Atoms- Smallest Unit of Matter

in this video, we're going to begin our lesson on Adam's, which are the smallest unit of matter now. The term matter is used by scientists to refer to anything that takes up space and has mass. So this includes all living organisms like me and you, but also non living things, too, like rocks and oceans and the device that you're watching this video through pretty much anything that takes up space and has mass will be matter. So matter is really, really, really broad, and it's going to be at the top here of our lesson. For that reason, it includes living and non living things now. All matter, regardless of if it's living or non living, is going to be made up of at least one chemical elements. And that's exactly what we're saying right here. It's gonna be made up of at least one chemical element. Now the term chemical element is defined as a pure substance that's made up of Onley, one type of Adam and so over here in our image, you can see that all matter is made up of at least one chemical element, and chemical elements are made up of atoms And so the Adam can therefore be defined as the smallest unit oven element now, because Adam's make up elements and chemical elements make up matter. We can also define the atom as the smallest unit of matter. And that's exactly what we're saying right here and up above and our title. Now, once again, Adams are going to make up both living and non living matter. So let's take a look down below at our example image to get a better idea of some of these concepts. So notice on the far left. Over here, we're showing you a new image of a diamond and of a honeybee in this plant. Now the diamond and the honeybee. Because they both take up space and have mass. They're both considered types of matter Now. The diamond, of course, is going to be non living matter, whereas the honey bee in the plant are going to be living matter. Now if we zoom into the diamond here, which you can see is the diamond structure that we're showing you over here, which is made up of all of these sees that we see here, and these seas represent a type of element. And so it's made up of just one type of element, which is the element carbon, which is abbreviated with just a C. Now, if we zoom into one of these chemical element symbols, one of these seas, which will see, is that it's made, uh, it is a carbon atom. And so here on the far right, we're showing you a representation of a carbon atom. Now, in our next video, we're going to talk Maura about the structures and properties of atoms. But for now, you should notice that the, uh, non living matter like diamond eyes gonna be made up of at least one chemical element. And the smallest part of a chemical element is going to be the atom itself now similarly down below with the honeybee and the plant. When we zoom into one of its chemical structures, you can see that it's going to have a sugar like, for example, glucose is a sugar that could be found in these living organisms, and which will notice is that this glucose structure over here actually has multiple types of elements. In fact, it has three types of elements. It has the same carbon element as the diamond. But then it also has the element oxygen and the element hydrogen, and you can see those throughout this glucose structure here. Now, if we zoom into just one of the calendrical elements of hydrogen here, which will see, is that the smallest unit of this element is a hydrogen atom, and so this is the representation of the hydrogen atom. And once again we'll talk more about the components of the atom and the properties of the atom moving forward in our course. But for now, this year concludes our introduction to how atoms are the smallest unit of matter. And once again, the biggest take away is that all matter is going to be made up of chemical elements. And the smallest unit of a chemical element is the atom. So I'll see you guys in our next video.

in this video, we're going to talk about atomic structure or the structure of atoms. Now, Adams are made up of three subatomic particles, each with their own characteristic charge mass and location within the atom. Now notice. Over here we have this table that gives you information on the three sub atomic particles that make up an Adam. And so those three subatomic particles are protons, neutrons and electrons. Now, when it comes to the electric charge of a proton, it's actually going to be plus one. So it has a positive charged. And so you can think that the P here in Proton is for the P and positively charged. Now, when it comes to the electric charge of the neutron, the neutron is going to be, as its name implies neutral, meaning that it has a neutral electric charge of zero, and so its electric charge is going to be zero. Now, when it comes to the electron and its electric charge, it's going to have a negative one electric charge. And so the way that you can think about it is electron kind of sounds like getting electrocuted, and getting electrocuted is definitely not something positive it's something negative, and that's how you can remember that it's gonna have a negative one charge. Now, when it comes to the mass of subatomic particles, the subatomic particles are so incredibly small that it doesn't really make a lot of sense to measure their mass in pounds or ounces or kilograms or grams. Even they're so small that the scientists have come up with a new unit to measure their mass. And that unit is called the Atomic Mass unit. Or am you for short Now, protons having Atomic Mass unit of one neutrons also have an atomic mass unit of one. However, electrons are going to be different. Electrons have a mass that is so incredibly small that it's practically negligible, meaning that we can pretty much ignore its mass and just round it off to say that it is zero and so we can go ahead and say that the electron has an atomic mass unit of zero. Now, in terms of the location of these subatomic particles within the atom, you can see that the proton is found within the nucleus of the atom. The neutron is also found within the nucleus of the atom however, the electrons once again are going to be different. Instead of being found within the nucleus, the electrons are going to be found orbiting the nucleus or revolving around the nucleus. And so, if we take a look at our image over here, you can see that we're showing you the image of a carbon atom right here. And notice that the nucleus is indicated with the purplish background. And so notice that within the nucleus we have these positively charged protons that look like this. And then we also have these neutral gray circles that represent the neutrons, and both the protons and the neutrons are found packed within the nucleus of the atom. Just like what we see here, however, noticed that the electrons which are these little blue circles, uh, they are not found within the nucleus. Instead, the electrons are going to be found orbiting the nucleus in these electron shells that we see here. Now, we'll talk more about these electron shells as we move forward in our course. But for now, what you guys should know are the subatomic particles are protons, neutrons and electrons. You should know their characteristic electric charge. Their characteristic atomic mass unit and the location of each subatomic particle. And so this year concludes our introduction to atomic structure, and as we move forward, we'll be able to get some practice, so I'll see you all in our next video.

all right. So here we have an example problem that wants us to fill in the sentence here, using one of these five potential answer options down below. And it says that negatively charged particles of Adams with almost no mass are called either electrons, protons, neutrons, ions or polymers. Now, so far, at this point in our course, we have not yet introduced ions or polymers. However, later in our course we definitely will talk about these two terms. But because we have not yet introduced these two terms, we should have been able to figure out that these two are not going to be the correct answer for this problem. So now we're between either electrons, protons or neutrons, which are the three sub atomic particles of a typical Adam recall that the P and protons can remind us that this subatomic particle is positively charged so you can think the P and protons is for the P and positively charged. And so because protons are positively charged, they're not going to be negatively charged, and so we can eliminate, answer, option beat and also recall that neutrons are, as their name implies, new troll and neutral means that it has a net charge of zero, and so it will not be negatively charged. It will have a charge of zero. So once again we can eliminate nutrients. And, of course, this Onley leaves the electrons, which is the correct answer for this example problem. And so electrons are negatively charged and recall that electrons kind of sounds like getting electrocuted and getting electrocuted is something negative. And so that can remind us that electrons are negatively charged. And also electrons have almost no mass. And so we can pretty much say that their mass is about equal to zero. And so we can go ahead and, uh, indicate that a Here is the correct answer to this example problem and that concludes this example. So I'll see you guys in our next video.

A proton ___________:

a) Has one positive charge.

b) Has one AMU.

c) Is found in the nucleus of the atom.

d) Only a and b are true.

e) a, b, and c are true.

• A. Has one positive charge.
• B. Has one AMU.
• C. Is found in the nucleus of the atom.
• D. Only a and b are true.
• E. a, b, and c are true.

in this video, we're going to talk about the elements of life. And so it's interesting to note is that of all of the known elements that exist in the universe on Lee, a small subset of those elements is found in living organisms. Now the periodic table of elements, which I'm sure you guys have probably heard of before in your previous courses eyes a table that arranges all of the known elements that exist based on their chemical properties. And so, if you take a look down below at our image, which will notices, we're showing you a periodic table of elements showing you all of the known elements that exist now. Once again, living things do not utilize all of these elements. Instead, they Onley utilize a small subset of them. In fact, about 97% of the mass of most living organisms, which is the vast majority of the mass, is made up of just six elements, which are carbon, hydrogen, nitrogen, oxygen, phosphorous and sulfur. And if you take the chemical symbols for each of these elements, it spells the word chin ops. And so if you can remember chin ops, then you'll be able to remember these six elements that make up the vast majority of most living organisms. And so because these six elements make up the vast majority of most living organisms, they're referred to as bulk elements, which we're showing you down below here in the periodic table. So notice that the bulk elements are highlighted in blue, and so you can see the positions of these six elements that make up the vast majority of life. And so these are once again going to be hydrogen, carbon, nitrogen, oxygen, phosphorous and sulfur. And so if you arrange them in the right way, it will spell out that word chin ups. Now, which will also notice, is that we've got these other elements that air highlighted in this yellowish color, and these are referred to as the trace elements. And so, as the name implies with trace elements, uh, these are required for life. However, there Onley required in trace amounts or in very, very small amounts. And so if you take a look down below notice once again that the trace elements that are required for life however they're required in very, very small amounts, uh, they are highlighted in yellow throughout our table here. And so you don't need to memorize all of these trace elements. Don't worry about doing that. Um, instead, what you should be aware is that there are some trace elements that are required in small amounts. And you should be familiar with more familiar with the bulk elements, which again you can remember just by remembering chin ups. And so this here concludes our lesson on the elements that are required for life and will be able to get some practice as we move along through our course. And so I'll see you all in our next video.

Alright. So here in this video, we're going to talk about some atomic properties and so each atom oven element has unique properties and we're going to talk about three specific properties that you all should be familiar with and we're going to talk about them in these three lines of text here. Now The very first property that you all should be familiar with is the atomic number. Now the atomic number is defined pretty simply. It's a pretty straightforward, easy idea. All it is is the total number of protons in the nucleus of an atom. And so all you need to do to get the atomic numbers count up the total number of protons and that's it. Now, the atomic number, or the total number of protons, is actually what defines each element. And so if we change the total number of protons in the nucleus of an atom, then we change the element that it falls under. However, if we change the other subatomic particles like neutrons or electrons, then we do not change the element and so on. Lee changing the number of protons or Onley changing the atomic number is going to change the element, and that's why the atomic number or the number of protons defines each element. So let's take a look at our example down below to clear some of this up. So here we're taking a look at the atomic properties of a carbon atom. More specifically, this carbon atom that we're showing you right over here. And so if we want to determine the atomic number, which is once again just the number of protons in the nucleus, all we need to do is count up the total number of protons in this nucleus over here. And so when we do that, what we'll see is that there are a total of six protons in the nucleus, which means that the atomic number of this Adam is six. And so, once again, the protons are here in red and we're just counting up the number of red circles here, and there are six of them, which is why the atomic number is six. So that's pretty straightforward. That's called the atomic number. Now, once again, if we were to add 1/7 proton in here, uh, then we would be changing the element and it would no longer be carbon. Instead, it would be nitrogen. And so the number of protons in the nucleus is going to define the element. Now, if we were to add another neutron here, pretend this were a gray circle. If we were to add another neutron, then it would still be a carbon. Adam, if we were to add another electron here in, uh, the, uh, revolving around the nucleus, Uh, then it would also still be a carbon atom. And so the number of electrons and neutrons do not affect the type of element that it iss. And once again, it's on Lee the number of protons that determines, uh, each element, and so that really that's it for the atomic number moving on. Now. What we have next is the mass number, and the mass number is also a pretty straightforward idea. It's really just the mass of the nucleus of a single Adam. And so if we want to take the mass of the nucleus, then we need to consider the subatomic particles that air inside of the nucleus, which we know are both protons and neutrons as well. And so the mass number is going to be the total number of protons and neutrons found in the nucleus. So once again, let's take a look at our example down below on DSO Of course, if we want to get the mass number, we need to get the mass of the nucleus and consider the number of protons and neutrons in the nucleus. We already know the number of protons. And so if we count the number of neutrons, the number of gray circles here in the nucleus, what you'll count is that there are a total of 612345 and six. So we can put a six here as well. And so if we want the mass number, all we need to do is total Up to two, we have six protons plus six. Uh, neutrons will give us the mass. Number six plus six is, of course, equal to 12. And so this is going to be the mass number that we just defined up above here now, last but not least, what we have here is the atomic mass, which is also sometimes referred to as the atomic weight. Now, the atomic mass or the atomic weight sounds kind of similar to this mass number idea, and really, they are very, very similar. However, there's one big difference, and this is the idea that the atomic mass or the atomic weight instead of being the mass of the nucleus of one Adam, it's actually going to be an average total mass of all of the atoms of an element. And so it is going to be an average. Whereas the mass number is not an average, it's the mass of just one Adam. Now, if we take a look at our image over here on the right hand side, which you'll notice is that a lot of periodic tables in your textbooks are gonna have a periodic table view that looks somewhat like this for the elements. And so when you see this view here, you'll notice that there are some specific labels here. Now, the very first one that you'll see here is this number up here, which is 12.11 now. This number here is what we refer to as the atomic mass or the atomic weight that we just talked about, which is once again an average total mass of all of the atoms of an element which is why it looks like a strange number here with the 0.11 Um and so once again, we'll be able to understand this idea here of atomic mass or atomic weight, much better later in our course, once we start talking about isotopes. But for now, what you should note is that the atomic mass is going to be very, very similar to the mass number of 12. Notice that they're very, very close. But they're going to be slightly different because once again, the atomic masses an average and we'll be able to understand that idea better in a different video once we talk about is Atos. Now notice that what we also have in here is the atomic number and the atomic number tells us the total number of protons in the nucleus, which we know is, ah, six here for the carbon atom. You'll also note that the chemical symbol is always going to be shown here for carbon. The chemical symbol, a C and the element name is usually provided as well, which is carbon. And so this year concludes our introduction to thes atomic properties of atomic number, mass number and atomic mass or atomic weight, and we'll be able to get some practice applying these concepts moving forward in our course, so I'll see you all in our next video.

all right. So here we have an example problem that once it's the complete the sentence here, using one of these five potential answer options down below. And it says that the atomic number of an element is equal to the number of neutrons, Onley, neutrons, plus electrons, protons plus electrons, protons, Onley or protons, plus neutrons. Now, of course, we know from our last lesson video that the atomic number is going to be exactly equal to the number of protons Onley that air found in the nucleus. And so this here is our atomic number, and it is the correct answer to this example. Problem. Now, of course, protons plus neutrons might sound familiar, but that's because this is referring to the mass number or the mass of the nucleus of an atom. But it's not the same thing as the atomic number, so that's why it's not correct. The protons plus electrons are going to dictate the net charge of the atom because, remember, protons are positively charged and electrons are negatively charged. And so the balance of protons and electrons, which are opposite Lee charged, is going to dictate the overall net charge of the atom But once again, Option B here is not going to be the atomic number. And then neutrons only And neutrons plus electrons. They once again are not gonna be the atomic number. So that concludes this example problem. And I'll see you in our next video.

The average oxygen atom has a mass number of 16 and an atomic number of 8. This means that the number of neutrons in this oxygen atom is:

a) 24.

b) 8.

c) 16.

d) 4.

e) 2.

• A. 24.
• B. 8.
• C. 16.
• D. 4.
• E. 2.

in this video, we're going to continue to talk about Adams by focusing on their electron, orbital's and energy shells. Now, electron orbital's are really defined as three dimensional regions or three D regions around the nucleus of an atom where electrons can be found now. Although electron orbital's are three dimensional regions, they can still be envisioned in two dimensions or in two D. As energy shells and really an hour course were mainly going to focus on the energy shell aspect, you'll learn Maura about the three dimensional shapes of electron orbital's in a chemistry class. So let's take a look down below at our example image here of the carbon atom on the far left to get a better understanding of these idea of this idea of energy shells. And so, which will notice, is that the chemical symbol here, right in the middle, represents the nucleus of this carbon atom, but then revolving around the nucleus of the carbon atom. What we have are these black circles, two of them, for that matter that represent energy shells. And once again, energy shells are really just the two D representation of the electron orbital's, which are really three dimensional regions. And so the energy shells once again are going to contain electrons. And so these little circles blue circles that you see around here are the electrons that are revolving or orbiting around the nucleus of the atom in these energy shells. Now, once again, any typical Adam could have multiple energy shells, as you can see from our image down below. And so if we focus in on the carbon atom here, notice that it has to energy shells once again has the one that is right here that is closer to the nucleus. And then it has a second energy shell that is further away from the nucleus. And so it's important to note is that the energy shelves that are closer to the nucleus of the atom are actually going to be lower and energy than the energy shells that arm or distant from the nucleus. And so, of course, this means that the distant shells that air further away from the nucleus are going to be higher and energy. And so because these distant shells are higher and energy, those are the ones that are mawr reactive, and so those are the ones that scientists tend to focus most of their attention on when they're looking at chemical bonds, which we'll talk about chemical bonds mawr later in a different video. But when we take a look at this carbon atom down below, notice once again that the energy shell that is furthest away from the nucleus is gonna be the one that is highest and energy, and it's gonna be the one that is more reactive and the one that tends to form chemical bonds. Now this leads us to this idea of valence electrons, because valence electrons are defined as the electrons that are found in the outermost energy shell, basically in the energy shell that is furthest away from the nucleus and the energy show that is furthest away from the nucleus. We can also call the Valence shell, And so the valence shell for carbon would be this one that is for this, away from the nucleus and electrons that are found within the valence shell. Like these four that we see here are termed valence electrons. And those were the once again the ones that are higher and energy and the ones that arm or reactive and so the other. Electrons that are closer to the nucleus are not as high and energy, and they're not nearly as reactive. And so they're not going to be the ones to form chemical bonds with other atoms. So that's important to keep in mind. Now, if you take a look down below the Adam, what you'll find is a different way to represent these atoms. And so you can see that the chemical symbol is gonna be shown here and then up to the top left of the chemical symbol. What we can show is the mass number which recall from our previous lesson videos, is just the total number of protons and neutrons and then to the bottom left of the chemical element. What we can show is the atomic number, which recall from our previous lesson videos, is the total number of protons in the nucleus. And so you can see that, uh, the carbon atom here has six protons in its nucleus which aren't being shown. They're just being symbolized here with the letter C, but then it also has six electrons that are negatively charged and balance out the positively charged protons. And so that means that the carbon atom that's being shown here is going to have a neutral net charge because the number of protons, which again is equal to six, balances out with the number of electrons, which is also equal to six when we count them up here. And so it has a neutral net charge and in fact all of the atoms that we're showing you right here are all going to have a neutral net charge as shown. So that's something important. Also keep in mind now, in terms of the first energy shell, the first energy shell is always going to hold a maximum of two electrons. The second energy shell is going to hold a maximum of eight electrons and then each of the shells that are beyond that are all going to hold a varying number of ah characteristic number of electrons and really, for our purposes, in this biology course, you really only need to know. The first electron holds up to two electrons and the second shell holds up to eight electrons. Sorry, The first shell holds up to two electrons, and the second shell holds up to eight electrons. So if we take a look down below the carbon atom once again notice that the first energy show here is holding a maximum of two electrons. And any additional electrons need to be in a different energy shell. And so this is going to be how we can represent the carbon atom with its energy shells like this. If we move on to the hydrogen atom right here, what you'll see is that its atomic number is one meaning it has one proton on its mass number appears also one which means that it only has one proton and no neutrons. And of course, because all of the atoms that we're showing you here are neutral, uh, have a neutral charge. The number of protons is gonna bounce out exactly what the number of electrons for all of the ones that are shown right here. And so if it has one proton, that means it also has one electron. And because it only has one electron, it only needs one energy shell. And so this is a way to represent the hydrogen atom now moving on to the nitrogen atom. Nitrogen atoms have seven protons in their nucleus. And so when we count up the number of electrons. You'll see that there are also seven electrons to balance out the positively charged protons. And so, for its energy shell noticed that it gets filled. The first energy shell gets filled with two electrons, and then all of the other electrons need to make their way into the third. Um, sorry, the second shell, which holds up to a maximum of eight electrons. Um, now, if we move on to the oxygen atoms, Oxygen has a characteristic atomic number of eight, and so its mass number is 16, which means it has eight neutrons in its nucleus. But once again you can count up the total number of electrons it's going. It's going to add up to the total number of protons if it's a neutral oxygen atom, which once again these are all neutral atoms. And so, which will see once again, is that the first two electrons are gonna go into the first energy shell, and then all other electrons are gonna move to the second shell, which can hold up to a maximum of eight electrons. And here it holds six electron, so it's fine. However, once we go to the phosphorus atom over here. Uh, notice that its atomic number is 15, meaning it has 15 protons in its nucleus. It's mass numbers 31 meaning it has 16 neutrons in its nucleus. But once again, because these air neutral atoms, the number of protons here eyes gonna equal the number of electrons. So when you count up all of the electrons here, you'll count that there are 15 of them. Once again, the first energy shell is filled with two electrons. Eso then it goes on to the second shell, and the second shell is filled with eight electrons. So that means that all of the other electrons need to move into the third shell here. Um and, uh, the sulfur atom over here is a similar example. It it's going to have a atomic number of Ah, mass number of 32 which means it has 16 neutrons in its nucleus. And then, of course, the number of electrons that you see revolving around the nucleus is going to match the number of protons if it's a neutral atom. And once again the first shell gets filled with two electrons, the second shell gets filled with eight electrons and all of the other electrons gonna need to move into the third shell here for this sulfur. And so this year really concludes our lesson on electron, orbital's and energy shells, and we'll be able to get some practice applying these concepts moving forward in our next few videos, so I'll see you in our next one.

How many valence electrons does an atom with five total electrons have?

a) 5.

b) 7.

c) 3.

d) 2.

e) 1.

• A. 5.
• B. 7.
• C. 3.
• D. 2.
• E. 1.

Which of the following is true about electron energy shells?

a) They represent regions around the nucleus in which the electrons orbit.

b) The shells closest to the nucleus contain electrons with higher energy.

c) They contain electrons of the same energy.

d) a and b only.

e) a and c only.

• A. They represent regions around the nucleus in which the electrons orbit.
• B. The shells closest to the nucleus contain electrons with higher energy.
• C. They contain electrons of the same energy.
• D. a and b only.
• E. a and c only.

in this video, we're going to introduce the octet role Now. The octet role is really just a roll of thumb that says that Adam's arm or stable and less reactive when their valence shells are fully occupied. And so recall from our last lesson video that the first energy shell will hold up to a maximum of just two electrons. But the second energy shell will hold up to a maximum of eight electrons. And really, this eight electron maximum is where this octet is coming from with the octet role. And most of the simple atoms that will be talking about an hour biology course are going to apply to this octet role. But really, the main take away here of the octet rule is that Adams Air going to be less reactive when their outer valence shells are fully occupied are full. So let's take a look at our image down below to get a better idea of this octet role, and so notice that here in the middle, what we have is an electron thes little blue circles that you see throughout our image represent electrons, and so this represents some electron that wants to react And so what you'll see is that on the left we have an Adam, and on the right, we have another Adam. And so what you'll notice is that the dinner table here with the Thanksgiving turkey represents the nucleus of these atoms and then revolving around the nucleus. What we have are the electrons. And so we're specifically focusing on the second energy shell here, which we know holds up to a maximum of eight electrons and so notice that the electrons that have an open slot in their energy shells are going to be more likely to react. And so you can see that this Adam over here because it does have an open slot that's available, it says, Yeah, there is a spot for you here, and so it will react with other electrons from other atoms. However, this Adam over here notice has a full octet of electrons. And because it is full, it says, Nope, Werfel, and they do not react with other electrons from other atoms. So the idea, once again, is that Adam's gonna be less reactive when their valence shells are full, like this one has a full octet and its second shell, so it's going to be much less reactive, and it will not react with other electrons that want to react. And so really, that's the main take away here of the octet rule, and we'll be able to get a little bit of practice in our next few videos, so I'll see you guys there.

all right. So here we have an example problem that says, According to the octet role, electron distribution in each shell of a neutral nitrogen atom with an atomic number of seven is which one of these four potential answer options down below, where the first number of each answer option suggests the total number of electrons in the first energy shell. And the second number of each answer option represents the total number of electrons in the second energy show. And so really, what we need to do is draw ourselves a little sketch of a neutral nitrogen atom, which once again has an atomic number seven. So let's go ahead and say that this green circle here represents the nucleus of our nitrogen Adam, which once again we know, has an atomic number of seven. So we know that it has seven positively charged protons in its nucleus. But then it tells us that the nitrogen atom is neutral, which means that it's going to have an overall net charge of zero, which means that the positively charged protons are gonna be balanced out perfectly with the number of negatively charged electrons. So if there are seven positively charged protons. There must be seven negatively charged electrons in order to make this nitrogen atom neutral. So we have to draw a total of seven electrons. So considering that we could go ahead and draw our first energy shell and we know that the first energy shell holds a maximum of two electrons. So we could go ahead and fill this first energy shell here with two electrons, as we see here. And then the other electrons need to go into the next shell so we could go and draw our second energy shell. And of course, we can put the remaining electrons here, so we know that there must be a total of seven electrons. We've already got two. So we gotta put five Maurin the second shell, so we could go ahead and put four and five electrons in this outer shell. So once again, there is a total of seven electrons here that balance out the seven protons, which makes this nitrogen atom neutral. And so now we need to do is take a look at the answer options. And once again we can see that the first energy shell here has a total of two electrons, not one electron as option A and option D indicate, so we can go ahead and eliminate. Answer, option A and answer option D Just based on that. However, when we look at answer option B and answer option C, notice that they both suggest the first energy shell has two electrons, which once again is correct. We could see the first energy shell does have two electrons. So then we need to look at the second number, which is really how these two answers differ, and you can see that the second energy shell when you count them up. There's a total of five electrons, not for electrons, so we can go ahead and eliminate. Answer. Option B. Here we can eliminate answer option B and go ahead and indicate that his answers options. See here that is the correct answer for this example problem, and the reason for that is once again, the two here indicates the number of electrons in the first energy shell, which you can see. There's one here and the other is right here, and then the second number of five indicates the number of electrons in the second energy shell. And once again, there are five when you count those up and so see, here is the correct answer to this example, and I'll see you guys in our next practice video.

A neon atom (Ne) is unreactive for which of the following reasons?

a) It has 7 valence electrons.

b) It has 8 valence electrons.

c) Its valence shell is full of electrons. 

d) It has 20 valence electrons.

e) b and c only.

• A. It has 7 valence electrons.
• B. It has 8 valence electrons.
• C. Its valence shell is full of electrons.
• D. It has 20 valence electrons.
• E. b and c only.

How many electrons does an Oxygen atom need to fulfill the octet rule by filling its valence shell?

a) 8.

b) 4.

c) 1.

d) 2.

e) 6.

• A. 8.
• B. 4.
• C. 1.
• D. 2.
• E. 6.