Bonding:
Covalent: valence electrons are "shared" in pairs between atoms. e.g. Cl has 7 electrons in its outer shell. It prefers a full outer-shell, hence two Cl bonds together and shares a pair of electrons (one each): [Cl]*x[Cl], one pair shared.
Ionic: instead of "sharing", it becomes a give-take. e.g. Na has 1 valence electron, whereas Cl has 7. Na wants to lose one, Cl wants to gain one. Hence, Na loses an electron and becaomse Na+ [remembering electrons are negatively charged], and Cl- gains this electron and becomes Cl-
Because of the charges, these atoms are now called "ions", and they arrange themselves into regular lattices, as crystals.
Metallic: instead of give-take as in the case of ionic bonding, a group of metals rid themselves with their valence electrons [all becoming positively charged cations]. the cations, instead of repelling themselves apart, are held together by the electrons which are now "delocalised", that they no longer belong to any particular atom, but to the metal lattice, filling gaps between the metal cations, and holding it together.
Intermolecular bonding:
[some atoms *want* electrons more than others, this depends on how far away the shells are from the nucleus, how many valence electrons there are, and how many protons there are. when this *want* is strong, an element is said to be "electronegative"]
Dipole-Dipole - covalent bonds between non-metallic atoms of significant difference in electronegativity. because of this difference in electronegativity, the electrons are likely to be closer to the more electronegative element more, hence the bond is polar, where one side is slightly positive, and the other is slightly negative. depending on the shape of the molecule, if if is not symmetrical [in 3D], then this polarity allows the positive ends to attract to negative ends.
Hydrogen bonding - strong dipole-dipole bonding, typically the intermolecular attraction of H-O, H-F, and H-N bonds
Dispersion forces - probability dictates that sometimes electrons may be on one side of an atom/bond, making an instantaneous dipole that has a slightly-slight charge. hence, the more electrons there are, the more possibility this attraction can occur, i.e. bigger molecules [densely packed as well] will have higher dispersion forces despite them not having dipole-dipole intermolecular bonds.
[very brief and not rigourously explained]
[this stuff, you should have covered in detail in class.]
Home
Help
Search
Login
