Notes on Chemical Bonding :: Chemistry

Chemical notes on bonding Ionic bonding - This occurs between metals and non metals - Fe2+/3+, Cu+/2+, Zn2+, No3- - Metals loose electrons, non metals gain electrons. - Ionic compounds conduct electricity when dissolved, but not when solid, they also have high m & b points due to strong giant 3d lattice. They are also soluble in water as they have a charge - Metal atoms always form positive charged electrons while non metals from negatively charged electrons Metallic Bonding - They conduct electricity due to a sea of delocalised electrons - They have a lattice of positive atoms. - Transition metals contribute both S and D electrons in the sea of electrons - The attraction is between the ions and mobile valence electrons and not between the layers, this means they can bend over each other - The large the number of valence electrons and the smaller the atoms and the stronger the metallic bonding Covalent bonding - Between non metals with high electron values - Can have single, double, or triple bonds Bond strength C – C: single bond, longest type of bond (154) however is the easiest to break (346) C=C: double bond, second longest bond (134) and second hardest to break (598) C=C: triple bond, smallest bond (121) however is the hardest to break (837) Predicting the type of bonding (1) From electronegativity Electronegativity is the strength of an element/atom to pull electrons towards itself. Metals have a very low electronegativity as they lose electrons in ionic bonding, however non metals have a higher electronegativity as they gain electrons in ionic bonding. (2) From position in the periodic table Metal + non metal = ionic bonding Non metal + non metal = covalent bonding Simple molecular structure Molecular covalent bonds have low m & b points because of weak intermolecular forces called Van Der Waals forces. (more on this later) Giant covalent structures Diamond and graphite both have these structures but they are very different. They both have a giant lattice with strong covalent bonds, in the case of Diamond it is 3d and very hard to break in any way, however with graphite it is only 2d so can be broken if cracked in a certain way. These structures have very high melting and boiling points. Buckminsterfullerere A family of ball shaped C-molecules in which there are around 60 atoms which are found in ball shapes. Uses are being investigated in nano-thecnology. These substances are soluble in non-polar solvents Polar bonds The larger the difference in electronegativity the greater the strength of the polar bond. Now the hard stuff