grade 11 chemistry Learners in today's video we will be looking at Redux reactions this will be an introduction and a basic overview of Redux reactions it's very important to watch this video and then to check out the links in the description box below for links to the playlist for other videos that go more in depth on each of the subtopics that I will mention in this video Let's Jump Right In but remember to subscribe to Miss Martin's Math and Science if you haven't yet so I can help you get the best possible marks for physic sciences and math let's Jump Right In I want to start off by reminding you about ionic bonding now remember when we have ionic bonding occurring it involves a transfer of electrons we have a metal a non-metal you learned about this in grade 10 and this year and what essentially happens is that my metal over here atom number one has an electron over here what it does is it gives away it loses an electron that electron is transferred to atom number two which gains that electron okay once this happens we form a positively charged object or particle a negatively charged object or particle and they attract that's ionic bonding now Redux reactions involves the transfer of electrons and we can contrast this with acid base reactions which you may or may not have done this year already but acid base reactions in involve the transfer of protons or hydrogen ions H+ ions protons Redux reactions involves the transfer of electrons which are as you know negatively charged particles a large number of Redux reactions take place in aquous or aquous Solutions but they're not limited to these types of solutions they don't have to occur in them and a lot of students when I say Redux reactions what are you thinking a lot of my students say oxygen a lot of them do involve oxygen and that is how we get rust like you see on this picture but not all of them involve oxygen that's why when you are asked to define a redo reaction you need to Define it in this way please a reaction where electrons are transferred and the word redox reactions actually tells us a lot of information as you can see I highlighted this piece of the word in red the red part of the word and this stands for reduction and the ox part of the word stands for oxidation now these two words are super important if I say that reduction has occurred or something has been reduced what that means is that thing has gained electrons it has gained or accepted electrons if I say oxidation has occurred or something has been oxidized what it means is that that substance has lost electrons and one way that you you can remember it that I always use there are other ways but oil rig oil means oxidation is loss oxidation is loss remember loss of what loss of electrons rig means reduction is gain gain of what gain of electrons so that's how I remember what oxidation is and what reduction is in terms of electron transfer if you quickly take a look at this example which we will revisit in a few minutes you can see we've got sodium and chlorine now remember these are the Lis dot diagrams that you draw using the veence electrons or the electrons in the outermost orbital if you've forgotten how to do that go check out the videos in my playlist on lou. diagrams and chemical bonding but sodium has one veence electron and chlorine has seven veence electrons now what this means is that in order to reach a complete or full outer orbital or energy level sodium has to lose that one electron then it reaches full outer energy level and chlorine needs to gain one electron to reach octet structure eight electrons then it has a full outer energy level so what happens is basically sodium loses that electron it gives it away and remember we said that oxidation is loss of electrons so what that means is sodium is oxidized it losts an electron and chlorine gains that electron and remember reduction is gain of electrons so chlorine is reduced and why does this process happen the two elements want to bond with each other and reach a full outer energy level structure so Redux reactions oxidation reduction Redux they take place simultaneously which means at the same time one substance or chemical is reduced another is oxidized and as I said sometimes oxygen is involved but not all now here is a very important summary of definitions for you that you need to know so first one we went through second one and third one we went through sort of so oxidation is the loss of electrons reduction is the gain of electrons so if you are asked to Define oxidation and reduction in terms of electron transfer the first little piece of these definitions that's how you'll do it however you can also Define oxidation and reduction in terms of something called an oxidation number we will get into more detail about oxidation numbers in another video but oxidation numbers that's closely related to the veency or the charges of a substance if we see an increase in oxidation number it means that the substance has been oxidized oxidation has been taken place if we see a decrease in oxidation numbers it means that the substance has been reduced reduction has taken place very very important I will show you in a second again about oxidation numbers more or less but fullon video in the playlist then we have oxidizing agent and reducing agent now this is how I always teach it to my students if you are oxidized you are the reducing agent if you are reduced you are the oxidizing agent so think opposites go together so if you read this definition for oxidizing agent that is the substance that is reduced if you are the reducing agent that is the substance that is oxidized so these are the terms that need to go together in your brain If oxidation takes place you say that the substance is oxidized it is also called the reducing agent if reduction has taken place the substance is reduced it is also called the oxidizing agent if we take a look at this example that you see on the green we've got potassium plus chlorine and that forms potassium chloride very similar to my example earlier with sodium potassium if you can see I don't know if it's clear here but potassium has one valence electron chlorine has seven potassium will give away that electron so potassium loses the electron as you can see and I will go over this later but the oxidation number of potassium was zero and in this molecule it's it's + one so what happened to the number it went from 0 to 1 it increased the oxidation number increased which means oxidation took place it means potassium is oxidized it means that potassium lost electrons now think about it like this if you lose electrons remember electrons are negative if you lose something that is negative you become more positive which is why the oxidation number goes from 0 to Plus one you're losing the negative stuff you're losing one electron so you become more positive you go to plus one and remember if you are oxidized you are also called the reducing agent so pottassium K is the reducing agent if we look at this over here let's look at what reduction is happening over here what has been reduced we can see that chlorine had seven veence electrons over here it gained an electron from potassium the electron went this way when because chlorine gains electrons we say that it is reduced so CL is reduced and remember if you are reduced you are the oxidizing agent and reduction is the gain of electrons if you gain negative things electrons you become more negative so your oxidation number goes from 0 to -1 it all fits together it all makes sense now we will go over oxidation numbers in more Det detail in another video but we can use oxidation numbers to help us determine what substance is oxidized and what is reduced so I will teach you the rules in a separate video look at the links down below but I'm telling you now the oxidation number for sodium is zero the oxidation number for chlorine is zero when they stand alone it's a rule when they're in a compound sodium has an oxidation number of plus one because it's in the first group again this is a rule chlorine is a hallogen it has an oxidation number of zero I mean netive 1 okay again it's a rule we will do this in the separate video together plus one minus one it must give me zero because NAC sodium chloride is a neutral compound again sodium goes from 0 to plus1 it's an increase in oxidation number therefore sodium is oxidized chlorine goes from 0 to1 it's a decrease in oxidation number so chlorine is reduced now once we know what is oxidized and what is reduced we can write something called a half reaction so remember we've said the following sodium is oxidized it's the reducing agents oxidation is loss of electrons so when we have half reactions we have these are half reactions so with an arrow it's like a little this like it looks like this like a reaction these are reactants Arrow products half reactions we get an oxidation half reaction and a reduction half reaction now the oxidation half reaction shows what happens when oxidation takes place so oxidation half reaction shows the loss of electrons so what I mean is the following we start off with sodium na then what happens it loses electrons after it loses electron so we use the arrow it was sodium then it becomes we use an arrow after it loses an electron remember sodium has one veence electron so it'll lose one electron if you lose something that is negative you become positive it forms the na+ ion the sodium ion with a charge of plus one it's also in group one so it makes sense that its valency is + one now how did it become na A+ it lost an electron so we have to show it lost the electron when you see and I said this to my grade 11s it helps it make it bit easier for them when you see electrons on the right hand side of the arrow it means oxidation it means that the half reaction is representing oxidation and the reason why is because it is losing electrons it's giving that electron away it's no longer part of the sodium anymore it's giv it away then we have the reduction half reaction so what's happening here is CL is reduced which means it gains electrons the CL gains that electron that's why we say CL Plus plus the electron gives me cl L minus if you gain a negative you become negative you get a charge of minus you gain one electron you get a charge of one minus or minus one and generally moving forward in future videos when we do Redux reactions we're going to learn how to use table 4 a or 4 B which looks like this so we'll go into this table in more detail in future videos like I said but essentially this lists a whole bunch of half reactions now they are written it's very difficult to see on this version of the table but they're written with double arrows and that's because the reaction can be read this way or this way so if I pick one of them from the table for example the Magnesium half reaction I can either write the half reaction this way which means it'll look like this or I can write the half reaction the other way which means it'll look like this please note that when I write half reaction so a reduction half reaction or oxidation half reaction this represents one half reaction here this represents the other half reaction at the bottom over here take note how I always use a single Arrow this is very important all the way up to mat trick I know it's written with double arrows on the table but you need to use a single Arrow so think about it carefully pause the screen if you must which of these two number one or number two which of these represents a oxidation half reaction and which one represents a reduction half reaction think about it I hope that you said that this one at the bottom represents the oxidation half reaction because oxidation is loss oil oxidation is loss of electrons electrons are on the right hand side and this one represents the reduction half reaction because reduction is gain of electrons the mg2+ ion is being reduced the mg2+ ion is gaining these two electrons to form magnesium so how you would write this actually if I had to ask you what substance is oxidized you would say that magnesium is oxidized it's also called the reducing agents and that is what's taking place in this reaction over here and if you look at this reaction over here you would say that mg2+ is reduced not just mg mg2+ is reduced why because mg2+ the magnesium ion is the thing that is actually accepting the electrons and remember reduction is gain of electrons so that means that mg2+ is the oxidizing agent I hope that the terminology is starting to become a little bit more familiar to you don't stress out about this table this table is always given to you in your exams and I will teach you how we use the table in other videos in the playlist I also go over how to do oxidation numbers the rules how to determine what is oxidized what is reduced how to write half reactions how to balance half reactions using the table and we look at different types of Redux reactions I hope to see you in another video very very soon bye everyone