how does the concept of ionic bonding account for each of its following properties?
i) low electrical conductivity as solids and high conductivity in solution or when molten
ii) relatively high melting and boiling points
iii) brittleness
iv) solubility in polar solvents
i) low electrical conductivity as solids and high conductivity in solution or when molten
ii) relatively high melting and boiling points
iii) brittleness
iv) solubility in polar solvents
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For (i):
In ionic bonding, it is a bond between cations and anions in which electrons are transfered to create the compound. However in solid form, the electrons are held too tightly to move (held in tight lattice structures), thus unable to conduct electricity but in molten or aqueous form, electrons are able to move freely.
(ii):
Ionic compounds have high MP and BP because of the strong electrostatic charge between the anion and cation (as they are negatively and positively charged ions respectively). It takes a great deal of energy from heat to overcome these forces, thus the high MP and BP.
(iii):
Think of ionic bonding as a lattice structure, formed with the ions, forming a cube. When stress is added to the compound, the lattice layer will shift, like shearing the top of the cube. This is the brittleness. Not really explained properly so just go to this website: http://www.ausetute.com.au/ionicbond.html
(iv):
Have you heard of 'like dissolves like'? This basically means that a polar solvent will dissolve in another polar substance or non polar in a non polar substance. Since ionic bonding is between a positive and negative ion, it is a polar substance. Thus in another polar substances it will happily dissolve due to the intermolecular bonds. In the ionic substnce, one side is more positive and the other more negative. So in a polar substance, the same thing is happening in the molecule, one side is positive and other more negative. When these subtances are mixed together, they will dissolve as the positive side of the polar substance will bond with the negative side of the ionic compound and vice versa.
In ionic bonding, it is a bond between cations and anions in which electrons are transfered to create the compound. However in solid form, the electrons are held too tightly to move (held in tight lattice structures), thus unable to conduct electricity but in molten or aqueous form, electrons are able to move freely.
(ii):
Ionic compounds have high MP and BP because of the strong electrostatic charge between the anion and cation (as they are negatively and positively charged ions respectively). It takes a great deal of energy from heat to overcome these forces, thus the high MP and BP.
(iii):
Think of ionic bonding as a lattice structure, formed with the ions, forming a cube. When stress is added to the compound, the lattice layer will shift, like shearing the top of the cube. This is the brittleness. Not really explained properly so just go to this website: http://www.ausetute.com.au/ionicbond.html
(iv):
Have you heard of 'like dissolves like'? This basically means that a polar solvent will dissolve in another polar substance or non polar in a non polar substance. Since ionic bonding is between a positive and negative ion, it is a polar substance. Thus in another polar substances it will happily dissolve due to the intermolecular bonds. In the ionic substnce, one side is more positive and the other more negative. So in a polar substance, the same thing is happening in the molecule, one side is positive and other more negative. When these subtances are mixed together, they will dissolve as the positive side of the polar substance will bond with the negative side of the ionic compound and vice versa.