If oxygen in the air is O2 (since an oxygen atom has 6 electrons in the outer shell, it makes 2 double covalent bonds with another oxygen so that they’re both stable), why do oxygen molecules react with metals to form an oxide layer if O2 is stable? Its stable, so why react with anything?

182 views

If oxygen in the air is O2 (since an oxygen atom has 6 electrons in the outer shell, it makes 2 double covalent bonds with another oxygen so that they’re both stable), why do oxygen molecules react with metals to form an oxide layer if O2 is stable? Its stable, so why react with anything?

In: Chemistry

[removed]

Stability is relative. Nature tends towards the lowest energy state, O2 has a lower energy than lone oxygen atoms floating around. So if you have gaseous oxygen it is stable as O2. However it isn’t in its lowest energy state, if there is some copper in the system then the oxygen can react with it and release energy. The copper oxide had a lower energy than the lone copper and oxygen and so is a more stable state.

Not all oxygen in the air exists as O2. The majority is O2; however, oxygen can also exist as ozone (O3), which can split into an O2 and a free oxygen radical (O·).

“Ozone is formed when heat and sunlight cause chemical reactions between oxides of nitrogen (NOX ) and Volatile Organic Compounds (VOC), which are also known as Hydrocarbons.” So basically nitrogen oxides & fuel sources react in sunlight to form ozone.

This means there are always free oxygen radicals in the atmosphere – these are responsible for most of the reactivity with oxygen.

Because it doesn’t actually make these two bonds. O2 has an unstable second bond that will also exist as two unpaired electrons. This configuration is called a radical. Many molecules exist like this or can be turned into one by something like UV light or bumping into a radical. There are also molecules that are good at absorbing radical elections and stabilizing that lone electron. This makes O2 a kinda reactive gas. Not as much as chlorine but still way more than CO2. Stability isn’t a binary but more a sliding scale based on the type of molecule in question.

O2 will react over time with metals forming a far more stable structure than just O2. This lowers the energy of the molecules net net so is a favorable reaction.

As you probably know atomic oxygen has six outer electrons. When two oxygen atoms get together they share some elections so each atom “has the use of” eight (Google covalent bond). But copper atoms are willing to donate electrons “permanently” to oxygen atoms so both “own” complete outer shells which both find “more satisfying” (Google Ionic bond).

Of course “If you can’t measure it you don’t understand it” and the measurement of this “satisfaction” is the energy level referred to by other posters (lower energy = more satisfied).