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IB Bonding
Question | Answer |
---|---|
Ionic bond | electrons transferred from one atom to another to form ions with complete outer shells of electrons. High melting pt. |
Polyatomic ions | charge is delocalized over whole ion |
Covalent bonding | sharing of one or more pairs of electrons so that each atom in the molecule achieves a stable outer shell of electrons |
Single covalent bond | sharing of one pair of electrons. sigma bond. longest and weakest covalent bond. |
Double covalent bond | sharing of two paris of electrons. sigma and pi bond. moderate covalent bond length and strength |
triple covalent bond | sharing of three pairs of electrons. sigma and two pi bonds. shortest and strongest covalent bond. |
co-ordinate covalent bond | electrons in the shared pair originate from the same atom |
Polar bonds | when one atom is more electronegative than another resulting in slightly + and - atoms |
VSPER theory (valence shell electron pair repulsion) | pairs of electrons arrange themselves around the central atom so that they are as far apart from each other as possible. greater repulsion between non-bonded pairs than between bonded pairs. |
linear | 180 |
trigonal planar | 120 |
tetrahedral | 109.5 |
trigonal bipyramidal | 90, 120 |
octahedral | 90 |
how to work out the actual shape | calculate the number of pairs of electrons around central atom, work out how many bonding pairs/non-bonding pairs |
molecular polarity | depends on relative electronegativities of the atoms and on the shape |
Van der Waals forces | electrons unevenly spread at any one moment that produces temporary instantaneous dipoles that induce another dipole in a neighboring particle. Increase with increasing mass. |
intermolecular forces | forces of attraction between molecules |
dipole-dipole forces | polar molecules are attracted to each other by electrostatic forces. stronger than Van der Waals |
hydrogen bonding | occurs when H is bonded directly to a small, highly electronegative element like F, O, N, resulting in a very strong dipole-dipole force. |
metallic bonding | valence electrons in metals become detached from the atoms so that metals consist of a close packed lattice of positive ions in a sea of delocalized electrons. |
Melting and Boiling Points | indicates strength of intermolecular forces. BP is when the attractive forces are completely broken; MP is when the crystal solid structure is broken and some intermolecular forces remain |
solubility | "like dissolves like". Polar dissolves in polar, non-polar in non-polar. The longer an organic molecule, the less soluble it is in water. |
Conductivity | substance must possess electrons or ions that are free to move. Metals and molten ionic salts conduct electricity. |
sigma bond | formed when two atomic orbitals on different atoms overlap "head-on". |
pi bond | formed when two p orbitals overlap "sideways-on". Made of two regions of electron density |
sp3 hybridization | 4 sp orbitals, 4 single bonds. tetrahedryl shape |
sp2 hybridization | 3 sp orbitals, 1 p orbital. 3 single bonds; 2 single bonds, 1 double bond. trigonal planar shape |
sp hybridization | 2 sp orbitals, 2 p orbitals. 2 single bonds; 2 double bonds; 1 single 1 triple bond. linear shape |
resonance structure | when it is possible to write more than one correct structure with regard to bonds. |
delocalization of electrons | can occur whenever alternate double and single bonds occur between carbon atoms. |
diamond | sp3 hybridized. |
graphite | sp2 hybridized. delocalized electrons-conduct electricity. |