Chemistry

Chemistry

1. Structure of the Atom

   • Atoms have protons and neutrons in a central nucleus, with electrons in shells around the nucleus
   • Isotopes
     • The atomic number of an element is the number of protons in the nucleus
     • The mass number is the total number of protons and neutrons in the nucleus
     • Isotopes are atoms of the same element with different numbers of neutrons. This means some relative atomic masses are not whole numbers
       • An example of a Isotope is Sodium
   • A proton have a relative mass of 1 and a relative charge of +1
   • A neutron has a relative mass of 1 and a relative charge of 0
   • A electron has a relative mass of 0.1840 and a relative charge of -1

2. The modern periodic table

   • The elements in the modern peordic table are arranged in the order of their atomic numbers
   • Mendeleev
     • The peordic table as we know it was mde by Mendeleev, who arranged all the elements known at the time intoa table
     • Mendeleev put the elements in order of their relative atomic mass.
       • He left gaps where he thought there were other elements, and predicted their properties.
       • He swapped the places of some elements so that elements with similar properties lined up.
       • When these elements were discovered, Mendeleev's predictions fitted the properties very well.
       • He checked the properties of the elements and their compounds.

3. Electron Shells

   • Electronic configuration: The electronic fill the shells that are closest to the nucleus first. The diagram

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