The atom represents the basic functional unit in chemistry
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concept
The Atom
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Now, the atom represents the smallest part of an element, and it's the basic functional unit in chemistry. We're going to say that it consists of 4 major parts. Now, in actuality, there are other parts to the atom, but we're not gonna mention them because they're beyond the scope of this class. If you ever decide to go into higher levels of chemistry, you'll worry about them then. But for right now, when it comes to general chemistry, let's just worry about these four portions of the atom. The first part, which is outlined by this orange circle within this image of the atom, it's the nucleus. Now, the nucleus isn't really that large. I've blown it up so that we can see what's inside of it. We're gonna say the nucleus represents the center of an atom that possesses the 2 subatomic particles, our neutrons, which we show as red, so these red circles here are our neutrons, and our protons, which are symbolized by these blue spheres here. Now we're gonna say the neutrons themselves, they're the subatomic particles that carry no charge, and, of course, are found within the nucleus. And the protons themselves are the subatomic particles that carry a positive charge and are found within the nucleus. So within this image, we have 1, 2, 3, 4, 5 protons. And we have 1, 2, 3, 4, 5, 6 neutral neutrons. Now what's swirling around the nucleus, we have these small little green spheres. These are the smallest subatomic particles, the electrons, that carry a negative charge, and of course they spin around the nucleus. So when it comes to our atom itself, it's the smallest part of an atom. It's consisting of 4 parts. Basically, the nucleus houses the protons and neutrons with the electrons spinning around the nucleus. We'll go into greater discussions about how these electrons move in later chapters. But for now, just focus on these 4 primary portions of the atom.
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example
The Atom Example 1
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So if we take a look at this example question, it says, which of the following statements is true? 1st, a, protons and electrons have charges of the same magnitude, but opposite signs. Well, we said that protons are positively charged and electrons are negatively charged, so they definitely have opposite signs. We could think of a proton as having a plus one charge and an electron having a minus one charge. So their magnitudes, basically the number assigned with the charge, they're the same. They're 1. Right? Plus 1 minus 1. So the first statement is true. Now let's see why the other statements are not true. Here, the number of protons must equal the number of neutrons within the atom. Alright. So if we look up above, we said that we had 5 of these protons within the nucleus, and we had 6 of these neutrons within the nucleus. In this example of the atom, we can clearly see that the number of protons and neutrons are not equal. Now there are gonna be times when a certain atom may have the same number of protons and neutrons, but that's not always a given. So this statement is not always true. The atom is best described as a uniform sphere of mass in which electrons are embedded. Alright. So if we look at the atom itself, first of all, I said that the nucleus, I blew it up to show what's within it. But in reality, the nucleus is extremely small when it comes to the atom. Okay? It's very, very small in relation to the whole volume of the atom. We're also going to say here that the word uniform is what gives this away as being long. The atom isn't uniform. It's not the same throughout. There's a part of the atom, that's the nucleus, which is different from other parts of the atom which are not the nucleus. Within the atom we have swirling around the nucleus these electrons. Okay. So the composition is not exactly the same everywhere. There's unique parts to the atom in different places. So this would mean that it's not a uniform sphere of matter, it has different parts to it. The volume of the nucleus is very large fraction of the total volume of the atom. So this is saying the exact opposite of what I said. The nucleus itself is extremely small. In the image above, I've blown it up to show it better, to show that within the nucleus are housed are protons and neutrons. In reality, it'd be super super small and hard to see all these protons and neutrons. So this is false. It's very small fraction of the total volume of the atom. Now that we've done this example question, let's continue onward with our discussion of the nucleus of the atom.
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concept
The Atom
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So we've talked about the nucleus. It's at the very center of the atom. It's extremely small in relation to the total volume of the atom, and it contains protons and neutrons. Now when it comes to our nucleus, there are forces at work that help to keep that nucleus together, but there's also forces at work that try to pull it apart. Now we're gonna say within the nucleus, there are these 2 major forces that characterize the behavior between protons and neutrons. Now we have what's called our nuclear force, the force within the nucleus that pulls together protons and neutrons. The way we have to think about it is, in chemistry we say that opposites attract. If you have opposite charges, you attract one another. Same charges repel one another. If you think about it, you have positively charged protons around. If you get them close enough to each other, because they have the same charge, they're gonna wanna repel each other. The way we prevent this from happening is the neutrons. The neutrons have no charge for a reason. They kinda act as the glue that keeps the nucleus together. K. We'll go into greater detail several chapters from now when we cover nuclear chemistry and talk more in-depth about nuclear force and electro static force, but just realize here that the neutrons kinda act as the glue that keeps together the protons, which have the same charge. All these protons with positive charges don't wanna be next to each other. Now besides the nuclear force, we have the electrostatic force. The electrostatic force is the force within the nucleus that pulls apart protons and neutrons. So it's just basically this balancing act between the two forces. If nuclear force is greater than electrostatic force, it has an effect on the nucleus. If electrostatic force is greater than nuclear force, it has an effect on the nucleus. Now we're gonna say for a stable nucleus that is held together. Remember the force that's holding it together is the nuclear force. It keeps them it keeps everything together. The electrostatic force is what's trying to pull things apart. If you wanna have a stable nucleus that is together, you wanna make sure that your nuclear force is greater greater than your electrostatic force. So just realize again the 4 primary parts of the atom, and realize that within the nucleus it's not a done deal that it's going to hold together and your atom will exist. You have these two forces that are at kind of like odds with one another, And if one is greater than the other, it can either mean the nucleus is held together or it's broken down and totally destroyed. Now that we've understood the basic parts of the atom, now that we've discussed the nucleus, let's continue on to our next question.
Within the nucleus, the nuclear force keeps it together and the electrostatic force pulls it apart.
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example
The Atom Example 2
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So if we take a look at this example question, it says, which of the following statements is false? So we're looking to see what is not true. A. The nucleus is composed of protons and neutrons. Well, we know that's true, we've talked about that in the very beginning. The nucleus has protons and neutrons, and spinning around the nucleus are the electrons. So this is true. When the nuclear force is less than the electrostatic force, then the nucleus will not remain intact. Alright. So let's go up above. We said that the nuclear force holds it together, the electrostatic force tries to pull it apart. We said that the nucleus will be held together as long as the nuclear force is greater than the electrostatic force. But what happens if that's not true? Well, if your nuclear force is less than your electrostatic force, it makes sense that the nucleus would not be held together. So this is also true. Right? Because we're saying the opposite of what we said up here. The nucleus has an overall neutral charge. Well, the nucleus houses what? Positive protons and neutral neutrons. So I'm just doing shorthand, proton p, it has a positive charge. Neutrons n has no charge. Usually, we denote that with a 0 or circle here to show that it has no charge. Think about it. We have positive charges only within the nucleus. There's no other charges within it. So the nucleus overall should have a positive charge, not a neutral charge. So this is false. And then d, when the nuclear force is greater than the electrostatic force, then the nucleus will remain intact. Well, that's exactly what we said up above. If your nuclear force is greater than your electrostatic force, then the nucleus is stable and will be held together. So just remember, when it comes to the nucleus, we have these two forces that are opposing one another trying to, be the primary force, and this can either lead to the stability of the nucleus or have it fall apart.