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To make one mole of CaCl<sub>3</sub>, one can estimate that 1341 kJ of heat would be needed. This makes this compound completely non-viable. Why is so much heat needed to make CaCl3? It is because the third ionisation energy (the energy needed to remove the third electron) is extremely high (4940 kJ mol<sup>-1</sup>) because the electron is being removed from the 3-level rather than the 4-level. Because it is much closer to the nucleus than the first two electrons removed, it is going to be held much more strongly.
 
To make one mole of CaCl<sub>3</sub>, one can estimate that 1341 kJ of heat would be needed. This makes this compound completely non-viable. Why is so much heat needed to make CaCl3? It is because the third ionisation energy (the energy needed to remove the third electron) is extremely high (4940 kJ mol<sup>-1</sup>) because the electron is being removed from the 3-level rather than the 4-level. Because it is much closer to the nucleus than the first two electrons removed, it is going to be held much more strongly.
 
   
 
   
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A similar sort of argument applies to the negative ion. For example, [[oxygen]] forms an O<sup>2-</sup> ion rather than an O<sup>-</sup> ion or an O3- ion, because compounds containing the O<sup>2-</sup> ion turn out to be the most energetically stable.
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A similar sort of argument applies to the negative ion. For example, [[oxygen]] forms an O<sup>2-</sup> ion rather than an O<sup>-</sup> ion or an O<sup>3-</sup> ion, because compounds containing the O<sup>2-</sup> ion turn out to be the most energetically stable.
    
[[Category:Chemistry]]
 
[[Category:Chemistry]]
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