CHEMISTRY The Molecular Science Chapter two

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CHEMISTRYThe Molecular ScienceChapter two

• Slides prepared by
• S. Michael Condren
• Department of Chemistry
• Christian Brothers University

to Accompany CHEMISTRY The Molecular Science by
John W. Moore, Conrad Stanitski, Peter C. Jurs
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Chapter 2

• Elements Atoms

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Atomic Structure

• Electrical charges of the same type repel one
  another, and charges of the opposite type attract
  one another.

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Radioactivity
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Alpha Radiation

• composed of 2 protons and 2 neutrons
• thus, helium-4 nucleus
• 2 charge
• mass of 4 amu
• creates element with atomic number 2 lower

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Beta Radiation

• composed of a high energy electron which was
  ejected from the nucleus
• neutron converted to proton
• very little mass
• -1 charge
• creates element with atomic number 1 higher

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Gamma Radiation

• nucleus has energy levels
• energy released from nucleus as the nucleus
  changes from higher to lower energy levels
• no mass
• no charge

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Structure of the Atom

• electrons
• found in electron cloud
• relative charge of -1
• relative mass of 0.00055 amu

• protons
• found in nucleus
• relative charge of 1
• relative mass of 1.0073 amu
• neutrons
• found in nucleus
• neutral charge
• relative mass of 1.0087 amu

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Millikans Experiment
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Rutherfords Experiment
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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

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Ions

• charged single atom
• charged cluster of atoms

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Ions

• cations
• positive ions
• anions
• negative ions
• ionic compounds
• combination of cations and anions
• zero net charge

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Metric Prefixes
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Relative size of atom and atomic nucleus
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Scanning Tunneling Microscope
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Measurement and Units

• length - meter
• volume - liter
• mass - gram

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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

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Isotopes

• atoms of the same element which differ in the
  number of neutrons in the nucleus
• designated by mass number

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Isotopes of Hydrogen H-1, 1H, protium

• 1 proton and no neutrons in nucleus
• only isotope of any element containing no
  neutrons in the nucleus
• most common isotope of hydrogen

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Isotopes of Hydrogen H-2 or D, 2H, deuterium

• 1 proton and 1 neutron in nucleus

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Isotopes of Hydrogen H-3 or T, 3H, tritium

• 1 proton and 2 neutrons in nucleus

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Mass Number, A

• integer representing the approximate mass of an
  atom
• equal to the sum of the number of protons and
  neutrons in the nucleus

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Nuclear Notation

• X-A
• C-12
• XA
• C12
• ZXA
• 6C12

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Masses of Atoms

• Carbon-12 Scale
• Masses of the atoms are compared to the mass of
  C-12 isotope having a mass of 12.0000

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Mass Spectrometer
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Atomic Masses andIsotopic Abundances

• natural atomic masses
• sum(atomic mass of isotope)
• ? (fractional isotopic abundance)

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The Mole

• a unit of measurement, quantity of matter present
• Avogadros Number
• 6.022 ? 1023 particles
• Latin for pile

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Molar Mass

• Sum
• atomic masses
• represented by formula
• atomic masses ? gaw
• molar mass ? MM

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Example

• How many grams of Cu are there in 5.67 mol Cu?
• g Cu (5.67 mol)(63.546g/mol)
• 360. g

Atomic mass of Cu
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Example

• Calculate the number of boron atoms in 1.000g
  sample of the element.
• B atoms (1.000g)(1mol / 10.81g)
• ? (6.022 ? 1023atoms/mol)
• 5.571 ? 1022 B atoms

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Example

• How many moles of silicon, S, are in 30.5g of S?
• mol Si (30.5g)(1 mol/32.06g)
• 0.951 mol Si

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Example

• What is the molar mass of methanol, CH3OH?
• MM 1(gaw)C (3 1)(gaw)H 1(gaw)O
• 1(12.011)C 4(1.00794)H 1(15.9994)O
• 22.042 g/mol

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Example

• How many moles of carbon dioxide molecules are
  there in 6.45g of carbon dioxide?
• MM 1(gaw)C 2(gaw)O 44.01 g/mol
• mol CO2 (6.45g)(1 mol/44.01g)
• 0. 147 mol

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Development of Periodic Table

• Newlands - English
• 1864 Law of Octaves every 8th element
  has similar properties

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Development of Periodic Table

• Mendeleev
• Russian
• 1869 - Periodic Law
• allowed him to predict properties of unknown
  elements

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Mendeleevs Periodic Table

• the elements are arranged according to
  increasing atomic weights
• Missing elements 44, 68, 72, 100 amu

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Predicted Properties of Ekasilicon
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Modern Periodic Table

• Moseley, Henry Gwyn Jeffreys
• 18871915, English physicist.
• studied the relations among spectra of different
  elements.
• concluded that the atomic number is equal to the
  charge on the nucleus based on the x-ray spectra
  emitted by the element.
• explained discrepancies in Mendeleevs Periodic
  Law.

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Modern Periodic Table

• the elements are arranged according to increasing
  atomic numbers

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Periodic Table of the Elements
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Organization of Periodic Table

• period horizontal row
• group vertical column

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Family Names

• Group IA alkali metals
• Group IIA alkaline earth metals
• Group VIIA halogens
• Group VIIIA noble gases
• transition metals
• inner transition metals
• lanthanum series rare earths
• actinium series trans-uranium series

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Types of Elements

• metals
• nonmetals
• metalloids semimetals