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Chemistry (Periodic Law (Electronegativity (Period Trends (Tends to…

- - - - Tends to increase across a period because valence shells are closer to being filled.
    - - Tends to decrease down a group or stay the same.
- - - - forms when valence electrons are transferred from one atom to another. In ionic compounds the ions are arranged in a crystal lattice. Strong forces hold the ions together. Electronegativity difference greater than or equal to 1.7.
    - - Nonpolar Covalent Bond
        
        electrons are shared equally because atoms have the same electronegativities . Electronegativity difference less than or equal to 0.3
      - Polar Covalent Bond
        
        electrons are shared unequally, creating partially charged ends or poles. Electronegativity difference between 1.7 and 0.3.
    - - electrons are delocalized( creates sea of electrons)
- - - - A unit of length would be measured using the SI unit "meter."
      - A unit of time would be measured using the SI unit "seconds."
      - A unit of mass would be measured using the SI unit "kilogram."
- - - - Cathode Rays and Electrons
        
        Cathode rays were deflected by a magnetic field in the same manner as a wire carrying electric current, which was known to have a negative charge.
        
        The rays were deflected away from a negatively charged object
        
        A paddle wheel placed on rails between the electrodes rolled along the rails from the cathode toward the anode
        
        An object placed between the cathode and the opposite end of the tube cast a shadow on the glass
    - - John Dalton proposed an explanation for the law of multiple proportions, law of conservation of mass, and the law of definite proportions.
        
        5 postulates of Dalton's theory:
        
        Today we know that atoms are divisible into even smaller particles and a given element can have atoms with different masses.
        
        All matter is composed of extremely small particles.
        
        Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
        
        Atoms cannot be subdivided, created, or destroyed.
        
        Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
        
        In chemical reactions, atoms are combined, separated, rearranged.
    - - Gold Foil Experiment
        
        The Gold Foil Experiment is when scientist discovered that every atom contains a nucleus where all of the atom's protons and most of its mass is located.
        
        Rutherford concluded that rebounded alpha particles experienced some powerful force within the atom, and that the source of the force must occupy a very small amount of space.
    - - Rutherford's student
      - Bohr explained what happens inside of an atom and developed a picture of atomic structure.