Hello students. This is a short little video on the elements and the periodic table. As you've already had chemistry, this should just be a little bit of a review on that, but we're going to focus on how the elements are um arranged and their characteristics and the periodic table. So remember, the atomic number is the number of protons in the nucleus. And so the number of protons determines the element. If I change the number of protons, I change the element. And so when we look at the periodic table, as you go from box to box to box, what is changing is the number of protons every time. And so the atomic number is the number of protons for that element. Okay, that is very important. So elements are substances that can't be broken down into simp simpler substances by chemical means. So we're not going to we're basically they're into their atoms and that's it. So you're not breaking them beyond that. And that's very important. So the periodic table is an arrangement of these elements based on their chemical properties and they're arranged into groups and they have specific symbols. So their symbols are abbreviations. The symbols are usually based on um their name and their name can be from their Latin name or it can be from the name that they have. So it just depends on what what's being used. So make sure you pay attention to that when we look at the groups. So, we're not going to spend a lot of time on this because you've had chemistry, but the things that we're going to focus on for physio are the elements that we use that are in the human body. We'll we'll spend a lot of time on hydrogen because hydrogen is very important in the human body. We'll spend time on carbon, nitrogen, and oxygen. So, these are probably if I have to list like the big four, these are the big four molecules. Carbon, hydrogen, and oxygen are in all your macroolelecules. Nitrogen are in two of your macroolelecules, your nucleic acids and your proteins. So those are the big four major major elements that are in the b human body. And then we'll talk about some other elements that are very important like sodium here. And this is based on natrium, which is the the Latin name for sodium. And then potassium, which is the the symbol K. Here you've got calcium. We'll talk a little bit about magnesium, but we'll spend a lot of time with sodium, potassium, and calcium. Um, we'll talk about iron when it comes to blood because this is the in the heem group for our red blood cells in the hemoglobin. Copper and zinc are some trace minerals that we talk about a little bit. Selenium a little bit. Sulfur a little bit. There's sulfur bonds in your proteins. Phosphorus very important. Calcium and phosphate um go together and they'll be important for bone mineralization. Um phosphates also very important um in our macroolelecules and um also ATP adenazine triphosphate. So these will be the major elements that we'll be focusing on in our class. When we look at the different groups and looking at the periodic table, note that when you think about the shells and the electrons and the arrangement, this first column here, everybody in this first column actually has one electron in their outer shell. That's a little cheat sheet for you. Everybody in the second column here, the second group has two electrons in their outer shell. Another cheat sheet. This group here, 3A, three electrons in the outer shell. Four, four electrons in the outer shell. Five, five electrons in the outer shell. Six, six electrons in the outer shell. Seven, seven electrons in the outer shell. Eight, eight electrons in the outer shell. So that tells you right there um other than the top ones, this one has one and this one has two because they only have one or two electrons. But for the most part, that's telling you about the reactivity of the these groups. So if you note that this this group all only has one in their outer shell, you know that to be full, they either want to give up one and so they go back to their next full shell or they gain seven. Well, it's really hard to gain seven or share seven. So it's easier just to give one up. So most of the time these guys are giving up electrons and that's where we'll tend to form ions. And that we'll talk about when we get to ionic bonds. We'll talk about that. But that's why they tend to form ions is they tend to give up their electrons because it's easier to give one up and be full than to get seven. And again, the goal is to be full, right? To be satisfied and have that full outer shell full. And for this group here, remember they have two in their in their outer shell. So they tend to give up two rather than gain six, right? And when we get over here, this group has three in the outer shell, so they might give up three. Um, this group has four. So giving up four or gaining four is very hard. Usually they're sharing they're sharing bonds for the most part. Nitrogen. Now this group, this group five has five in their outer shell. So now we're going to where they're more likely to accept electrons or share electrons and because there's there's only they only need a few, right? So to fill their outer shell, they're going to take some in or share some to fill that outer shell. And again, if they have five in their outer shell, how many do they need to be full? They need three more, right? So they're going to form three bonds or and to get three to share three three pairs of electrons. Um oxygen has six in the its outer shell. So it only needs two more. So it's either going to gain two electrons or share two two pairs, right? Um, so and then fluoride, same thing. One, these guys typically are missing one, so they usually pick one up. It's easy to pick one up or share one. And this group, remember, this group has two or eight in its outer shell. So they they are full. They tend to not want to react with anybody. These are your noble gases. They don't tend to interact with anybody else. So when we talk about reactivity and why thing why certain atoms react with others it's going to be determined by their veence shell that outer shell and the number of electrons that are there. Also, another important thing that I want you to pay attention to as far as the arrangement, we're not going into we're not doing all of chemistry in this class because we don't have time, but kind of dialing it down, is that this upper right corner of the periodic table has the most electro negativity compared to this lower leftand corner. So this side of the periodic table is less electro negative. This upper right hand corner is most electrogative most electrogative. What that means is that electro negativity means the the desire to hold on to electrons, the desire to keep electrons. So this fluoride is always wanting to pull electrons towards itself or keep electrons. So it's more likely to take electrons from somebody that is over here rather than share because it's very strongly going to pull them towards towards itself. And these guys don't really these guys have very low electro negativity. So they're they're willing to just give them up rather than hold on to it. But if you have two elements that are over here and they're both, you know, sharing electrons, they have different electro negativities, but one is stronger than the other. So, one might pull it more than another. And so, you're going to have an unequal sharing of electrons. We'll talk about that again in our next lecture as far as um polar bonds. But this is important to understand that there can be different attractions to those electrons and it's based on like it you can determine that by their location on the periodic table. So this upper right hand corner very electrogative over here poorly electrogative hydrogen very poorly does not hold on to electrons at all. It's like just take them you can have them. Okay. So, um, keep that in mind when we talk about reactions and and interactions throughout our course. And they'll the transfer of electrons is very very important. And so, we'll be we'll be talking about this pretty much all semester. Okay. So, in the human body, we have hydrogen, oxygen, carbon, and nitrogen. These are four major elements. You saw those on the periodic table. They they are in within specific groups. We're going to work on these in lab first week. You're going to draw these out. You should know what the veilent shell is for each of these. You should know what the atom is. You should know the atomic number. There are some trace um elements and some minerals that we'll talk about in the class. You don't have to memorize those, but and don't memorize the percentages in the body. This is just for your reference and just for you to look at and say, "Oh, wow. That's really cool to think about." Um, but this is just to show you how much of that is in our body. There's a lot of oxygen in the body because we carry oxygen and because there's a lot of water in the body and so that takes up a major part of the body. and then carbon because most of our molecules are made our organic molecules are made up of carbon and so those are major components of our body. So carbon, hydrogen and nitrogen are most of the body and so we'll spend a lot of time talking about these elements. Remember the mass number. So the mass number what contributes to mass protons and neutrons. So your mass number will be the protons and the neutrons. Electrons don't really contribute because they're super tiny. Isotope. An isotope is a is an atom is an type of element. So same element but with a different mass number. So they have a different number of neutrons not protons because if it was protons it would be a different element altogether. So it has to be the same element with a different number of neutrons. Okay? And so that is an isotope. Isotopes can be stable or they can be unstable. Unstable isotopes are like, you know, kids jazzed up on candy. They have to get rid of this energy to become stable again. And so they release this energy and that energy um releases called radioactive decay. And that energy is damaging. That's radiation. That's what we call radiation. And that radiation damages DNA. And so it can be harmful. We can also use it for imaging, which we talked about in our last chapter. But this is this is what radioisotopes are. They emit energy to become stable because they are unstable in their isotope form. So examples of this, you've got proteium, dutyium, and tridium. And each of these is unstable. And so they're they have a they're emitting energy to become stable. And so here's an example of a PET scan. We saw this in our imaging lecture. And you can see this is being detected by the computer or the imaging software and that's highlighting the areas that are taking up that tracer there. So our next lecture is going to be on chemical bonds and these are going to be determined by good the veence electrons. So the type of chemical bond will be determined by the veilance shell and what we've got going on there and the element that we have. So we'll talk about that in our next lecture. We'll see you there.