How many electron dots should appear in the Lewis structure for each of the following molecules

How many electron dots should appear in the Lewis structure...

Key Concepts

Lewis Structure

The Lewis structure is a diagram that represents the arrangement of valence electrons among atoms in a molecule or ion. It shows both bonding electrons (shared between atoms) and lone pairs (non-bonding electrons), providing insight into the molecule’s connectivity and overall stability.

Valence Electrons

Valence electrons are the electrons located in the outermost energy level of an atom. These electrons are involved in chemical bonding and are represented as dots in the Lewis structure. Accurately counting the total number of valence electrons, including adjustments for ions, is essential for drawing a correct electron dot diagram.

Electron Dot Notation

Electron dot notation is a method of depicting the valence electrons of an atom using dots placed around its elemental symbol. This notation is fundamental in constructing Lewis structures because it helps visualize both bonding electrons and lone pairs for determining molecular properties.

Octet Rule

The octet rule is a guideline stating that atoms tend to bond in such a way that they each end up with eight electrons in their valence shell, mimicking the electronic configuration of noble gases. This rule is crucial when assigning electrons in Lewis structures, ensuring that atoms reach a stable electronic configuration whenever possible.

Polyatomic Ions

Polyatomic ions are charged species composed of two or more atoms covalently bonded together, with an overall net charge. When drawing their Lewis structures, it is important to account not only for the total number of valence electrons from each constituent atom but also for the extra electrons that contribute to the ion’s charge. This ensures an accurate depiction of the electron distribution within the ion.

Transcript

00:01 So for this question, we're given several different molecules, and we're asked to draw lewis structures for each of them.

00:08 So let's start with a, where we have of2.

00:14 So first, we're going to find the total number of valance electrons for the molecule.

00:19 So we add up the valence electrons for each atom.

00:22 So oxygen contributes six valence electrons, which you can just get this information from the periodic table.

00:31 And fluorine contributes seven valence electrons, and there's two fluorines.

00:38 So two times seven, we have 14 valence electrons.

00:43 So this molecule is contributing a total of 20 valence electrons that we're going to incorporate into the structure.

00:51 So next we'll write our skeleton structure.

00:55 Our central atom is going to be oxygen.

00:58 It's the most unique, and it is the least electronegative.

01:03 And then we will show it bonding to fluorine on each side.

01:09 So the two bonds is four total electrons.

01:14 So we'll take four minus our 20 total electrons, which leaves us with 16 electrons that we are going to fill in as loan pairs.

01:26 So we're first filling those lone pairs on the terminal atoms, which are fluorine.

01:32 So we have one, one, two, three, four, 5, 6, 7, 8, 9, 10, 11, 12.

01:45 We still have four more to add, so then we'll add those to our central atom, which is oxygen.

01:52 13, 14, 15, 16.

01:55 So we have our 20 valence electrons in the molecule.

02:01 And then we also, each atom has the octet rule satisfied.

02:07 So each atom has eight electrons around it.

02:12 So we know that this will be the correct lewis structure for that particular molecule.

02:20 Next, we'll go to b with n2f2.

02:24 So nitrogen has five valence electrons.

02:27 There's two nitrogen.

02:29 So that's going to contribute 10 valence electrons.

02:32 Fluorine, just like before, contribute seven.

02:35 There's two fluorines.

02:36 So that's going to contribute 14 total balance electrons.

02:40 So in the molecule, we're going to have a total of 24 valence electrons.

02:48 So next, we'll write our skeleton structure.

02:52 Nitrogen is less electronegative than fluorine.

02:57 So nitrogen is going to be our central atom.

03:04 And then f will be our fluorine will be our terminal atom.

03:12 So we have one, two, three bonds, which is six electrons.

03:18 So 24 minus 6 means that we have 18 electrons to start filling in.

03:26 So we'll start filling them as lone pairs to our terminal electrons.

03:32 So we have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12.

03:41 So we still have 6 more electrons that we need to fill in.

03:50 So of those six, we can say one, two, three, four.

03:55 We'll fill in as lone pairs to our central atoms.

03:58 Now, we still have two more electrons that we need in order to reach this 24 electron number.

04:05 However, to have each atom fulfill the octet rule, nitrogen, the two nitrogens each need two electrons.

04:18 So, with those two electrons, we need to add, if we, write it as a bond, a double bond between the two nitrogens.

04:31 We will have a total of 24 electrons, and each atom fulfills the octet rule.

04:38 They have eight electrons.

04:42 So this will be our final lewis structure for the molecule.

04:47 We'll go to c next.

04:50 So let's find the total valence electrons for the molecule.

04:54 Silicon has four valence electrons.

04:58 So since we have two silicon atoms, we have eight total electrons, hydrogen contributes one valence electron, but there's six of them.

05:08 So we have six valence electrons, or a total of 14 valence electrons for the molecule.

05:18 So let's start our skeleton structure.

05:21 Hydrogen can never be the central atom because it's a total.

05:25 Because it can only have a total of two valence electrons.

05:29 So silicon is going to be our central atom.

05:33 And then the hydrogens are going to be our terminal atoms.

05:38 So we will do three hydrogens for each silicon.

05:49 And then we'll count our bonds to see how many electrons we have.

05:54 One, two, three, four, five, six, seven bonds.

05:57 Two electrons per bond.

05:59 Seven times two is 14.

06:01 So we've already reached our 14 valance electrons for the molecule, and each atom has its octet rule satisfied.

06:11 Both silicon atoms have eight electrons around them, and each hydrogen has two valance electrons.

06:18 So we don't have to add any lone pairs, and this will be our finest lewis structure for the molecule...

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