9 Big picture about redox

Redox reaction is about the transfer of electron(s) from an atom (or ion) to another atom (or ion) that has more electron affinity, results in a change in charge

 

Example from Periodicity chapter

Machine generated alternative text:F most reactive attracts electrons easily least reactive has great difficulty attracting electrons

1. Cl2 (aq) +       2 Br- (aq)      -->     Br2 (aq) +          2 Cl- (aq)

This is a redox reaction

2. Cl2 (aq) +       2 F- (aq)        -->     NO REACTION

  • Comparing the reactivity (based on ability to attract electron) of the two elements will tell you whether the reaction happens spontaneously or not
  • If the reaction doesn't happen such as this example, you can force the electron transfer using external sources of energy. Ie. Electrical current produced by a battery

 

HL: Lewis acids accept and Lewis bases donate lone pair electrons, so is Lewis acid base reaction a redox reaction?

  • NO. In Lewis acid base reaction, the lone pair electrons are usually shared as a covalent bond. There is NO CHANGE in the overall charge of the molecule/ atom so it is not redox reaction.
  • Redox reaction usually involves ionic compounds.
  • Acid + metal --> hydrogen gas + salt is redox where electron is transferred from metal to H+. Thus only metal that is more reactive than H+ can react with acid.
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