AS Chemistry Unit 1

1
AS Chemistry Unit 1

• Weighing and Counting Atoms

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Atoms The Building Blocks of Matter

• Daltons Atomic Theory English school teacher
  John Dalton was the first to recognize that these
  laws and many experimental results could be
  explained by the existence of atoms.

3
Bell Work, 8/15/12

• Answer Question 1 on pg. 21.

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Statements of the Atomic Theory

• All matter is composed of extremely small
  particle called atoms.
• Atoms of a given element are identical in size,
  mass and other properties atoms of different
  elements differ in size, mass, and other
  properties.
• Atoms cannot be subdivided, created or destroyed.
• Atoms of different elements can combine in
  simple, whole-number ratios to form chemical
  compounds.
• In chemical reactions, atoms are combined,
  separated, or rearranged.

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Daltons Atomic Theory Contd

• Daltons theory has since been discarded it was
  the basis for further experiments because it
  successfully explained the Law of Conservation of
  Mass, Law of Definite Composition and other
  observations.

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Theory Updated

• We now know that atoms are divisible.
• We also know that an element can have atoms with
  differing masses these atoms are called isotopes.

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Theory Laws

• Law of Definite Composition by Mass states that a
  chemical compound contains the same elements in
  exactly the same proportions by mass regardless
  of the size of the sample.
• Law of Multiple Proportions states that If two or
  more different compounds are composed of the same
  two elements, the masses of the second element
  combined with a certain mass of the first element
  can be expressed as ratios of small whole numbers.

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• Example
• Carbon Monoxide CO
• Carbon Dioxide CO2
• Oxygen O2
• Ozone O3

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Atomic Numbers and Mass Numbers

• Atomic Number (Z) the number of protons in the
  nucleus of each atom of that element.
• Mass Number total number of protons and
  neutrons in the nucleus of an isotope.
• Nuclide the general term for any isotope of any
  element.

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Average Atomic Masses of Elements

• Average Atomic Mass the weighted average of the
  atomic masses of the naturally occurring isotopes
  of an element.
• Example Copper consists of
• 69.17 Cu-63 atomic mass 62.939 598 u
• 30.83 Cu-65 64.927 793 u
• (.6917)(62.939 598u) (.3083)(64.927 793u)
• 63.55 u (as seen on the periodic table)

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Average atomic mass equation

• aam (fa1)(m1) (fa2)(m2) etc
• aam average atomic mass
• fa fraction abundance of that specific isotope
• m mass of specific isotope

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Atomic Structure

• Protons subatomic particles that have a
  positive charge equal in magnitude to the
  negative charge of an electron and are present in
  atomic nuclei. Protons have a mass of 1.673 x
  10-24.
• Neutrons are electrically neutral subatomic
  particles found in atomic nuclei. The mass of a
  neutron is 1.675 x 10-24 g.
• Physicists have also found many other subatomic
  particles. However particles other than
  electrons, protons, and neutrons play little role
  in the properties of matter that are of interest
  in chemistry.

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Scientists

• Look up the following Scientists in your textbook
  and write what they were responsible for
  discovering and how they did it.
• Ernest Rutherford
• Sir John Joseph Thomson
• Robert Millikan (Oil Drop Experiment)

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Atomic mass the relative atomic mass of atoms
of that nuclide.

• The Mole, Avogadros Number, and Molar Mass
• mole the amount of a substance that contains
  the same number of particles as the number of
  atoms in exactly 12 g of carbon-12. Abbreviation
  is mol.
• Avogadros number 6.022 x 1023 the number of
  particles in exactly one mole of a pure
  substance.
• Molar mass the mass in grams of one mole of a
  pure substance.

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Molecules and Ions

• Molecule a collection of atoms held together by
  forces called covalent chemical bonds.
• Covalent chemical bonds caused by sharing
  electrons between atoms.
• Chemical formula a method of using symbols and
  subscripts to represent molecules.
• Structural formula symbols and lines are used
  to represent the shape of molecules

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Ions

• Ions an atom or groups of atoms that have a net
  positive or negative charge.
• Cation positively charged ion.
• Anion negatively charged ion.
• Ionic bonding force of attraction between
  oppositely charged ions.

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Copy the following questions and answer. Turn in
at the end of class

1. The element Boron, has an atomic mass of 10.81 u
   according to the periodic table. However, no
   single atom of boron has a mass of exactly 10.81
   u. How can you explain the difference?
2. How did the outcome of Rutherfords gold-foil
   experiment indicate the existence of a nucleus?

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Bell Work, 8/16/12

• Complete the Average Atomic Mass Worksheet for a
  grade.

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• List the number of protons, electrons and
  neutrons in the following
• a. Si-30
• b. Cr-52
• c. Sr 88
• d. Be-11
• FeO, Fe2O3, Fe3O4, represent what Law of matter?
• Tell which of Daltons principles of his Atomic
  Theory have been changed and why.

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• Convert the following to grams
• 1.22 mol sodium
• 14.5 mol copper
• 1.204 x1024 atoms lithium
• 6.046 x 1023 atoms bismuth
• Convert the following to atoms
• a. 64.1 grams aluminum
• b. 0.255 g sulfur
• c. 0.366 mol zinc
• d. 9.37 x 10-3 mol magnesium

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8/17/12

• Work on Exam style question 2 on pages 21 and 22.