Lewis Dot Symbols (Simplified) - Online Tutor, Practice Problems & Exam Prep

Lewis Dot Symbols (Simplified) Concept 1

Now, Lewis dot symbols, sometimes referred to as electron dot diagrams, are diagrams that represent the valence electrons of an atom or ion. When we talk about valence electrons, we look at it in terms of main group elements versus transition metals. For main group elements, the group elements that are groups 1A to 8A, 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 3A, so it would have 3 valence electrons. For transition metals, it's a bit different. For them, 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.

Lewis Dot Symbols (Simplified) Example 1

Here it states which element will possess the most valence electrons. Now one of them I already gave away. Remember, aluminum is in group 3A, 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 they belong to. Sulfur is in group 6A, so it has 6 valence electrons. Calcium is in group 2A, so it has 2 valence electrons. Hydrogen is in group 1A, so it has 1 valence electron. And then finally, bromine is in group 7A, so it has 7 valence electrons. So we'd see that bromine is the one that has the most valence electrons at 7.

Lewis Dot Symbols (Simplified) Concept 2

Now when it comes to drawing a Lewis dot symbol, it's important to understand what is meant by element symbol versus the surrounding dots. When we say element symbol, that equals the nucleus of the element as well as its core electrons. When we say the surrounding dots, these equal the element's valence electrons. Now hydrogen is a little bit weird and so is helium. Both have only one shell, so their valence electrons can also be interpreted as their core electrons, because that's their total number of electrons. Now for the other elements after them though, what we see in red represents the valence electron for that particular element. Now remember, for main group elements, the number of valence electrons V=G, where V is the number of valence electrons and G is the group number. So, you can see that lithium, sodium, and potassium, which are all in group 1a, have one dot. And you can see that the elements in group 6a, oxygen, sulfur, selenium, as well as the ones below them, they all have 6 dots. Now, as always, transition metals are a little bit different. They can have unexpected situations, so we tend to avoid Lewis dot symbols for transition metals. We're going to focus on main group elements. So remember, for a main group element, the number of valence electrons is equal to their group number.

Lewis Dot Symbols (Simplified) Example 2

Here it says to draw the Lewis dot symbol for the following element. Here we're dealing with Tellurium. So let's follow the steps. Step 0 says, first, we need to identify the group number of the main group element. Here, Tellurium itself is in group 6a. Next, we're going to ignore transition metals because their electron arrangement causes unpredictable patterns. So don't worry about the transition metals like I said before. Step 1, you're going to place 1 valence electron at a time on the four sides of the element. Start from the top of the element and move clockwise. So we're going to have tellurium, and it's in group 6a, so that means it has 6 valence electrons. So we're going to start off with 1, 2, 3, 4. Remember, we have to get to 6, so we're still missing 2 more. 5, 6. We followed step 2, where it says continue adding electrons, pairing them up until you reach the appropriate number of valence electrons. Here we need to get to 6 valence electrons, which is what we just did. So this here represents the Lewis dot symbol for tellurium.

Draw the Lewis Dot symbol for the following element:Sr

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Draw the Lewis Dot symbol for the following element:Pb

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Draw the electron-dot symbol for the following element:Rn

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