Chemistry for life: Elements of life

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  • Created by: Lois
  • Created on: 04-04-13 18:26
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  • This includes 3 types of sub-atomic particles: protons, neutrons and electrons
    • Protons: 1 relative atomic mass, +1 charge, located in the nucleus of the atom
      • Neutrons: 1 relative atomic mass, 0 charge, located in the nucleus of the atom
        • Electrons: very small (0.00055) relative atomic mass, -1 charge, located around the nucleus of the atom
  • Elements of life
    • 2.2 - Nuclear reactions
      • Some isotopes are unstable and so their nuclei break down spontaneously, and so are described as radioactive - radioisotopes
        • As these nuclei break down they emit rays & particles called emissions - alpha, beta and gamma
          • All types of emissions are capable of knocking off electrons from the atoms they collide with - ionises them
      • Nuclear fusion is the fusing of 2 atomic nuclei, to form a single heavier nucleus and releases energy
        • High temperatures, high pressure, high kinetic energy are needed to overcome the repulsion between the two nuclei
      • The term for half the nuclei to decay is called half-life
        • The half-life is fixed so temperature & pressure do not effect it
    • 2.1 - A simple model of the atom
      • Many chemical and nuclear processes can be explained by a simple model of atomic structure
        • This includes 3 types of sub-atomic particles: protons, neutrons and electrons
          • Protons: 1 relative atomic mass, +1 charge, located in the nucleus of the atom
            • Neutrons: 1 relative atomic mass, 0 charge, located in the nucleus of the atom
              • Electrons: very small (0.00055) relative atomic mass, -1 charge, located around the nucleus of the atom
      • The atomic number (Z) is the no. of protons and is also numerically equal to the charge on the nucleus
        • The mass number (A) is the number of protons + neutrons
      • Atoms of the same element which have different mass numbers are called isotopes, this is because of different numbers of neutrons
      • The relative atomic mass is an average of the masses of the isotopes, taking into account their abundances
    • 6.1 - Light & electrons
      • Speed of light = wavelength times freq
        • Energy of a photon = freq of light, on wave model,  multiplied by constant h (Plancks constant 6.63 times 10-34J Hz-1
      • Emission spectrum - coloured lines on a black background
        • Absorption spectrum - black lines on a coloured background
      • Ionisation is when an atom loses an electron
    • 2.3 - Electronic structure: shells
      • 1st shell - 2 electrons, 2nd shell - 8 electrons, 3rd shell - 18 electrons, 4th shell - 32 electrons
    • 3.1 - Chemical bonding
      • Bond polarity: when two atoms of different sizes are bonded, the core of the smaller atom will be closer to the shared electrons and will exert a stronger pull on them
        • different atoms attract electrons unequally, one atoms gets a slight negative charge as it has a greater share of the bonding electrons;the other becomes slightly positively charged (polar bonds)
      • Electronegativity: the electron pulling power - a measure of each atom's attraction for bonding electrons
        • excluding the noble gases the more electronegative elements are at the top of the group & right-hand side of the periodic table
          • the highest electronegativities correspond to reactibe non-metals with small atoms, we can use differences in electronegativity values to predict how polar a particular covalent bond will be
    • 3.2 - The shapes of molecules
      • 2 groups of electrons: linear with 180*
      • 3 groups of electrons: planar triangular with 120*
      • Water is 109* due to lone pairs
      • 4 groups of electrons: tetrahedral 90* & or 90*
      • 5  groups: trigonal bipyramidal with 120* or 90*
      • 6 groups of electrons: octahedral  with 90*
    • 1.1 - Amount of substance
      • The relative atomic mass of an element is the mass of its atom relative to carbon-12
      • The relative formula mass is the mass of its formula unit relative to C-12
      • A mole of substance is the amount of substance which contains as many formula units as there are atom in 12g of C-12
      • The molar mass is the mass of substance which contains 1 mole
      • Avogadro's constant: one mole of any substance contains 6.02 times 10 *23 formula units
      • The empirical formula tell you the simplest ratio of the numbers of different types of atom in the substance
      • The molecular formula tells you the actual numbers of different types of atom
    • 1.2 - Balancing equations
      • Decide reactants & products
        • write formulae for the substances involved
          • balance so there is the same numbers of each atom on each side
            • include state symbols
    • 11.2 - The s block: groups 1 & 2
      • More metallic as you go down the group - soft weak metals with low melting points (compounds more important)
        • All very reactive - never found in uncombined state
          • all react with water to form hydroxides & hydrogen, hydroxides solubility increases down the group, carbonates solubility decreases down the group
    • 6.5 - Mass spectrometry
      • Measures the atomic or molecular mass of particles
        • Vacuum chamber of: ionisation area, acceleration area (so same kinetic energy), drift region and ion-detector
          • the most abundant ion gives the strongest detector signal which is the base peak
            • the smallest ions are detected first and KE= 0.5(mv*2)
    • 11.1 - Periodicity
      • The modern periodic table is arranged by  atomic number
        • The occurrence of periodic patterns is called periodicity
          • there can be periodicity in chemical formulae, ionisation enthalpies and chemical properties
  • 1st shell - 2 electrons, 2nd shell - 8 electrons, 3rd shell - 18 electrons, 4th shell - 32 electrons
  • The relative formula mass is the mass of its formula unit relative to C-12
  • The occurrence of periodic patterns is called periodicity
    • there can be periodicity in chemical formulae, ionisation enthalpies and chemical properties

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