Elements of life

Elements of life

1. Atom

   • Electron
     • 0.005 mass
     • -1 Charge
   • Proton
     • 1 mass
     • +1 Charge
   • Neutron
     • 1 mass
     • 0 Charge
   • Isotope
     • Same number of protons and electrons different number of neutrons.
   • Nuclear fusion
     • Two light atomic nuclei fuse together to form a single heavier nucleus.

2. Moles

   • Mole= Mass/Mr
   • Mole=Concentration X liquid
   • Mole= Volume of Gas/ 24
   • Avargardos constant 6.02 X10^23

3. Spectroscopy

   • Absorption Spectra
     • Shows black lines on a coloured background, the lines correspond to light that has been absorbed by a sample.
   • Emission Spectra
     • Black with coloured lines, the lines are produced when electrons falls from a higher energy level to a lower energy level.
   • Theory of light
     • Light is part of the electromagnetic spectrum, therefor is a wave. Speed of light = Wavelength X Frequency
     • Light is particles, streams of tiny packets of energy called photons. Energy of Photon = Planck Constant X Frequency
   • Bohr's theory
     • The main points
       • Electron in hydrogen atom exsists only in certain definite energy levels or electron shells
       • Photon of light is emitted or absorbed when the electron changes from one energy level to another
       • Energy of the photon is equal to the difference between the two energy levels
       • Since E=HV it follows that the frequency of the emitted or absorbed light is related to energy levels
     • Lyman series- lines represent the energy levels of the electron the further away from the nucleus the higher the energy level

4. Electronic subshell

   • Sub shell
     • S=2 electrons
     • P=6 electrons
     • D=10 electrons
     • F=14 electrons
   • S has a sphere orbital
   • P has a dumpbell orbital
   • Half filled sub shell reduces repulsion
   • Chromium and copper have halved filled subshells
   • Calcium= 1S2 2S2 2P6 3S2 SP6 4S2

5. Periodicity

   • Period 3
     • Increase across period 3 the melting point and boiling point increase then falls dramatically at silicon and phosphorus due to weak bonds between the partcles
   • Group 1
     • Form +1 ions
     • Become more reactive with water as you go down
   • Group 2
     • Form +2 ions
   • Group 7
     • Form -1 ions
     • Halogens become more reactive as you go up
   • Group 6
     • Form -2 ions

6. Bonding

   • Covalent
     • Between two non-metals
     • Electrons shared
     • Dative bond formed when both bonding electrons come from one atom
     • VSEPR Electrons will position itself so least repulsion
     • Covalent network
       • Strong covalent bonds
       • Melting/Boiling point are very high
       • Very hard
       • Do not conduct electricity apart from Graphite
       • Insoluble
   • Bond angles
     • Linear=2 bonding regions=180
     • V shaped=2 bonding and 2 non bonding=104.5
     • Tetrahedral=4 bonding=109.5
     • Trigonal planar=3 bonding=120
     • Pyramidal=3 bonding and one non bonding=107
     • Bi-Pyramidal=5 bonding=120+90
     • Octahedral=6 bonding=90
   • Ionic
     • Between metal and non metals
     • Properties
       • High melting/boiling point
       • Soluble in water
       • Conduct electricity if molten or in a solution electrons free to move
       • Hard but brittle
       • Bonded by strong ionic bonds
     • Ionic Salt
       • Acid + Alkali --> Satl + Water
       • Acid + Base --> Salt + water
       • Acid + Carbonate --> Salt + Water + Carbon dioxide
       • Acid + Metal --> Salt + Hydrogen
     • Spectator ion- Ion present but do not react
   • Metallic
     • Strong metallic bonds
     • Melting/boiling point generally high
     • Hard but malleable
     • Conduct when solid or liquid
     • Insoluble

7. Precipitation reactions

   • Cu + 2OH --> Cu(OH)2 Blue
   • Fe2+ + 2OH --> Fe(OH)2 Dirty green
   • Fe3+ + 2OH --> Fe(OH)3 Orange/brown
   • Pb + 2I --> Pbl2 Bright yellow
   • Ag + Cl --> AgCl White
   • Ag + Br --> AgBr Cream
   • Ag + I --> AgI Pale yellow
   • Ba + SO2 --> BaSO4 White

8. Covalent molecular

   • Simple molecular
     • Weak intermolecular bonds
     • Low mellting/boiling point
     • Soft
     • Do not conduct
     • Insoluble
   • Macromolecular
     • Weak intermolecular bonds
     • Moderate boiling/melting point
     • Do not conduct electricity
     • Usually insoluble

9. Ionisation enthalphy

   • First ionisation enthalphy is the energy required to remove one mole of electrons from one mole of atoms in their gaseous state
   • Second ionisation enthalphy the energy required to remove a second mole of electrons from one mole of gaseous cations
   • As you go down the groups the ionisation enthalphy decreases because the distance from the nucleus increases
   • As you move across a period ionisation enthalphy increases
   • Peaks at group 0 due to full outer shell
   • Troughs at group 1 as it is easier to ionise
   • S-block metals become more metallic down a group
   • Charge density- As a element become bigger charge density decreases
   • Group 2 carbonates become more stable down the group because group 2 oxides react with acid because they are basic.
   • Thermal decomposition can be explained in terms of charge density- the smaller the cation the higher the charge density.
   • Cations with higher charge density can distort or polarise the negative charge cloud around the carbonte making it easier to break

10. Acids and bases

    • Acid- A compound that dissolves in water to produce hydrogen ions and are proton donors
    • Base- A compound that reacts with an acid is a proton acceptor to produce water and a salt
    • Alkali- A base that dissolves in water to produce hydroxide ions

11. Flame test

    • Li Bright red
    • Na Yellow
    • K Lilac
    • Ca brick red
    • Ba apple green
    • Cu blue green