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Chapter 2 Atoms, Molecules and Ions Pentacene on a copper surface (AFM image) Science, Volume 325,...
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Transcript of Chapter 2 Atoms, Molecules and Ions Pentacene on a copper surface (AFM image) Science, Volume 325,...
![Page 1: Chapter 2 Atoms, Molecules and Ions Pentacene on a copper surface (AFM image) Science, Volume 325, Issue 5944, pp. 1110 – 1114 (28 August 2009).](https://reader033.fdocuments.net/reader033/viewer/2022050819/56649ee75503460f94bf766d/html5/thumbnails/1.jpg)
Chapter 2
Atoms, Molecules and Ions
Pentacene on a copper surface (AFM image)
Science, Volume 325, Issue 5944, pp. 1110 – 1114 (28 August 2009).
![Page 2: Chapter 2 Atoms, Molecules and Ions Pentacene on a copper surface (AFM image) Science, Volume 325, Issue 5944, pp. 1110 – 1114 (28 August 2009).](https://reader033.fdocuments.net/reader033/viewer/2022050819/56649ee75503460f94bf766d/html5/thumbnails/2.jpg)
(Dalton’s) Atomic Theory• Each element is made up of atoms.
• Atoms of a given element are identical while atoms of different elements differ.
• Chemical compounds are made up of specific whole number ratios of atoms.
• Chemical Reactions involve the reorganization of atoms – atoms (and masses) do not change.
John Dalton, 1766 -1844 Lithograph
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Properties of Charged Particles
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Thomson was awarded the 1906 Nobel Prize.
Sir Joseph John Thompson, 1856 - 1940
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Electron mass/charge = -5.6857 x 10-9 g coulomb-1
An evacuated tube, containing a small amount of a gas was attached to a power supply:
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• The same cathode rays (electrons) were seen no matter what gas the tube was filled with.
• But the positively charged portion left over had a different mass/charge dependent on the type of gas used.
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Thompson’s Conclusion:
Electrons are a fundamental unit of all materials, and atoms look like a “sea” of positive charge with imbedded electrons:
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Millikan’s Oil Drop Experiment
Determined the charge on an electron = 1.592 X 10-19 coulombs
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•γ-rays are high-energy light.
•α-particles are helium
nuclei.
•β-particles are high energy
electrons
Types of Radiation(Marie Curie/Rutherford)
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Marie Curie1867-1934
•Met Pierre Curie, Physics Professor at the Sorbonne in 1894
•Succeeded her husband as Head of the Physics Laboratory at the Sorbonne
•Following the death of Pierre Curie in 1906, she took his place as Professor of General Physics in the Faculty of Sciences, the first time a woman had held this position.
•Received the Nobel Prize for Physics in 1903
•Received a second Nobel Prize in Chemistry in 1911
•Discovered two elements (Polonium and Radium)
![Page 11: Chapter 2 Atoms, Molecules and Ions Pentacene on a copper surface (AFM image) Science, Volume 325, Issue 5944, pp. 1110 – 1114 (28 August 2009).](https://reader033.fdocuments.net/reader033/viewer/2022050819/56649ee75503460f94bf766d/html5/thumbnails/11.jpg)
Marie Curie(Maria Sklodowska)
1867-1934
•Met Pierre Curie, Physics Professor at the Sorbonne in 1894
•Succeeded her husband as Head of the Physics Laboratory at the Sorbonne
•Following the death of Pierre Curie in 1906, she took his place as Professor of General Physics in the Faculty of Sciences, the first time a woman had held this position.
•Received the Nobel Prize for Physics in 1903
•Received a second Nobel Prize in Chemistry in 1911
•Discovered two elements (Polonium and Radium)
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Rutherford’s Gold Foil Experiment
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The Composition of the Atom
The nucleus is made up of protons and neutrons
Rutherfordprotons 1919
James Chadwickneutrons 1932
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The “Modern” Atom
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Particle Mass Charge
g amu Coulombs (e)
Electron 9.109 x 10-28 (0) –1.602 x 10-19 –1Proton 1.673 x 10-24 1 +1.602 x 10-19 +1Neutron 1.675 x 10-24 1 0 0
The Fundamental Particles
Atoms are uncharged species – thus they contain the same number of protons and electrons (charged species are known as ions)
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The Concept of Atomic Number
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The Concept of Atomic Number
The atomic number (Z) = # of protons
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The Concept of Atomic Number
The atomic number (Z) = # of protons
The atomic mass (A) = protons + neutrons
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Atomic Mass Units
The atomic mass (A) = protons + neutrons
• Mass of carbon-12 = 1.9926 X 10-23
g
• Mass of carbon-12 = 12 amu (atomic mass units - amu or u)
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Isotopic Distributions
Why does the periodic table say that the mass of carbon is 12.011 amu?
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Isotopic Distributions
Why does the periodic table say that the mass of carbon is 12.011 amu?
98.9% of all carbon atoms have A = 12 (6 neutrons)
1.1% of all carbon atoms have A = 13 (7 neutrons)
12.011 is the average mass of a large sample of carbon atoms. When we measure “large” amounts of atoms, we can always use the average atomic mass.
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Mass Spectromeric Isotope Indentification
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Mass Spectrometric Isotope Identification
200Hg
202Hg
201Hg
199Hg
198Hg
196Hg
204Hg
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How many atoms are in 1 g of copper?
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How many atoms are in 1 g of copper? If Cu has an atomic mass of 63.546 amu, how does this easily convert to grams?
Avogadro’s Number (the mole) relates atomic mass to sample mass:
NA = 6.022 X 1023 = 1 mole
1 mole of atoms = mass in grams equal to the atomic mass
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How many atoms are in 1 g of copper? If Cu has an atomic mass of 63.546 amu, how does this easily convert to grams?
Avogadro’s Number (the mole) relates atomic mass to sample mass:
NA = 6.022 X 1023 = 1 mole
1 mole of atoms = mass in grams equal to the atomic mass
The molar mass, M, is the mass of one mole of a substance.
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A charged species is called an ion.
Metals tend to lose electrons to form positively charged ions – cations.
Nonmetals tend to gain electrons to form negatively charged ions – anions.
When forming compounds, the metal and nonmetal ions combine so that the net charge on a formula unit is zero.
Ions and Ionic Compounds
The atomic charge = protons – electrons
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Ions and Ionic Compounds
Ionic compounds are held together by the electrostatic attraction of opposite charges - this is also known as coulombic attraction. This attraction is an ionic bond.
Ionic compounds behave as an aggregate, not individual molecules
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Predicting Ionic Charges
Main group elements tend to lose or gain electrons in order to equal the electron count of the nearest noble gas
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Predicting Ionic Charges
Main group elements tend to lose or gain electrons in order to equal the electron count of the nearest noble gas
Transition Metals Are Able To Form Multiple Cations: +1, +2, +3 and/or +4