Everything is made of Atoms

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Everything is made of Atoms
-Richard Feynman

• Review of scientific notation
• A brief history of the atom
• Composition of Earths crust
• Avagadros Number
• How many atoms are in your body?

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How many seconds are in a year?
60?60?24?365 31536000
3.1536?107
3.15?107 (to 3 significant digits)
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How many years are in a second?
1/3.1536 x 107 0.0000000317098
3.17098?10-8
3.17?10-8 (to 3 significant digits)
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How many atoms are in my body?
?
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A brief history of the atom
In the 5th cent. B.C. the Greek philosophers
Democritus and Leucippus proposed that matter was
made up of tiny, indivisible particles in
constant motion. Aristotle, however, did not
accept the theory, and it was ignored for
centuries.
atoma non-divisible
http//www.neutron.anl.gov/hyper-physics/histatom.
html
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A brief history of the atom
Modern atomic theory began with the publication
in 1808 by British chemist and physicist John
Dalton of his experimental conclusions that 1.
all atoms of an element have the same size and
weight, and 2. atoms of elements unite
chemically in simple numerical ratios to form
compounds.
http//www.neutron.anl.gov/hyper-physics/histatom.
html
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Definition Element
A single or isolated group of particles composed
of only one species of atoms.
sulfur
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A brief history of the atom
In 1897, British physicist J.J. Thomson
discovered the electron, a subatomic particle
(i.e., a particle smaller than the atom). For
this work, he was awarded a Nobel prize in 1906.
His discovery of the electron led to Thomsons
proposed plum-pudding model for the atom.
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A brief history of the atom
In 1911, New Zealander Ernest Rutherford
explained an atom's structure in terms of a
positively charged nucleus surrounded by
negatively charged electrons orbiting around it.
http//www.neutron.anl.gov/hyper-physics/histatom.
html
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Perspective on the atom If the nucleus could be
enlarged to the size of a pea and placed at the
centre of a football stadium, the electrons would
be like flies buzzing around the cheap seats.
http//www.mgreen.com/stadpages/stad10.html
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A brief history of the atom
In 1913 Danish physicist Neils Bohr used quantum
theory to explain why electrons could remain in
certain allowed orbits without radiating energy.

Bohr model for the atom.
http//www.neutron.anl.gov/hyper-physics/histatom.
html
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Modern view of the atom
Atom (definition) The smallest unit of matter
that possesses the properties of an element.
Nucleus (not to scale)
Electrons (clouds)
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Modern view of the atom

• Atoms are composed of subatomic particles
  protons, neutrons and electrons.
• Protons and neutrons reside in the nucleus of
  the atom - the central core where virtually all
  of the mass of the atom is located.
• Electrons exist outside the atomic nucleus in a
  cloud of orbitals.

Nucleus (not to scale)
Electrons (clouds)
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Important characteristics of the electron

• they orbit the nucleus in a cloud (or shell)
• they are bound to atoms because their negative
  charge is attracted to the positive charge in the
  nucleus
• the chemical behaviour of atoms and elements is
  largely controlled by the number and
  configuration of electrons

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Physical facts of subatomic particles
There are actually a lot more known subatomic
particles than those listed here
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How many elements are there in the world?

• At this time, scientists know of 116 different
  elements, of which 92 occur in nature (the rest
  are man-made).
• The naming convention for new elements is to
  name them after people or places (e.g.,
  Einsteinium or Gallium).

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How many elements are there in the world?
The first full-scale hydrogen bomb explosion in
the Pacific in late 1952 produced two new
chemical elements, atomic scientists disclosed
today. The researchers recommend that the new
elements be named after Dr. Albert Einstein and
Dr. Enrico Fermi, who played major roles in the
birth of the atomic age (New York Times, August
1955)
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Composition of Earths crust (8 Major Elements)
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Periodic Table of the Elements
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PERIODIC TABLE OF ELEMENTS

• Ordered by increasing atomic weight and atomic
  number (Z number of protons in the nucleus of
  one atom).
• Atomic weight (grams/mol) is given below the
  element symbol.

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Avogadros Number

• Avogadros number was determined experimentally
  in the 20th century, but was named in honour of
  19th century Italian chemist LORENZO ROMANO
  AMEDEO CARLO AVOGADRO

• The 2002 CODATA recommended value for Avogadro's
  number is

6.0221415 x 1023 mol-1
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Avogadros Number

• Avogadros number (N ) gives the number of atoms
  in 1 mole of an element

• Magnitude of N If the Earth was covered by N
  peas, the peas would be piled to a height of 0.5
  km!

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How many atoms are in my body?

• Suppose that I am made entirely of carbon
• Suppose that I weigh 72.0 kg
• Number of moles (mol) of carbon
• Number of carbon atoms 6.00 103 mol 6.022
  1023 atoms/mol 3.61 1027 atoms

1 mol X mol
X 7.2x104/12.01 6.00x103 mol

12.01 g 7.20104 g
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