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Unformatted text preview: 1 CH 2. Atoms, ions and the periodic table Daltons Atomic Theory Structure of the Atom Ions Atomic Mass Math toolbox 1.1 (pp. 36- 3 7) The Periodic Table Daltons ( modern ) Atomic Theory Daltons Atomic Theory has 4 postulates: 1. All matter is composed of exceedingly small, indivisible particles called atoms . 2. All atoms of a given element are identical both in mass and in chemical properties . However, atoms of different elements have different masses and different chemical properties. 3. Atoms cannot be created or destroyed in chemical reactions. 4. Atoms combine in simple, fixed, whole-number ratios to form compounds. This was proven wrong later - see isotopes Structure of the Atom Nuclear Atom Atom is divisible and made of subatomic particles Subatomic particles include: Electrons: outside nucleus; negatively charged Particles in the nucleus Protons: positively charged Neutrons: uncharged 2 The Discovery of Electrons (1897) Figure 2.5 J.J. Thomson proved The existence of electron Negative charge Pudding model ( incorrect ) Charge/mass ratio Charge by oil drop experiment (Millikan, see p.58) Rutherford: The Nuclear Atom Subatomic Particles ( Table 2.1, p.60 ) Proton ( p ): Q = +1.6022 x 10-19 C (expressed as +1 ) m = 1.6726 x 10-24 g ( hydrogen atom ) Neutron ( n ): no charge m = 1.6749 x 10-24 g Electron ( e ): Q = - 1.6022 x 10-19 C (expressed as - 1 ) m = 9.1094 x 10= 9....
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