CI 2.1 &CI 2.3

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  • Created by: Leena
  • Created on: 14-08-15 09:55
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  • ATOMS
    • All matter is composed of tiny particles called atoms.
    • 3 Main Components
      • Proton
        • Equal to the number of electrons in a neutral atom.
        • Number of protons - Identifies the element
        • Relative Mass = 1
        • Relative Charge = +1
      • Electron
        • Equal to the number of protons in a neutral atom,
        • Relative Mass = 1/1836
        • Relative Charge = -1
        • Arranged in energy levels or shells.
          • Each shell has a number - quantum number n
            • The higher the value of n, the further the shell is from the nucleus and the higher the energy associated with the shell.
            • Each shell can hold a fixed number of electrons.
              • 1st shell - n=1 - 2 electrons.
              • 2nd shell - n=2 - 8 electrons
              • 3rd shell - n=3 - 18 electrons
              • 4th shell - n=4 - 32 electrons
              • Examples of rule breakers
                • Potassium, 19K - 2.8.8.1
                • Calcium, 20Ca - 2.8.8.2
                • Scandium, 21Sc - 2.8.9.2
                • Titanium, 22Ti - 2.8.10.2
                • Electron configurations not as expected - resulting from overlap of energy levels within shells 3 &4.
                  • Electrons 19 & 20 have more stability if placed in shell 4 rather than shell 3.
      • Neutron
        • Relative Mass = 1
        • Relative Charge = 0
    • Ions
      • Atoms which have gained or lost one or more electrons resulting in an overall +ve or -ve charge.
      • Anion (-ve ion)
        • Has gained electrons/ more electrons than protons.
      • Cation (+ve ion)
        • Has lost electrons/ fewer electrons than protons
    • Isotopes
      • Atoms of the same element with the same number of protons but different number of neutrons/mass number
      • Chemically identical but have different physical properties - e.g mass, density, mp/bp.
    • Relative Atomic Mass, Ar
      • Average mass of an atom relative to the mass of 12C=12 - from the weighted average of the atomic masses of the naturally occurring isotopes of element.
      • Calculation
        • -Multiply isotopic mass by % abundance for each isotope  - Add up these totals    - Divide by total abundances.
    • Mass Number, A
      • Number of protons + neutrons in the nucleus.
    • Atomic Number, Z
      • Number of protons in the nucleus

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