2. Atoms and the Periodic Table
Ions and the Octet Rule (Simplified)
The Octet Rule states that main-group elements will generally form enough bonds to obtain 8 electrons in their valence shell.
The Octet Rule
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concept
Ions and the Octet Rule (Simplified) Concept 1
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there's a tendency of main group elements and achieving eight valence electrons or filled outer shell but undergoing chemical reactions, Main group metals lose electrons to be like the noble gas that is before them. In the periodic table for instance, let's say you're dealing with sodium, Which has an atomic number of 11. The noble gas before it is neon, Which has an atomic number of 10. sodium wants to lose one electron to become just like Neon. Now, non metals tend to gain electrons to be like the noble gases that is after them in the periodic table. So if we look at chlorine for example, Chlorine has an atomic number up 17. It would need to gain one more electron to be just like the next noble gas, which would be are gone. Yeah, So that's how non metals and metals relate to the noble gases. Now, why do they do this? They do this to create totally filled energy levels which leads to greater stability and lower chemical reactivity. If we take a look here at this image, we have lithium and we have foreign lithium has one valence electron here on the outside valence electron is just its outer shell electron Flooring has seven outside electrons Or outer shell electrons. Their electron arrangements are 2-1 for lithium because it only has one on it. In its second shell and foreign is 2-7. lithium is a group one and they want to lose one electron to become plus one, Losing what electron now makes lithium plus one. And now it has a filled outer shell. Remember the first shell can hold a maximum of two electrons? Where did the electron go? Well, the electron isn't lost entirely. It got transferred over to flooring. So here it is. Right here by accepting that one electron flooring now has a failed outer shell. It has eight. And they do this again to be like the noble gases by losing one electron lithia. L. I. Plus now has a similar electron arrangement to helium and by gaining one electron Floren or fluoride, in this case has a similar electron arrangement to neon. So when it comes to these different types of ions in the octet rule, just remember they're either gaining or losing electrons to be like the nearest noble gas.
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example
Ions and the Octet Rule (Simplified) Example 1
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Here, it says, how many electrons must the sodium adam lose in order to obtain a filled outer shell? So look at the periodic table. sodium has an atomic number of 11, which we're told right here. Remember metals tend to lose electrons to be like the noble gases that came before them. So what's the noble gas before sodium? If you look, it would be neon. So we want to go from 11 electrons to 10 electrons. So so do you would have to lose one electron? So here, the answer would have to be option A.
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Ions and the Octet Rule (Simplified) Example 2
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All right. So, we're going to stay here with a metal cat eye on remember cat ions are positive ions. We first remove electrons from the highest energy level. So here it says, right, the electron arrangement for the following ion, we have calcium ion CA two plus. It has an atomic number of 20. All right. So the steps that we need to take, we're gonna say we're going to provide the electron arrangement for the neutral form of the element. So calcium neutral has 20 electrons. So, remember, it would have to in the first shell, eight in the second shell, eight in the second shell and two in the fourth shell. If you don't remember how to do this, remember to go back to my videos on electron arrangements Now two plus would mean what we've lost two electrons. So that leads us to step to begin removing electronic electrons from the highest energy level. To obtain a desire charge. Recall each electron remove caused the ion charge to increase by plus one. So we're gonna lose two electrons. Remember this is the first show second shell, third shell, fourth shell or fourth energy level. This is the highest energy level. So we're gonna lose two electrons. It has to come from there. So here, the calcium ion, which is simply be 2-8-8. This would be electron arrangement of the calcium ion.
For a metal cation, first remove electrons from the highest energy level.
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Ions and the Octet Rule (Simplified) Example 3
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with a non metal and ion add an electron or electrons to the orbital's with available space. All right. So, we're gonna write the electron arrangement for the following ion are dealing with the nitride ion that's N three minus. Nitrogen has an atomic number of seven. So, let's follow the rules here. Here's step one would provide the electron arrangement for the neutral form of the element nitrogen is neutral here. The first shell can hold a maximum of two electrons but we need to get to seven electrons based on its atomic number. So that would mean the second shell would have to have five electrons. So this represents the electron arrangement of the neutral nitrogen atom. But what about N 3 -? What does the -3 mean? Well, here's step two says you add electron city energy level that can accommodate more electrons minus three year means you've gained three electrons. So you have to add three electrons. The first shot can only hold a maximum of two electrons. So it's full. It can accommodate anymore. The second shell, though, can hold up to eight electrons. And guess what if it can hold up to eight? We can add the three additional electrons we gained to that second shell, So the nitrate ion would be 2-8 for its electron arrangement.
For a non-metal anion, add electrons to the orbital with available space.
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Problem
ProblemDetermine the electron arrangement for the Cl– ion.
A
2-8-7
B
2-8-8
C
2-8-6
D
2-2-6-2-6
E
2-2-6-2-5
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Problem
ProblemDetermine the electron arrangement for the Al3+ ion.
A
2-8-3
B
2-8-6
C
2-8
D
2-2-6
E
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