Cation just is a positive ion. Anion is just a negative ion. And so this one right over here is now positive. Sodium is now positive. Chloride is a negative ion. And so they're going to be attracted to each other, and they're going to form this ionic bond.
So this right over here is an ionic bond. Now let's think about something that's not ionic, where the electrons are not being fully nabbed from one atom to another, but they're being shared. And one of the most famous examples of that is water. So we know water is H2O. Each water molecule is one oxygen bonded to two hydrogens. And these two bonds are covalent bonds.
In each of these bonds, you have a pair of electrons that are being shared by both the hydrogen and the oxygen. But we also know that this isn't a completely equal sharing of the electrons. We look on the periodic table here, oxygen is far more electronegative than hydrogen is. And so because of that, the electrons in these two bonds are going to spend more time around oxygen than they are going to spend around the hydrogens.
And we've seen this before. This would give the oxygen end of the water molecule a partially negative charge. That's the lowercase Greek letter delta. We use that for the notation of partially negative. And on the hydrogen ends of the molecule, we're going to have a partially positive charge. Now, this is the reality. But as we'll see later on in future videos, it's sometimes inconvenient to have this partial messiness. And so what I'm going to do right now is introduce you to what is fundamentally just an intellectual tool.
It's just a convention that chemists have invented that allow us to get our heads around a lot of reactions and allow us to think about how is a reaction likely to occur. And that intellectual tool is the idea of oxidation states. What the oxidation state is, even if you're in a situation where you have covalent bond, you say, well, look, I understand. Those are partial charges.
These are covalent bonds. The electrons are being shared. But I don't like this partial stuff. I want to just assume hypothetically, what if these were ionic bonds? And you say, well, if these had to be ionic bonds, then the oxygen would nab the electrons from these pairs. And so the oxygen would have a fully negative charge, a negative 2 charge.
And the hydrogens would have a fully positive charge each. And so, if we were to write down the oxidation states for the atoms in the water molecule-- let's write that down, so H2O-- we would say that oxygen has an oxidation state of negative 2, and each hydrogen atom has an oxidation state of plus 1.
And notice, the whole molecule is neutral, and these things cancel out with each other. Positive 1, positive 1, that gets you to positive 2. Then you have negative 2. They cancel out. Now, the one thing, I keep saying this is negative 2, but I wrote the negative after it.
If I wanted to write positive 1 as an oxidation state, I would actually write it as 1 positive, although you can assume that if someone just writes the positive.
And this is just the convention, to write the sign after the number when we are writing actually ionic charges or oxidation states, because an oxidation state is nothing but a hypothetical ionic charge. If you really had to-- if you were forced to assume these aren't covalent bonds, but these are ionic bonds. Once again, I want to stress. The hydrogen ions are gaining electrons and bonding together to form dihydrogen gas.
The hydrogen ions each gained an electron to form the neutrally charged hydrogen gas. The hydrogen ions are said to be reduced and the reaction is a reduction reaction. Since both processes are going on at the same time, the initial reaction is called an oxidation-reduction reaction. You could just memorize oxidation: lose electrons-reduction: gain electrons, but there are other ways.
There are two mnemonics to remember which reaction is oxidation and which reaction is reductions. Oxidation and reduction reactions are common when working with acids and bases and other electrochemical processes.
Use these two mnemonics to help keep in mind which process is the oxidation and which is the reduction reaction. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads.
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List of Partners vendors. Since an oxidation reaction releases electrons, there should be an electron accepting species. Therefore, the oxidation reaction is a half reaction of a major reaction. The oxidation of a chemical species is given as the change of its oxidation states. However, this definition is no longer accurate since there are many more oxidation reactions that occur in the absence of oxygen.
The following example shows the oxidation and reduction reactions in a redox reaction. Figure Oxidation of Mg by the addition of Oxygen to Mg. Two electrons are released from Mg, and one oxygen atom obtains two electrons. There is another historical definition for oxidation involving Hydrogen. Figure The oxidation of alcohol group into Carboxylic acid group.
An oxidation always increases the oxidation state of a chemical species due to the loss of electrons. This loss of electrons causes the charge of an atom or molecule to be changed. A molecule or an atom that has no electrical charge neutral can be oxidized. The oxidation always increases the oxidation state. Therefore, the new oxidation state of the atom would be a positive value.
Figure The oxidation of O -2 to O2 0. A neutral atom is composed of protons positively charged in the nucleus and electrons negatively charged around the nucleus.
The positive charge of the nucleus is balanced by the negative charges of electrons. Then the atom gets a positive charge.
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