm So how small is the atom? •Very small! • Smallest particle of an element that keeps the element’s properties About 400 B.C. Democritus • a Greek philosopher • Proposed matter was composed of tiny, indivisible particles called “atomos” • origin of the word atom Late 1700’s Antoine Lavoisier Proposed Law of Conservation of Matter matter cannot be created nor destroyed Joseph Proust Proposed Law of Definite Composition - a given compound always contains the same elements in the same proportions by mass John Dalton’s Atomic Theory • Each element is composed of tiny indivisible particles called atoms. The atoms of any one element differ from those of any other element. • Atoms of different element combine in simple whole-number ratios to form compounds. • In chemical reactions, atoms are neither created nor destroyed. Atoms are rearranaged. Late 1800’s J.J. Thomson • Experimented with cathode ray tubes (CRTs) -______ +______ Cathode + Battery Anode J. J. Thomson • Concluded cathode ray composed of negative particles - electrons • Unable to measure mass of electron, but found ratio of electron’s electrical charge to 8 its mass - 1.76 x 10 Coulombs/gram + • Proposed Plum Pudding Model - + + + + - + - + - DO NOW! • What were Dalton’s and Thompson’s contributions to atomic theory? Robert Millikan • Performed Oil Drop Experiment in 1909 • Found charge of electron to be 1.6 x 10 -19 Coulombs -28 • Calculated mass of electron to be ~ 9.1 x 10 g Radioactivity • In 1896, Henri Becquerel accidentally discovered radioactivity while studying uranium salts • Spontaneous emission of energy from unstable nuclei •One type of radiation is alpha radiation. It is positively charged. Ernest Rutherford in 1909 • Performed Alpha Particle Scattering Gold Foil Experim • Findings ??? 1. Atoms mostly empty space 2. Atom contains a nucleus 3. Nucleus positively charged What else is in the atom? Proton – Discovered by Rutherford in 1918 by Neutron - Discovered by Chadwick in 1932 Do NOW! 1. What is an atom? 2. What subatomic particles does it contain? 3. Distinguish between the subatomic particles. 4. What is an isotope? 5. What is an ion? Atoms are the smallest particle of an element that retains its properties. Atoms contain… Subatomic Particle Proton Location in Atom In nucleus Electron Outside nucleus, in energy levels (clouds) Neutron In nucleus Charge Mass Positive Similar to the neutron Negative Very small compared to proton Neutral 99.9% of mass Isotopes • Are a different form of the atom that have the same number of protons in nucleus but a different number of neutrons. • Their masses vary • Chemically behaves the same, may affect radioactivity Ions • Are atoms that have lost or gained electrons to become stable • Atoms that lose electrons are positively charged ( # protons > # electrons) • Atoms that gain electrons are negatively charge ( # protons < # electrons) Using the Periodic Table and the information below, determine how many subatomic particles (protons, electron, and neutrons) are in… a. 25Mg2+ Try your best!!! b. Calcium – 40 c. 76Ge Mass number (must be provided) =p+n 25Mg 2+ 12 Atomic number (on periodic table) = p (also e if not charged) Charge = p - e •Calcium - 40 Mass number Fill in please Symbol # Protons # Electrons # Neutrons Charge 14 1+ 80Br 60Co2+ 11 7 10 15 Do Now… • Becky earned the following quiz grades… 87, 56, 94, 88 and 80. What is her quiz average? • Becky’s HW average was a 55 and her test average was a 75. Her teacher based her overall class grade on the following percentages: HW is 20%, Quiz is 50%, and Test is 30%. What is her overall grade in this class? Standard: Carbon-12 • This isotope of carbon was assigned a mass of exactly 12 amu • 1 amu (atomic mass unit) = 1/12 the mass of a carbon-12 atom • Carbon-12 has 6 protons and 6 neutrons • The mass of the proton is about 1 amu • The mass of the neutron is about 1 amu Since each isotope of given element has different masses, the atomic mass is an average • Chlorine has two naturally occuring isotopes. Chlorine-35 has a mass of 34.969 amu and chlorine-37 has a mass of 36.966 amu. • Chlorine-35 has a natural abundance of 75.77% and chlrorine-37 has a natural abundance of 24.23. • What is atomic mass of chlorine?