The Atomic Theory of Matter and Numerical connections:

1
Chapter 2 3

• The Atomic Theory of Matter and Numerical
  connections

2
History of Atomic Theory
3
Structure of the atom
Protons- Found in nucleus Positive charge
(ve) Mass 1 Number of protons is known as the
Atomic number. Each element has a different
number of protons. Protons are made form quarks
and gluons.
Neutrons- Found in nucleus No charge Mass
1 Neutrons act to stabilise the nucleus and hold
the protons together with the strong force. The
Relative atomic mass is the number of protons
number of neutrons. Neutrons are made form quarks
and gluons.
Electrons- Found in (orbits) shells around the
nucleus. Each shell and sub-shell represent a
particular energy level that the electrons are
found at. These energy levels can be explained
by quantum mechanics. The number of electrons
equals the number of protons unless the atom
forms an ion.
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Isotopes

• Most elements form isotopes
• An Isotope is an element that has atoms that
  have a different number of neutrons.
• The RAM on the periodic table is an average for
  that element taking into account the abundance of
  the isotopes for that element.
• Isotope calculations are an important part of
  chemistry. Page 38 of your text gives you the
  formula and an example of these types of
  calculations.
• A mass spectrometer can be used to detect the
  presence and number of isotopes present in a
  sample of an element.

Mass Spectrometer
Mass spectrum of Bromine molecules
5
Shells and Sub Shells
6
The Mole

• The mole is a comparable measurement of elements
  and compounds used by chemists.
• Atoms are so small that an easier method of
  counting and comparing them was needed.
• The mole was developed based on the theory that
  exactly 12 grams of Carbon-12 has experimentally
  be determined to have 602000000000000000000000
  atoms.
• 6.02 x 1023 is known as Avagadros number.

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The mole continued...

• One mole (n) of any element is equal to its RAM
  and contains 6.02 x 1023 atoms of that element.
• For compounds the RAMs of the elements present
  are added together, known as the Molar Mass (M)
• Eg One mole of H2O 1 1 16 18 gmol-1
• In most cases you are not dealing with 1 mole of
  the chemical you are using!

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Mole calculations
n m M
Number of mol mass of chemical in grams divided
by its Molar Mass.
m n x M
Mass of a chemical in grams number of mol x
Molar mass.
M m n
Molar Mass of unknown chemical mass in grams
number of mole
Particles n x NA
Particles present number of mole x Avogadro's
number.
n Particles NA
Number of mole Particles present Avogadros
Number.
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Percentage composition

• Percentage composition tells us the amount by
  mass of each element present in a compound.

Molar mass (39.1 x 2) (52 x 2) (16 x 7)
294.2 gmol-1 Oxygen (16 x
7) x 100 294.2
1 38
10
Empirical formula

• The simplest whole number ratio of atoms present
  in a compound.
• H2O
• C2H3O4
• C6H12O6
• You must be able to perform calculations to
  determine empirical formula.
• Refer to page 59-60 of text for method and
  examples.

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Molecular formula

• The molecular formula is the actual formula of a
  chemical which is not always in its simplest form
  (empirical formula)
• Glucose has the molecular formula C6H12O6.
• Its Empirical formula is CH2O.
• An explanation and examples of calculations of
  Molecular formula are found on pages 61 63 of
  your text book.

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What do I need to be able to work out?

• Electron arrangement really important
• Number of mole most important
• Mass from number of mole also important
• Particles present using NA not used much
• composition not used much
• Empirical formula important
• Molecular formula - important

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Stressed?
The faster the circles move the
more stressed you are. If they
dont move you are either very relaxed or dead.

If this last chapter is doing your head in please
stick with it. Lots of Chemistry students dont
really get this stuff until year 12 or even
Uni. It will be revised heaps and is repeated in
Unit 2, 3 and 4.