- Created by: zopetre_
- Created on: 23-04-17 11:39
What are the three types of bonding?
Ionic, covalent and metallic
What is the basic cause of bonding?
The positively charged nuclei and negatively charged electrons are arranged in such a way that the electrostatic attractions outweigh repulsion.
Describe covalent bonding
Covalent bonding is between non-metals.
Each atom gives one electron to form a bond pair, in which the electron spins are opposed.
Describe coordinate/dative bonding
Coordinate/dative bonding is the same as covalent bonding, however, both electrons which form the bond pair are given from the same atom.
Describe ionic bonding
Ionic bonding occurs between positive and negative ions.
One atom gives one or more electrons to the other, and therefore the resulting cation and anion attract eachother electrically.
What happens if atoms get too close together?
The nuclei and their inner electrons will repel those of the other atom, and the bond will have a certain length.
Describe metallic bonding
It's between metal atoms.
It consists of a lattice of positive ions which are held together by a 'sea' of delocalised electrons, which are given up by each atom.
Why is a bond polar?
It becomes polar when one atom takes up a slightly negative charge, and the other becomes slightly positive.
What is electronegativity?
A measure of the electron-attracting power of an atom.
What is intermolecular bonding?
The weak bonding that holds molecules together, and governs the physical properties of the substance.
What is intramolecular bonding?
The strong bonding between atoms in the molecule, governing its chemistry.
What are the two types of intermolecular bonding?
Induced dipole - when a dipole induces an opposite dipole in a nearby molecule. The electrons are always in constant motion and they're always formed and broken.
Permanent dipole-dipole - additional electorstatic forces of attraction between polar molecules.
Describe hydrogen bonding
A special intermolecular bonding force. It only occurs between molecules that contain hydrogen atoms bonding to very electronegative elements having lone pairs (fluorine, oxygen and nitrogen).
It's much stronger than van der Waals forces, 300kJ compared to 3kJ.
It's stronger because the hydrogen atom is sandwiched between two electronegative elements.
What is the effect of H bonding on boiling tempera
Melting/boiling temperature increase with the strength of intermolecular forces.
They can dissolve other molecules such as the lower alcohol with which they can hydrogen bond. non-polar organic molecules such as hydrocarbons that cannot hydrogen bond with water are insoluble in it, and prefer to interact with one another through van der Waals forces.
What is the repulsion sequence?
Lone pair - lone pair > lone pair - bond pair > bond pair - bond pair
What does VSEPR stand for and what does it let us
Valence Shell Electron Pair Repulsion theory lets us predict the shape of simple molecules in which bonded atoms are arranged around a central atom.
How do you work out the shape/bond angle?
Find out the number of electron pairs.
2 pairs = linear and 180 degrees. e.g. BeCl2
3 pairs = trigonal planar and 120 degrees. e.g. BF3
4 pairs = tetrahedral and 109.5 degrees. e.g. CH4
5 pairs = trigonal bipyramid and 90/120 degrees. e.g. PCl5
6 pairs - octrahedral and 90 degrees. e.g. SF6
What shapes should you know and be able to explain
BF3, CH4, NH4+ and SF6