Lewis Dot Symbols - Video Tutorials & Practice Problems
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Lewis Dot Symbols represent the outer shell electrons of an element.
Lewis Dot Symbols
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Lewis Dot Symbols
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Now Lewis dot symbols, sometimes referred to as electron dot diagrams, are diagrams that represent the valence electrons of an atom or ion. Now when we talk about valence electrons, we look at it in terms of main group elements versus transition metals. Now for main group elements, the group elements that are groups 1 a to 8 a, the number of valence electrons that they possess is equal to their group number. So for example, if we're looking at aluminum, aluminum is in group 3 a, so it would have 3 valence electrons. For transition metals, it's a bit different. For them, it's the number of valence electrons equals their s+d electrons. So just remember when we're looking at an element and trying to determine its number of valence electrons, you first have to look at it as being either a main group element or a transition metal.
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example
Lewis Dot Symbols Example 1
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Here it states which element will possess the most valence electrons. Now one of them I already gave away. Remember, aluminum is in group 3 a, so it has 3 valence electrons. Now if we look, we have sulfur, calcium, hydrogen, and bromine. None of them are transition metals, so we don't have to worry about the number of s or d electrons that they possess. They're all main group elements, so look on your periodic table and see what group do they belong to. Sulfur is in group 6 a, so it has 6 valence. Calcium is in group 2 a, so it has 2 valence electrons. Hydrogen is in group 1 a, so it has 1 valence electrons. And then finally, bromine is in group 7 a, so it has 7 valence electrons. So we'd see that bromine is the one that has the most valence electrons at 7.
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Lewis Dot Symbols
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So let's take a look at the rules for drawing a lewis dot symbol. First thing we need to realize is that we have our element symbol. So here hydrogen is h, aluminum is a l, and then we have our surrounding dots in red. Now we're gonna see there are some exceptions to this, but a vast majority of these surrounding dots are red. What we need to realize here is that when we're talking about our element symbol, it represents that element's nucleus as well as its core electrons and we'll say those core electrons are green. The surrounding dots represent the valence electrons for that particular element. Now if we take a look, we see that lithium is in group 1 a. Since it's a main group element it has one valence electron which is represented by this one dot. If we look at carbon, carbon is the main group element. It's in group 4 a, so it has 4 dots around it. Now, the way we tend to do it is we add our first dot here at the top and as we add more and more dots we start adding them clockwise. So here goes one for beryllium, boron has 3, so we add 1 here, and carbon has 4, so we add another one here. When we get to nitrogen, now we start pairing them up. And that's how we draw our Lewis dot electrons. Now if we take a look at hydrogen and helium, their electrons are green, which means that they represent their core electrons. Remember, hydrogen and helium only have one electron shell. Because they have that one electron shell, you could say it represents their core electrons or even their valence electrons. Okay? So they're a little bit of an exception to what we're accustomed to seeing. If we take a look at our transition metals, remember we said for transition metals, we look at their s and d electrons to determine the number of valence electrons. Configuration is argon 4s23d2. It would have 4 valence electrons total from adding the s and d electrons. Now, you need to remember the rules that we went over in terms of electron configurations to know what I'm talking about. If you haven't, I highly suggest you go back and take a look at electron configurations. If we look at, if we look at Manganese, Manganese would be argon 4 s 2 3 d 5. So that would be 7 valence electrons. But Jules, what if I don't wanna do the electron configuration? Well, you don't necessarily have to because here's a trick. The number of valence electrons for these transition metals, you can determine them by looking at their group number. So 3 b is group 3, group 1b is group 11. These numbers here also correspond to the number of valence electrons each of the transition metals have. So if you don't wanna waste your time in writing out the electron configuration of, let's say, for example, zinc, zinc is in group 12, which also equals the number of valence electrons. Because if we look, we have 2 s electrons plus 10 d electrons, which adds up to 12. So just remember these little key things when it comes to the electron, dot symbols for each one of these elements from the periodic tape.
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example
Lewis Dot Symbols Example 2
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1m
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Here we're told to draw the Lewis dot symbol for the following element, tellurium. Now step 0 tells us to identify if the element is a main group element or a transition metal. Step 1 tells us to place 1 valence electron at a time on the four sides of the element, and we're gonna start from the top of the element and move clockwise. Tellurium since it's in group 6 a has 6 valence electrons. We're gonna have the first one here. Step 2 tells me to continue adding electrons pairing them up until you have reached the appropriate number of valence electrons. So 1, 2, 3, 4. I still have 2 more to draw, so keep going clockwise. 5, 6. Step 3 tells me if you are given an ion, place it in brackets and put its charge in the upper right corner. Remember, a cation is a positive ion. We get those by removing electrons, so we'd have to start removing these valence electrons. For an anion which is a negative ion, you would be gaining electrons so you'd be adding those electrons. Here tellurium is not an ion and has no visible charge, no positive or negative charge present. So this would simply be our answer here. It would just be tellurium with our 6 dots.
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Problem
Problem
Draw the Lewis Dot symbol for the following ion:Co+
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Problem
Draw the Lewis Dot symbol for the following ion: Cd2+
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Problem
Draw the electron-dot symbol for the following ion:P3–
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