Changes

===Characteristics of Ionic Compounds===

===Characteristics of Ionic Compounds===

#Crystalline solids at room temperature  

#Crystalline solids at room temperature  

#Have higher melting points and boiling points compared to co-valent compounds  

#Have higher melting points and boiling points compared to covalent compounds  

#Conduct electrical current in molten or dissolved state  

#Conduct electrical current in molten or dissolved state  

#Are extremely polar bonds  

#Are extremely polar bonds  

That means that elements forming positive ions will tend to give away as many electrons as possible.

That means that elements forming positive ions will tend to give away as many electrons as possible.

Energy is needed to remove electrons from atoms. This is called ionisation energy. The more electrons removed, the greater the total ionisation energy becomes. Eventually the total ionisation energy needed becomes so great that the energy released when the attractions are set up between positive and negative ions isn't large enough to cover it.

Energy is needed to remove electrons from atoms. This is called ionization energy. The more electrons removed, the greater the total ionization energy becomes. Eventually the total ionisation energy needed becomes so great that the energy released when the attractions are set up between positive and negative ions isn't large enough to cover it.

The element forms the ion which makes the compound most stable - the one in which most energy is released over-all.

The element forms the ion which makes the compound most stable - the one in which most energy is released over-all.

However, making CaCl2 (containing Ca²⁺ ions) releases more heat, 795 kJ. That extra amount of heat evolved makes the compound more stable, which is why CaCl₂ rather than CaCl is formed.

However, making CaCl2 (containing Ca²⁺ ions) releases more heat, 795 kJ. That extra amount of heat evolved makes the compound more stable, which is why CaCl₂ rather than CaCl is formed.

To make one mole of CaCl₃, 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^-1) 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 CaCl₃, 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 ionization energy (the energy needed to remove the third electron) is extremely high (4940 kJ mol^-1) 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.

   

   

A similar sort of argument applies to the negative ion. For example, [[oxygen]] forms an O^2- ion rather than an O^- ion or an O^3- ion, because compounds containing the O^2- ion turn out to be the most energetically stable.

A similar sort of argument applies to the negative ion. For example, [[oxygen]] forms an O^2- ion rather than an O^- ion or an O^3- ion, because compounds containing the O^2- ion turn out to be the most energetically stable.

[[Category:Chemistry]]

[[Category:Chemistry]]