> For the complete documentation index, see [llms.txt](https://knowmayus.gitbook.io/chemistry/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowmayus.gitbook.io/chemistry/unit-1/oxidation-states-3.1.6.md).

# Oxidation States (3.1.6 )

Bonding is often not ionic or covalent, but rather a continuum with unequal sharing of electrons.

**Oxidation States/Oxidation numbers** are used to represent the charge of an atom if it was composed of ions.  It also shows the number of electrons being transferred or shared when bonding.

**E.x.**  Water ($$H\_2O$$)--> "Covalent" .  If it was Ionic,  Oxygen ( $$O^{-2}$$ ) would gain two electrons and hydrogen ( $$H^{+1}$$)would each lose one.  Thus,

Hydrogen has oxidation state of +1.  And Oxygen is assigned an Oxidation state of -2.

**Rules to deduce oxidation states of atoms**

1. Oxidation state of any free element is zero.
2. The sum of the oxidation States of all atoms in a neutral compound is zero.
3. Sum of Oxidation States of all atoms in a polyatomic ion is equal to the charge of the ion.
4. Oxidation state of fluorine is -1 in all compounds.
5. The oxidation state of group 1 --> + 1 / Oxidation state of group 2 --> +2  **ALWAYS**
6. **Oxygen** always have oxidation state of +2, **except** in  $$OF\_2$$where flourine is more electronegative ( Oxygen has state of +2 here ), and in peroxides  $$H\_2O\_2$$( Oxygen has state of -1 here ), the oxidation state is always -1.
7. Hydrogen's Oxidation state is: 
   1. +1 when combined w/ more electronegative elements ( most non-metals )
   2. -1 when combined w/ less electronegative elements ( metals ). When this happens, this compound is called a Hydride Ion.

**Acid rain & Ocean Acidfication:**

* Water generally has pH of $$7.0$$ neither acidic or basic, but w/ Carbon Dioxide, it forms a weak acid.

$$CO\_2(g) + H\_2O(l) \rightarrow HCO\_3 (aq )$$

More Carbon Dioxide means more Carbonic Acid into the ocean, affecting the health of coral reef.

The pH of rainwater is **5.6.** But for other Oxides, like  Nitrogen Oxide ($$NO$$ ) & Sulfur  Dioxide ( $$SO\_2$$ ) the case is different:  Their rain can have a pH less than 5.6 which is called **acid rain**.

These oxides can come from volcanos, decomposing vegetation, and industrial processes.

<figure><img src="https://1345459981-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FU8XLVR7CYYLRlgazrP2A%2Fuploads%2FwyGDSmsd5pbwc0x1zDcX%2Fimage.png?alt=media&amp;token=27f431d2-61a6-4685-b53b-753a2e1feade" alt=""><figcaption></figcaption></figure>

The nitrous & sulfurous acid though just oxides back into the nitric acid & Sulfuric Acid.

<figure><img src="https://1345459981-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FU8XLVR7CYYLRlgazrP2A%2Fuploads%2FT3ub1pw0pB5YRwIxrxWa%2Fimage.png?alt=media&amp;token=7545c1fb-d10d-44f5-930d-29ffdda14d83" alt=""><figcaption></figcaption></figure>