Bonding Flashcards
(16 cards)
Define the metallic bond
The attraction between positive metal ions and delocalised electrons
Define ionic bonding
The electrostatic attraction between oppositely charged ions.
Boron
Does not form ions
A covalent bond is
A shared pair of electrons
Non-Octet molecules do not have
A full outer shell
A coordinate bond is
A covalent bond in which both electrons of the shared pair come from the same atom. They can be shown using an arrow.
-The atom that donates the e- had a lone pair.
-The atom that accepts the e- does not have a full outer shell so it is electron deficient.
How to work out # of e- pairs in a molecule
(Group # of central atom + #of bonded atoms - charge) / 2
Then the # of lp can be calculated using the formula:
#e- pairs - #Bonded atoms
Shapes of molecules with no lone pairs
2 bp & 0 lp = Linear - 180 degrees
3 bp & 0 lp = Trigonal planar/Trigonal bonds - 120 degrees
4 bp & 0 lp = Tetrahedral - 109.5 degrees
5 bp & 0 lp = Trigonal bypyramid - 120 and 90 degrees
6 bp & 0 lp = Octahedral - 90 degrees
Shapes of molecules with lone pairs
2 bp & 1 lp = V-shaped - 117.5 degrees
3 bp & 1 lp = Pyramidal - 107 degrees
2 bp & 2 lp = V-shaped - 104.5
3 bp & 2 lp = Trigonal planar - 120 degrees
4 bp & 2 lp = square planar - 90 degrees
Electronegativity is
The power of an atom to attract the pair of electrons in a covalent bond.
-it increases across a period and decreases down a group.
Distinguish between polar and non-polar bonds
Non-polar covalent bond - no or very small difference in electronegativity.
Polar covalent bond - a significant difference in electronegativity.
-A bond is polar when N, O, F, Cl, Br and Iodine atoms bond to a different atom.
Polar molecules
A molecule is non-polar if its symmetrical as the bond dipoles cancel.
A molecule is polar if it’s asymmetrical as the bond dipoles do not cancel - molecules with lone pairs are often but not always asymmetric.
Intermolecular forces: VDW
Van der Waals’ forces arise from the movement of electrons, creating a temporary dipole in 1 molecule. This temporary dipole induces a dipole in a neighbouring molecule and these dipoles attract. VDW forces strength depends on the number of electrons in a molecule.
Intermolecular forces: Permanent dipole-dipole forces
These occur between polar molecules and occur in addition to VDW forces.
The S+ end of 1 molecule attracted to the S- end of a neighbouring molecule (one has to be below the other).
Intermolecular forces: hydrogen bonds
Occurs between molecules which contain a hydrogen atom bonded to either F, O or N.
Hydrogen bonds are formed between a S+ Hydrogen atom in one molecule and a lone pair of electrons on a O, N or F in a neighbouring molecule.
When drawing hydrogen bonds you must show
-2 molecules
-All lone lairs
-Partial charges
-The correct alignment of atoms
