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1
concept
Atoms- Smallest Unit of Matter
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5m
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In this video we're going to begin our lesson on atoms 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 nonliving things. Now all matter, regardless of if it's living or nonliving is going to be made up of at least one chemical element 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 only one type of atom. 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 atom can therefore be defined as the smallest unit of an element. Now because atoms 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 in our title. Now once again, atoms are going to make up both living and nonliving 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 an 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 honeybee and 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 c's that we see here. And these c's 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 c's, what you'll see is that it's made 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 more about the structures and properties of, atoms. But for now, you should, notice that the, nonliving matter like diamond, is 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 can be found in these living, organisms. And what you'll notice is that, this glucose structure over here actually has multiple types of elements. In fact, it has 3 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 in to just one of the chemical elements of hydrogen here, what you'll 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 here concludes our introduction to how atoms are the smallest unit of matter. And once again the biggest takeaway 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.
2
concept
Atomic Structure
Video duration:
4m
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In this video, we're going to talk about atomic structure or the structure of atoms. Now, atoms are made up of 3 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 3 subatomic particles that make up an atom. And so those 3 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 1, so it has a positive charge. And so you can think that the p here 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 0, and so its electric charge is going to be 0. 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 kinda 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 AMU for short. Now protons have an atomic mass unit of 1. Neutrons also have an atomic mass unit of 1. 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 a 0. And so we can go ahead and say that the electron has an atomic mass unit of 0. 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, notice that the electrons, which are these little, blue circles, 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, our 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 here 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.
3
example
Atoms- Smallest Unit of Matter Example 1
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2m
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Alright. So here we have an example problem that wants us to fill in the sentence here using one of these 5 potential answer options down below. And it says that negatively charged particles of atoms 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 2 are not going to be the correct answer for this problem. So now we're between either electrons, protons, or neutrons, which are the 3 subatomic particles of a typical atom. Recall that the p in protons can remind us that this subatomic particle is positively charged. So you can think the p in protons is for the p in positively charged. And so because protons are positively charged, they are not going to be negatively charged, and so we can eliminate answer option b. And also recall that neutrons are as their name implies neutral, and neutral means that it has a net charge of 0 and so it will not be negatively charged, it will have a charge of 0. So once again, we can eliminate neutrons. And of course, this only leaves the electrons, which is the correct answer for this example problem, and so electrons are negatively charged and recall that electrons kinda 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 0. And so, we can go ahead and, 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.
4
Problem
Problem
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.
5
concept
Elements of Life
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3m
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Video transcript
In this video, we're going to talk about the elements of life. And so what's interesting to note is that of all of the known elements that exist in the universe, only 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, is 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, what you'll notice is 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 only 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 6 elements which are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. And if you take the chemical symbols for each of these elements, it spells the word CHNOPS. And so if you can remember CHNOPS, then you'll be able to remember these 6 elements that make up the vast majority of most living organisms. And so because these 6 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 6, elements that make up the vast majority of life. And so these are once again, going to be hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulfur. And so, if you arrange them in, the right way it'll spell out that word CHANOPS. Now what you'll also notice is that we've got these other elements that are highlighted in this yellowish color and these are referred to as the trace elements. And so as the name implies with trace elements, these are required for life. However, they're only 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, 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. 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 CHNOPS. And so this here concludes our lesson on the elements that are required for life and we'll be able to get some practice as we move along through our course and so I'll see you all in our next video
6
concept
Atomic Properties
Video duration:
7m
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Video transcript
Alright. So here in this video, we're going to talk about some atomic properties. And so each atom of an element has unique properties, and we're going to talk about 3 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 number is 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 only changing the number of protons or only 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 6 protons in the nucleus, which means that the atomic number of this atom is 6. 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 6 of them, which is why the atomic number is 6. So that's pretty straightforward. That's called the atomic number. Now once again, if we were to add a 7th proton in here, 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 atom. If we were to add another electron, here in, the revolving around the nucleus, 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 is. And once again, it's only the number of protons that determines, 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 atom. And so if we want to take the mass of the nucleus, then we need to consider the subatomic particles that are 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. And so 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 6. 1, 2, 3, 4, 5, and 6. So we can put a 6 here as well. And so if we want the mass number, all we need to do is total up the 2. We have 6 protons plus 6, neutrons will give us the mass number 6 plus 6 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 1 atom, 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 atom. Now if we take a look at our image over here on the right hand side, what 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 12.011. 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 all of the atoms of an element, which is why it looks like a strange number here with the point 011. And so once again, we'll be able to understand this idea here of atomic mass or atomic weight much bet 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 mass is an average. And we'll be able to understand that idea better in a different video once we talk about isotopes. 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, 6 here for the carbon atom. You'll also note that the chemical symbol is always going to be shown here. For carbon, the chemical cell symbol is c, and the element name is usually provided as well, which is carbon. And so this here concludes our introduction to these 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.
7
example
Atoms- Smallest Unit of Matter Example 2
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1m
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Video transcript
Alright. So here we have an example problem that wants us to complete the sentence here using one of these 5 potential answer options down below. And it says that the atomic number of an element is equal to the number of neutrons only, neutrons plus electrons, protons plus electrons, protons only, 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 only that are 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 oppositely 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.
8
Problem
Problem
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.
9
concept
Electron Orbitals & Energy Shells
Video duration:
9m
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Video transcript
In this video we're going to continue to talk about atoms by focusing on their electron orbitals and energy shells. Now electron orbitals are really defined as 3 dimensional regions or 3 d regions around the nucleus of an atom where electrons can be found. Now although electron orbitals are 3 dimensional regions, they can still be envisioned in 2 dimensions or in 2 d as energy shells. And really in our course we're mainly going to focus on the energy shell aspect. You'll learn more about the three-dimensional shapes of electron orbitals 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, what you'll notice is 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, 2 of them for that matter, that represent energy shells. And once again, energy shells are really just the 2 d representation of the electron orbitals, 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, atom 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 2 energy shells. Once again, it 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 what's important to note is that the energy shells that are closer to the nucleus of the atom are actually going to be lower in energy than the energy shells that are more distant from the nucleus. And so of course this means that the distant shells that are further away from the nucleus are going to be higher in energy. And so because these distant shells are higher in energy, those are the ones that are more 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 more 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 in 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 shell 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 furthest away from the nucleus. And electrons that are found within the valence shell like these 4 that we see here are termed valence electrons, And those are the once again, the ones that are higher in energy and the ones that are more reactive. And so the other electrons that are closer to the nucleus are not as high in 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 atom, 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, the carbon atom here, has 6 protons in its nucleus which aren't being shown, they're just being symbolized here with the letter c, but then it also has 6 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 6, balances out with the number of electrons, which is also equal to 6 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 to also keep in mind. Now in terms of the first energy shell, the first energy shell is always going to hold a maximum of 2 electrons. The second energy shell is going to hold a maximum of 8 electrons. And then each of the shells that are beyond that are all going to hold a varying number of, a 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 2 electrons and the second shell holds up to, 8 electrons. Sorry. The first shell holds up to 2 electrons and the second shell holds up to 8 electrons. So, if we take a look down below at the carbon atom once again, notice that the first energy shell here is holding a maximum of 2 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 1, meaning it has 1 proton, and its mass number up here is also 1, which means that it only has 1 proton and no neutrons. And of course because all of the atoms that we're showing you here are neutral, have a neutral charge, the number of protons is gonna balance out exactly with 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, 7 protons in their nucleus And so when we count up the number of electrons, you'll see that there are also 7 electrons to balance out the positively charged protons. And so for its energy shell, notice that it gets filled the first energy shell gets filled with 2 electrons and then all of the other electrons need to make their way into the 3rd, sorry, the second shell, which holds up to a maximum of 8 electrons. Now if we move on to the oxygen atom, oxygen has a characteristic atomic number of 8. And so, its mass number is 16 which means, it has 8 neutrons in its nucleus. But once again, you can count up the total number of electrons. It's gonna 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, what you'll 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 8 electrons. And, here it holds, 6 electrons, so it's fine. However, once we go to the phosphorus atom over here, notice that its atomic number is 15, meaning it has 15 protons in its nucleus. Its mass number is 31, meaning it has 16 neutrons in in its nucleus. But once again because these are neutral atoms, the number of protons here, is 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 once again, the first energy shell is filled with 2 electrons. So then it goes on to the 2nd shell, and the 2nd shell is filled with 8 electrons. So that means that all of the other electrons need to move into the 3rd shell here. And, the sulfur atom over here is a similar example. It it's going to have a atomic number of 16, a mass number of 32, which means that 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 2 electrons, the second shell gets filled with 8 electrons, and all of the other electrons are gonna need to move into the 3rd shell here for this sulfur. And And so this here really concludes our lesson on, electron orbitals 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.
10
Problem
Problem
How many valence electrons does an atom with five total electrons have?
A
5.
B
7.
C
3.
D
2.
E
1.
11
Problem
Problem
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.
12
concept
Octet Rule
Video duration:
2m
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Video transcript
In this video, we're going to introduce the octet rule. Now, the octet rule is really just a rule of thumb that says that atoms are more 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 2 electrons, but the second energy shell will hold up to a maximum of 8 electrons and really this, 8 electron maximum is where this octet is coming from with the octet rule. And most of the simple atoms that we'll be talking about in our biology course are going to apply to this octet rule. But really, the main takeaway here of the octet rule is that atoms are 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 rule. And so notice that here in the middle what we have is an electron this these 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 will see is that on the left we have an atom and on the right we have another atom, 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 8 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 atom 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 atom over here notice has a full octet of electrons and because it is full it says nope we're full and they do not react with other electrons from other atoms. So the idea once again is that atoms are gonna be less reactive when their valence shells are full. Like this one has a full octet in 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 takeaway 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.
13
example
Atoms- Smallest Unit of Matter Example 3
Video duration:
3m
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Video transcript
Alright. So here we have an example problem that says according to the octet rule, electron distribution in each shell of a neutral nitrogen atom with an atomic number of 7 is which one of these 4 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 shell. 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 7. So let's go ahead and say that this green circle here represents the nucleus of our nitrogen atom, which once again we know has an atomic number of 7, so we know that it has 7 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 0, which means that the positively charged protons are gonna be balanced out perfectly with the number of negatively charged electrons. So if there are 7 positively charged protons, there must be 7 negatively charged electrons in order to make this nitrogen atom neutral. So we have to draw a total of 7 electrons. So considering that we can go ahead and draw our first energy shell, and we know that the first energy shell holds a maximum of 2 electrons. So we can go ahead and fill this first energy shell here with 2 electrons as we see here, And then the other electrons need to go into the next shell. So, we can go ahead 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 7 electrons. We've already got 2, so we got to put 5 more in the second shell. So we can go ahead and put 1, 2, 3, 4, and 5 electrons in this outer shell. So once again, there's a total of 7 electrons here that balance out the 7 protons which makes this nitrogen atom neutral. And so now all 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 2 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 2 electrons, which once again is correct. We can see the first energy shell does have 2 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 5 electrons not 4 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 option c here that is the correct answer for this example problem. And the reason for that is once again the 2 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 5 indicates the number of electrons in the second energy shell. And, once again, there are 5 when you count those up. And so c here is the correct answer to this example, and I'll see you guys in our next practice video.
14
Problem
Problem
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.
15
Problem
Problem
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.
Do you want more practice?
We have more practice problems on Atoms- Smallest Unit of Matter