Draw Lewis structures for these chlorofluorocarbons (CFCs), which are partly responsible for the depletion of ozone in the stratosphere: \(\mathrm{CFCl}_{3}, \mathrm{CF}_{2} \mathrm{Cl}_{2}\), \(\mathrm{CHF}_{2} \mathrm{Cl}, \mathrm{CF}_{3} \mathrm{CHF}_{2}\).

Chlorofluorocarbons, commonly known as CFCs, are man-made chemical compounds that once held vital roles in various industries, notably as refrigerants, solvents, and propellants in aerosol sprays. These compounds are composed of chlorine, fluorine, and carbon. The environmental concern around CFCs arose when it was discovered that they contribute significantly to the depletion of the ozone layer in the stratosphere.

The ozone layer is crucial because it protects the Earth from the harmful ultraviolet (UV) rays of the sun. When CFCs reach the upper atmosphere, they are broken down by UV light, releasing chlorine atoms. These chlorine atoms are highly reactive and can destroy thousands of ozone molecules before they are removed from the stratosphere. Consequently, CFCs have been largely phased out, replaced by more environmentally friendly alternatives, following international agreements like the Montreal Protocol.

Valence electrons are the outermost electrons of an atom and play a fundamental role in chemical reactions and bonding. They are responsible for the formation of chemical bonds as they can be lost, gained, or shared to create a full outer shell, making the atom more stable.

For example, in CFCs, atoms like chlorine and fluorine have seven valence electrons and are one electron short of a full octet, which makes them highly reactive and capable of forming strong bonds with other atoms. Carbon, with its four valence electrons, is versatile in forming covalent bonds. In constructing Lewis structures of molecules, determining the number of valence electrons is crucial as it guides the bond formation and distribution of remaining electrons in the molecule.

The octet rule is a chemical rule of thumb that states atoms tend to combine in such a way that they each have eight electrons in their valence shells, giving them the same electronic configuration as a noble gas. The rule is applicable to the main group elements, especially carbon, nitrogen, oxygen, and the halogens, as these elements will form bonds to complete their octet.

In creating Lewis structures for CFCs, the octet rule helps us determine how atoms will share electrons through bonding. If an atom has fewer than eight electrons, it will seek to share or gain electrons to reach a stable state. This rule, however, is not universal; it has exceptions, particularly with elements that can have an expanded octet, like phosphorus and sulfur, and with hydrogen, which abides by the 'duet rule' as it is stable with only two electrons.