Topic 1

Topic 1

1. Atoms and the Periodic Table.

   • The Modern Periodic Table.
     • Atomic number instead of atomic mass.
   • Mendeleev's Table.
     • 1869
     • He worked out the atomic mass of the missing element and predict their properties.
     • There were gaps in his table due to undiscovered elememts.
     • Order of relative atomic mass.
     • Arranged so groups of elements with similar properties fell into vertical columns in his table.
   • Atomic Structure
     • Nucleus- Protons and Neutrons
     • Nucleus is always positively charged and is very small compared to the size of the atom.
     • The atom has a neutral overall charge as they have the same number of protons and electron.
     • Protons and neutrons have the same mass.
     • Electron have a tiny mass.
     • The atomic number is the number of protons in an atom.
     • The mass number is the total number of protons and neutrons in an atom.
     • Isotopes are the same element with a different number of neutrons.

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