Lab 2

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The Atom
Lab 2
2
The Bohr Model
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Whats Inside an Atom?

• An atom is made up of a team of three players
  protons, neutrons, and electrons
• They each have a charge, mass, and a location
• Protons Neutrons collectively called nucleons

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What is the structure of an atom?

• Nucleus center of the atom
• Home of Protons and Neutrons
• Proton
• Has a positive () charge
• Has a relative mass of 1
• Determines the atomic number
• Found inside the nucleus

P
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What is the structure of an atom?

• Neutron
• Has no charge (0)
• Has a relative mass of 1
• Determines the isotope
• Isotopes are two of the same element with
  different masses
• Found inside the nucleus

N
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What is the structure of an atom?

• Electron
• Has a negative (-) charge
• Has a relative mass of 0 (zero)
• Determines the ion
• Found outside the nucleus

e
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Electrons circle around the nucleus of an atom.
Protons are a main part of the nucleus of an atom.
Neutrons also hang out in the nucleus of an atom.
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Electrons have a negative charge. ?
Protons have a positive charge.
Neutrons have no charge. 0
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Electrons are little and have a mass of almost
zero.
Protons are big and have a mass of one.
Neutrons are also big and have a mass of one.
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The Bohr Model
The Bohr Model
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How are P, N, e- related?

• protons atomic number Z
• electrons protons in a neutral atom
• protons neutrons mass number A

• Ex The atomic number of Hydrogen (H) is 1, so
  all hydrogen atoms have 1 proton.
• Ex All Oxygen atoms (O) have 8 protons, so the
  atomic number of Oxygen is 8.
• Remember all atoms are electrically neutral.
• Therefore the number of Protons equal the number
  of Electrons.
• Meaning the number of negatively charged
  particles must equal the number of postively
  charged particles.

• Ex Helium (He) has 2 protons and 2 neutrons its
  mass number is 4.
• Ex Carbon (C) has 6 protons and 6 neutrons its
  mass number is12.

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A
Structure of the Nucleus

• protons neutrons mass number A

• X

Z
N

• neutrons

• protons atomic number Z

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A
Structure of the Nucleus
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• Al

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Structure of the Nucleus

• The ratio of the number of neutrons to the number
  of protons N/Z is an approimate index of the
  stability of a nuclide.
• N/Z 1 in the stable nuclei with low atomic no.
• Ex, C

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Nomenclature

• Isotopes
• Nuclides of the same atomic number. O O
  O
• Isotones
• Nuclides having the same number of neutrons but
  different atomic number
• Fe Co Cu
• Isobars
• Nuclides with the same no. of nucleons that is
  the same mass no. but different no. of protons
• Cu Zn
• Isomers
• Nuclides having the same number of protons and
  neutrons but differing in energy states and
  spins. 99Tc 99mTc

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60
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Units of Radioactivity

• 1 curie (Ci) 3.7 X 10 10 dps
• 2.22 X 10 12 dpm
• 1 millicurie (µCi) 3.7 X 10 7 dps
• 2.22 X 10 9 dpm
• 1 microcurie (µCi) 3.7 X 10 4 dps
• 2.22 X 10 6 dpm

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Units of Radioactivity

• 1 Becquerel (Bq) 1 dps 2.7 X 10 -11 Curie
• 1 kilobecquerel (Bq) 2.7 X 10 -8 Curie
• 1 Ci 3.7 X 10 10 Becquerel (Bq)

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Decay Equations

• -dN/dtYN
• Y Lambda decay constant.
• Defined as the probability of disintegration per
  unit time for the radioactive atom
• -dN/dt A disintegration rate
• N is the no. of radioactive atoms
• At Aoe-yt
• AyN
• Y0693/t1/2
• t1/2 the time required to reduce the intial
  activity of a radionuclide to one half

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Problems

1. At 1100 A.M., the 99mTc readioactivity was
   measured as 9 mCi on a certain day. What was the
   activity at 800 A.M. and 400 P.M. on he same
   day (t1/2 of 99mTc 6hr)

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Thank You

• Instead of giving yourself reasons why you cant
  , give yourself reasons why you can