atomic structure book 1.2

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  • Atomic Structure
    • History
      • 1897-JJ. Thompson discovered the electron. he also showed that the atom can be split into smaller parts.
        • PLUM PUDDING MODEL: regarded the atom as a positively charged sphere in which the negative where distributed all over it(i.e currents in a pudding)
      • 1911- Creigor and Marsden preformed a series of experiments which produced a new model of the atom. a thin gold foil was bombarded with alpha particles from a radium source. particles leaving the atom where detected by a flash of light.
      • Rutherford suggested that the positive charge of an atom and the mass was concentrated in a tiny region called the nucleus. he proposed that it was negative atoms orbiting one tiny positive atom.
      • in the following years improvement were made to his model. Neils Bhor applied quantum theory to this and managed to knock the positive atoms out and found protons. which where 1800 times heavier than electrons.
      • 1932- james chadwick discovered particles the same mass as protons and named them neutrons
    • Structure of an Atom
      • with one exception all atoms are made up of 3 particles: electrons neutrons and protons
      • they all contain a necleus apart from on exception which consists of protons and neutrons the remaining particles (electrons) orbit the necleus
    • Relative Charge and Relative Mass
      • ELECTR0N: relative charge is -1    relative mass is almost 0
      • PROTON: relative charge is +1 relative mass is 1
      • NEUTRON: relative charge is 0 relative mass is 1
    • Atomic Number and Mass Number
      • an atomic number is the number of protons in the necleus of an atom
      • the mass number is the total umber of protons and neutrons in a neculus
    • Subatomic particles and Charges
      • protons and electrons are electrically charged yet atoms themselves have no overall charge. this is because there charges are equal and cancel out eachother
      • atomic number=number of protons
        • number of protons=number of electrons
        • number of neutrons=mass number - atomic number
    • Electronic Structure and Configuration
      • the first lowest energy leval can hold up to 2 electrons
      • the second can hold up to 8
      • the third can initially hold up to 8
      • the electrons enter the lower energy levals first and then are filled in order
    • Ions
      • in certain situations the atoms may gain or loose electrons.
      • if an atom loses on or more electrons it becomes a positive ion
        • if an atom gains one or more it becomes negative
        • the number of electrons the atom loses or gains determines the size of the overall charge
      • positive ions are called cations and negative ions are called anions ( CATions are PUSSYtive


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