Ozone at lowest concentrations in the Antartic spring
Special weather conditions
Exceptionally low temperatures
Below -80\(^\circ\)C
Form stratospheric clouds
Tiny solid particles
Mainly ice
Some rich in nitric acid
Provide surface for chemical reactions
Vortex of circulating air forms in Antartic winter
Isolates air at centre
Forms giant reaction vessel
Chlorine reservoir molecules adsorbed onto surface of molecules in stratospheric clouds \[ClONO_2+HCl\Rightarrow Cl_2+HNO_3\]
\(HNO_3\) remains dissolved
Chlorine released into core of vortex
In spring, vortex breaks up
Chlorine undergoes homolytic fission to form chlorine atoms
The effect is more variable and less drastic over the artic, but it extends over more densely populated areas.
Strongest type of intermolecular bonding - a special case of permanent-permanent dipole bonding. For hydrogen bonding to occur, three features required/;
A large dipole
Between hydrogen atom and highly electronegative atom
Small hydrogen atom
Lone pair of electrons on the negative atom
In hydrogen fluoride, HF, the molecule is strongly polar. The positive hydrogens line up with the negative lone pairs on another fluorine. As the hydrogen is small, the two atoms can get close, and attract very strongly.
Hydrogen fluoride has the highest MBP because the electronegativity of halogens decreases down the group.
Water molecules form twice as many hydrogen bonds, as the oxygen has two lone pairs, and there are twice as many hydrogen atoms as oxygen atoms.
This property is unique to water. Despite hydrogen fluoride having three lone pairs, there are only as many hydrogen atoms as fluorine atoms, meaning only one third of the lone pairs can be used.
More energy is required to break hydrogen bonds than instantaneous-induced dipole bonds. Liquids that hydrogen bond have high visocity - water is an exception, as it is not viscous - as flowing requires the constant breaking and forming of intermolecular bonds.
Substances that hydrogen bond are often soluble in water, as the water will hydrogen bond too, helping the dissolving process.
When water freezes, it forms ice crystals. The open structure, with four groups around each oxygen atom, maximises hydrogen bonding, and can be used to explain why ice floats.