Unit #1Unit #2Unit #3Unit #4Unit #5Unit #6Unit #7Unit #8Unit #9Unit #10
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spacerof the Atom

spacerAtomic Number - Number of Protons
spacerNumber of Electrons
spacerMass Number - Number of Neutrons
spacer3.2 Isotopes
spacer3.3 Arrangement
spacerof Electrons

spacerThe Bohr Model
spacerBohr Diagram
spacerThe Lewis Electron-dot Symbol
spacerThe Quantum Mechanical Model of the Atom
spacerElectrons in the sublevels

spacer3.4 Electron

spacerFilling Order of the Sublevels

spacerElectron Configuration Notations
spacerElectron Configuration for Atoms of the First 20 Elements
spacerElectron Configuration and the Periodic Table
spacer3.5 Atomic Mass
spacerCalculation of Atomic Mass
spacerCalculate the Atomic Mass of Carbon

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3.2 - Isotopes

Let's take a look at the carbon atom in detail. There are two types of carbon atoms that are found in nature. We call them carbon-12 and carbon-13. Using symbols, carbon-12 and carbon-13 can be written as follows:

The symbol describes carbon-12 as follows:
  • "C" indicates the atom is Carbon
  • Z = 6 indicates carbon-12 has 6 protons
  • A = 12 indicates that the mass number is 12
  • number of neutron = 12 - 6 = 6 neutrons
The symbol describes carbon-13 as follows:
  • "C" indicates the atom is Carbon
  • Z = 6 indicates carbon-13 has 6 protons
  • A = 13 indicates that the mass number is 13
  • number of neutron = 13 - 6 = 7 neutrons

Points to note:

  • carbon-12 and carbon-13 are atoms that have the same atomic number but different mass numbers. Carbon-12 and carbon-13 are called isotopes.
  • carbon-12 has 6 neutrons and carbon-13 has 7 neutrons.
  • Isotopes of the same element (i.e. such as carbon-12 and carbon-13) have similar chemical properties.

Section 4.5
Isotopes ..p85




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