can you mention the concept of oxidation state without its simple definition i-e it is the apparent charge +ve or -ve.....😪 I found these in wikipedia but didn't understand."Conceptually, the oxidation state, which may be positive, negative or zero, is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic, with no covalent component. This is never exactly true for real bonds.". what does it mean? please clear with example if possible.
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$\begingroup$ The gist is that no bond is 100% ionic or covalent. Obviously some are mostly ionic or covalent, but not 100% of either extreme. $\endgroup$– MaxWCommented Jan 17, 2019 at 6:57
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1$\begingroup$ In the "oxidation state" theory, we assume that the "oxidation state" is always an integer. What the sentence in Wikipedia means is just that the real charge is usually not an integer. $\endgroup$– SteffXCommented Jan 17, 2019 at 16:28
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Oxidation state is a formal number ascribed to atoms, to tell if it has more or less electrons than in its natural state.
For single atoms it is fairly straightforward, as electrons can only be removed or added in discrete units. Therefore, an atom or ion has an oxidation state that equals it electric charge.
But electrons are not small particles, orbiting the molecule. In many ways an electron is better described as a cloud of negative charge hovering around the molecule and chemical bonds.
When different atoms are connected in a molecule, this cloud is not evenly distributed between the atoms. Example: In Carbonmonoxide (CO) the Oxygen attracts most of the electron-cloud. But not all, if so the molecule would part into ions.
In reality, the oxidation state of the atoms in CO should be calculated with decimals instead of whole numbers, but for practical reasons we ascribe the whole of an electron in a bond to one of the atoms.
In Carbonmonoxide the atoms are bonded by a double-bond (4 electrons) and if all of these “belongs” to oxygen it will have two more than the basic atom and thus the oxidation state is -2.
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Oxidation states are whole numbers assigned to individual atoms that are part of molecules or ions. They serve to describe oxidation and reduction reactions. An increase in oxidation state is associated with oxidation (loss of electrons) while a decrease is associated with reduction (gain of electrons).
There are multiple sets of rules how to assign oxidation states to atoms (see for example section on oxidation reduction reactions here or what to do for organic molecules here). Sometimes, there is disagreement how exactly to assign oxidation states (it is a conceptual number, you can't measure it), but in all cases, the sum of the oxidation states of all atoms in a molecule or ion or complex has to equal the net charge of that species. This means you have to (artificially) assign each electron to an individual atom based on specific rules or based on electronegativity scales.
To give examples of oxidation states, the carbon in methane has an oxidation state of minus four, while the carbon in carbon dioxide has an oxidation state of plus four. Hydrogen is mostly assigned an oxidation state of plus one, and oxygen mostly an oxidation state of minus two.
When methane is burned (i.e. reacts with elemental oxygen), it is oxidized to form carbon dioxide in an oxidation process. At the same time, the elemental oxygen is reduced to form water and parts of the carbon dioxide. Together, this is called a redox reaction, and there is a transfer of electrons (electrons are available from the oxidation half reaction, and are required for the reduction half reaction).
