In which of the following does the central atom obey the octet rule: NO2, SF4, NH3, SO3, O2^- ?

step 1 In this question, we're going to be looking at the octet rule. We have a number of atoms or mole

In which of the following does the central atom obey the...

Key Concepts

Odd-Electron Species

Odd-electron species are molecules or ions that contain an unpaired electron, resulting from having an odd total number of electrons. This unpaired electron often imparts significant reactivity, characterizing these species as free radicals, and affects their bonding and overall stability.

Electron Counting

Electron counting involves determining the total number of valence electrons available in a molecule or ion, which is essential for drawing Lewis structures and checking whether atoms fulfill the octet rule. This technique helps in understanding the distribution of electrons and identifying anomalies like odd-electron species.

Expanded Octet

Expanded octet refers to the ability of atoms, typically those in the third period and beyond, to accommodate more than eight electrons in their valence shell due to the availability of d-orbitals. This concept explains how certain molecules can have central atoms with more than eight electrons and still be stable.

Octet Rule

The octet rule states that atoms tend to form bonds in such a way that each atom has eight electrons in its valence shell, mimicking the electron configuration of noble gases. This principle is a guideline for predicting the structure of many stable molecules, especially for main-group elements in the second period.

Transcript

00:01 In this question, we're going to be looking at the octet rule.

00:04 We have a number of atoms or molecules that we're going to draw, and let's get started.

00:10 So the first one is nitrogen and two oxygens, so n -o -2.

00:15 We'll start with drawing the nitrogen in the center.

00:18 We will double bond it to an oxygen, and we will single bond it to the other oxygen.

00:25 And we'll dot in some electrons.

00:30 And let's check our valence structure to make sure that it has the right number of electrons.

00:38 So we have five electrons for the nitrogen, six for each of the oxygens.

00:44 So we should expect a total of 17 valence electrons.

00:48 We have eight over here.

00:50 We have eight over here.

00:52 16 and then we have one more, make 17.

00:57 So one thing to note is that this nitrogen has access to seven electrons and normally we would expect eight.

01:10 So in this case the nitrogen is not satisfying the octet rule.

01:20 Okay, our next compound is sf4.

01:31 So we have six electrons for the sulfur, seven for each of the fluorines, and there's four fluorines.

01:41 So that's 6 plus 28, and that should be 34 electrons.

01:47 I'll put sulfur in the center.

01:50 We'll bond it to the four fluorines, and we'll give the sulfur -free pair.

02:03 And each fluorine, of course, gets six free electrons, or six unbonded electrons.

02:12 And let's add them up.

02:14 So we have 8 over here, 8 over here.

02:20 4 groups of 8, that's 32, and then plus this lone pair makes 34.

02:28 Now, let's look at this sulfur.

02:31 This sulfur has 8 electrons and bonds, and then it's got 2 as free electrons.

02:39 So that's a total of 10 electrons.

02:41 This violates the octet rule, but that's okay because sulfur is in row 3 or higher on the periodic table.

02:50 Remember that elements in row 3 or higher have access to a d orbital where they can store extra electrons.

02:58 So they aren't confined to having eight electrons per atom.

03:04 Okay.

03:07 Next, we have nh3.

03:12 So nh3.

03:17 So that's going to look like this.

03:28 And let's just double check.

03:30 We have five plus three, eight electrons.

03:34 Total.

03:37 We have three bonds, so that's six electrons, and then a free pair, so that's eight.

03:44 And if we look at this nitrogen, this nitrogen has eight electrons...

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