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GOB Chemistry

Learn the toughest concepts covered in your GOB - General, Organic, and Biological Chemistry class with step-by-step video tutorials and practice problems.

Table of contents
Atoms and the Periodic Table

Electron Arrangements

Electron Arrangement gives the number of electrons in each energy level (n).


Electron Arrangements Concept 1

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the electron arrangement of an atom gives a number of electrons in each energy level. Now recall as the value of an increases than both. The size and energy level of an atomic orbital will also increase. And we're going to say, as we increase the energy levels, the number of electrons within a given orbital will also increase. So for example, if we have electrons in shells two and 55 is a higher energy levels, so we expected to have more electrons than an energy level of two. Now the energy level shell numbers of an atom can be tied to the period or rows of the periodic table. So these are things that we've examined before when it comes to the atom itself. But now we're going to apply them to electronic arrangements. So now click on the next video and let's take a look at an example question.

Electron Arrangements Example 1

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So here we have to complete the electron arrangements for the following elements of the periodic table. All right. So, we're gonna start out with hydrogen, which has an atomic number of one, which means it has only one electron. So its electron arrangement is simply just one helium is too Because it has to um electrons because its atomic number is two. All right. So now what's going to start happening is we're gonna start adding more and more electrons. Remember, in the first shell we can hold a maximum of two electrons. And that's because two times and squared in the second shell, we can theoretically hold up to eight electrons. So now we're at lithium, lithium has an atomic number of three. The first two electrons are in the first. Shut this space here. So now we're talking about electrons in the second shuttle dash. How many is that one? And it's one because again, it's total atomic numbers three, which means it has in total three electrons. We've accounted for the first two in the first show. And then this third one is in the second show. Then we move over, we go from lithium. Then beryllium beryllium will be 2-2. Now let's go to bore on here. So bore on here would be to three. Right? Because its atomic number is five. So, it can have five total electrons to are in the first shell because the first shell can only hold a maximum of two. The remaining three that we need are in the second show. Then we have carbon, nitrogen oxygen. Let's look at flooring here, Florida atomic number is nine. That means it has nine total electrons. Two of them are in the first shell, and then the other seven are in the second show. Let's keep going. All right. So, for sodium, sodium has an atomic number of 11 on the periodic table. The first two are in the first show. The next eight are in the second show, we need one more electron and it will be here in the third show. Let's keep going skip over to aluminum. Aluminum has an atomic number of 13. So, we have two electrons in the first eight electrons in the second shot. And three in the third show. All right. When it comes to depicting the number of electrons in each of these shells were going to say that the second show Can have up to eight. And when we're doing electron arrangements were going to say yes, theoretically that the third shot can hold up to 18 electrons. But here in purposes of an electron arrangement, we're gonna say we go up to eight. So, potassium has an atomic number of 19. So, it has two electrons in the first shell eight in the second eight and the third. And we need one more to get to 19. So it has one. Okay, In the 4th Shell. So here we have our electron arrangement of different elements on the periodic table. And what's important to know is that electron arrangements are simple as long as we keep them that way. We're gonna say here that elements beyond An atomic number of 20 can have partially filled orbital's and are beyond the scope of this course. So really only need to know up to calcium all the remaining elements you don't need to worry about. All right. So keep this in mind when it comes to electron arrangements. The maximum we can hold in the first shell is too. And the third in the second shot eight in the third, shelf eight. And in the fourth shell too, those are the maximum numbers that we can have electrons in each one of those four shells

Write the electron arrangement for the following element:Calcium (Z = 20)