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OCR B (Salters) AS level Chemistry
UNIT 2 ­ F332

Elements from the sea
Halogens and Halides (group 7 chemistry)

Halogen is the elemental molecule, eg/ Cl, Br
Halide is in a compound, eg/ KBr, KCl

Fluorine Chlorine Bromine Iodine
Appearance Pale yellow Green gas Dark red Shiny black
at…

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Element Oxidation number
Fluorine -1
Oxygen -2 (unless with Fluorine)
Chlorine -1 (unless with Fluorine or Oxygen, then +1)
Hydrogen +1


Working out oxidations states is really just simple maths.



Ion Oxidation state of Name of ion
chlorine
ClO +1 Chlorate (I)
ClO +3 Chlorate (III)
ClO +5 Chlorate (V)…

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Needs to be covalently bonded.
One element has to be more electronegative then the other.
Has to have a delta negative end and delta positive end according to
the shape of the molecule.




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Nucleophillic substitution
`A nucleophile is a species which is strongly attracted to a region of positive
charge in another molecule, and can donate an electron pair'

SN2 mechanism

Example;




The Nu ion represents the attacking nucleophile
Curley arrows show the movement of electron pairs
The nucleophile is attracted to the…

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The first ionisation energy is the energy required to remove the most loosely
held electron from one mole of gaseous atoms to produce 1 mole of gaseous
ions each with a charge of 1+.
This is more easily seen in symbol terms.


It is the energy needed to carry out…

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Last calculations
Number of moles = Volume (dm³) x Molarity (mol dm³)
% uncertainty = (total error range) / (volume) x 100




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Comments

Valentina

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really helpful, thanks


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