Presentation on theme: "Dr. S. M. Condren Chapter 2 Atoms and Elements. Dr. S. M. Condren Daltons Atomic Theory Postulates proposed in 1803 know for first exam."— Presentation transcript:
Dr. S. M. Condren Chapter 2 Atoms and Elements
Dr. S. M. Condren Daltons Atomic Theory Postulates proposed in 1803 know for first exam
Dr. S. M. Condren Daltons Atomic Theory Postulate 1 An element is composed of tiny particles called atoms. All atoms of a given element show the same chemical properties.
Dr. S. M. Condren Daltons Atomic Theory Postulate 2 Atoms of different elements have different properties.
Dr. S. M. Condren Daltons Atomic Theory Postulate 3 Compounds are formed when atoms of two or more elements combine. In a given compound, the relative number of atoms of each kind are definite and constant.
Dr. S. M. Condren Daltons Atomic Theory Postulate 4 In an ordinary chemical reaction, no atom of any element disappears or is changed into an atom of another element. Chemical reactions involve changing the way in which the atoms are joined together.
Dr. S. M. Condren Structure of the Atom Composed of: protons neutrons electrons protons –found in nucleus –relative charge of +1 –relative mass of amu
Dr. S. M. Condren Structure of the Atom Composed of: protons neutrons electrons neutrons –found in nucleus –neutral charge –relative mass of amu
Dr. S. M. Condren Structure of the Atom Composed of: protons neutrons electrons –found in electron cloud –relative charge of -1 –relative mass of amu
Dr. S. M. Condren ATOM COMPOSITION protons and neutrons in the nucleus. the number of electrons is equal to the number of protons in a neutral atom. electrons in space around the nucleus. extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. The atom is mostly empty space
Dr. S. M. Condren Radioactivity Alpha – helium-4 nucleus Ra 226 Rn He 4 ( ) Beta – high energy electron U 239 Np Gamma – energy resulting from transitions from one nuclear energy level to another Ni 60* Ni 60 +
Dr. S. M. Condren Penetrations of Radioactive Emissions
Dr. S. M. Condren Isotopes & Their Uses Heart scans with radioactive technetium Tc Emits gamma rays
Dr. S. M. Condren The modern view of the atom was developed by ( ). The modern view of the atom was developed by Ernest Rutherford ( ).
Dr. S. M. Condren Rutherfords Model of the Atom atom is composed mainly of vacant space all the positive charge and most of the mass is in a small area called the nucleus electrons are in the electron cloud surrounding the nucleus
Dr. S. M. Condren Nucleus If nucleus is 1 The atom would be 1.5 miles in diameter
Dr. S. M. Condren Ions Ion –electrostatically charged atom or group of atoms cations –positive ions anions –negative ions ionic compounds –combination of cations and anions –zero net charge
Dr. S. M. Condren Atomic number, Z the number of protons in the nucleus the number of electrons in a neutral atom the integer on the periodic table for each element 13 Al Atomic number Atom symbol Atomic weight
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Dr. S. M. Condren Which best represents the poles?
Dr. S. M. Condren Quantum Corral
Dr. S. M. Condren, Mass Number, A C atom with 6 protons and 6 neutrons is the mass standard = 12 atomic mass units (u) Mass Number (A) = # protons + # neutrons A boron atom can have A = 5 p + 5 n = 10 u
Dr. S. M. Condren Isotopes atoms of the same element which differ in the number of neutrons in the nucleus designated by mass number
Dr. S. M. Condren Isotopes of Hydrogen H-1, 1 H, protium 1 proton and no neutrons in nucleus only isotope of any element containing no neutrons in the nucleus most common isotope of hydrogen
Dr. S. M. Condren Isotopes of Hydrogen H-2 or D, 2 H, deuterium 1 proton and 1 neutron in nucleus
Dr. S. M. Condren Isotopes of Hydrogen H-3 or T, 3 H, tritium 1 proton and 2 neutrons in nucleus radioactive electron antineutrino
Dr. S. M. Condren The radioactive isotope 14 C has how many neutrons? 6, 8, other
Dr. S. M. Condren The identity of an element is determined by the number of which particle? protons, neutrons, electrons
Dr. S. M. Condren Mass Spectrometer a simulation is available at
Dr. S. M. Condren Mass spectrum of C 6 H 5 Br
Dr. S. M. Condren Atomic Masses and Isotopic Abundances natural atomic masses = SUM[(atomic mass of isotope) *(fractional isotopic abundance)]
Dr. S. M. Condren Example: Chlorine has two isotopes, Cl-35 and Cl-37, which have masses of and amu, respectively. The natural atomic mass of chlorine is amu. What are the percent abundances of the two isotopes? let x = fraction Cl-35y = fraction Cl-37 x + y = 1y = 1 - x (AW Cl-35)(fraction Cl-35) + (AW Cl-37)(fraction Cl-37) = Thus: *x *y = *x *(1-x) = x = % Cl-35 Thus % Cl-37
Dr. S. M. Condren Molar Mass-Molecular Weight Sum atomic masses represented by formula atomic masses => gaw molar mass => MM
Dr. S. M. Condren Example What is the molar mass of ethanol, C 2 H 5 O 1 H 1 ? MM = 2(gaw) C + (5 + 1)(gaw) H + 1(gaw) O = 2(12.011) C + 6( ) H + 1( ) O = = g/mol Significant figures rule for multiplication Significant figures rule for addition Sequence – multiplication then addition, apply significant figure rules in proper sequence
Dr. S. M. Condren The Mole a unit of measurement, quantity of matter present Avogadros Number x particles Latin for pile
Dr. S. M. Condren One Mole of each Substance Clockwise from top left: 1-Octanol, C 8 H 17 OH; Mercury(II) iodide, HgI 2 ; Methanol, CH 3 OH; and Sulfur, S 8.
Dr. S. M. Condren Example How many moles of carbon dioxide molecules are there in 10.00g of carbon dioxide? MM = 1(gaw)C + 2(gaw)O = g/mol #mol CO 2 = (10.00g) (1 mol/44.01g) / = mol
Dr. S. M. Condren Missing elements: 44, 68, 72, & 100 amu Mendeleevs Periodic Table
Dr. S. M. Condren Properties of Ekasilicon
Dr. S. M. Condren Modern Periodic Table the elements are arranged according to increasing atomic numbers
Dr. S. M. Condren Periodic Table of the Elements
Dr. S. M. Condren Organization of Periodic Table period - horizontal row group - vertical column Family Names Group IAalkali metals Group IIAalkaline earth metals Group VIIAhalogens Group VIIIAnoble gases transition metals inner transition metals –lanthanum seriesrare earths –actinium seriestrans-uranium series
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ELEMENTS THAT EXIST AS MOLECULES Allotropes of C
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ELEMENTS THAT EXIST AS DIATOMIC MOLECULES
Dr. S. M. Condren White P 4 and polymeric red phosphorus S 8 sulfur molecules ELEMENTS THAT EXIST AS POLYATOMIC MOLECULES