Subatomic Particles Atomic Structure

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Subatomic ParticlesAtomic Structure

• Is it really the smallest thing out there?

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Atoms

• The smallest particle of an element that retains
  the properties of that element
• These are mostly chemical properties, not
  physical properties

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Subatomic Particles

• Particles of matter that make up atoms
• Smaller than atoms themselves
• Behave differently than whole atoms

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Electrons

• Negatively charged particles found outside the
  nucleus in an area known as the electron cloud
• Discovered by JJ Thomson during the Cathode Ray
  Tube experiment

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Protons

• Positively charged particles found in the nucleus
  of the atom
• Discovered by Ernest Rutherford ( associates)
  during the Gold Foil Experiment

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Neutrons

• Particles with no charge found in the nucleus of
  the atom
• Discovered by James Chadwick

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Comparison of Subatomic Particles
Particle Symbol Charge Relative Mass
Electron e- -1
Proton p 1 1
Neutron n0 0 1
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Atomic Nucleus

• The central core of the atom
• Composed of protons neutrons
• it has a positive charge
• Held together by the strong nuclear force
• One of the four fundamental forces in the
  universe
• It contains almost all of the mass of the atom
  (very dense)

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Atomic Nucleus

• It is a very small percentage of the volume of
  the atom
• Marble in a football stadium
• As the nucleus gets larger, it becomes harder to
  create and more unstable
• Why?

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Atomic Number

• The number of protons an atom contains
• Found on the periodic table
• The number of protons identifies the atom
• Atoms of different elements will have different
  number of protons and different atomic numbers

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Number of Electrons

• Whole atoms are electronically neutral
• They must have the same number of protons
  (positive charge) and electrons (negative charge)
• The atomic number is also the number of electrons
  an atom contains

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Mass Number

• An (overwhelmingly) large majority of the mass of
  an atom is located in the nucleus
• Protons Neutrons are in the nucleus
• Mass Number is the sum of the number of protons
  and the number of neutrons

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Isotopes

• Atoms that have the same number of protons, but
  different number of neutrons
• They are the same element with a different mass
• Same atomic number
• Different mass numbers

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Identifying Isotopes

• Element Name Mass Number
• Oxygen-16
• 8 protons/8 neutrons
• Chlorine-35
• 17 protons/18 neutrons
• Uranium-238
• 92 protons/146 neutrons

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Identifying Isotopes

• X elemental symbol
• Z Atomic Number
• A Mass Number