One scale for electronegativity is based on the concept that...

One scale for electronegativity is based on the concept that the electronegativity of any atom is proportional to the ionization energy of the atom minus its electron affinity: electronegativity $=k(\mathrm{IE}-\mathrm{EA})$, where $k$ is a proportionality constant. (a) How does this definition explain why the electronegativity of $\mathrm{F}$ is greater than that of $C l$ even though $C l$ has the greater electron affinity? (b) Why are both ionization energy and electron affinity relevant to the notion of electronegativity? (c) By using data in Chapter 7 , determine the value of $k$ that would lead to an electronegativity of $4.0$ for $\mathrm{F}$ under this definition. (d) Use your result from part (c) to determine the electronegativities of $\mathrm{Cl}$ and $\mathrm{O}$ using this scale. Do these values follow the trend shown in Figure 8.6?

Key Concepts

Electronegativity

Electronegativity is a measure of an atom's ability to attract electrons toward itself in a chemical bond. It is a key concept in chemistry that helps explain the nature of chemical bonds, the transfer or sharing of electrons, and the resulting molecular polarity. Understanding electronegativity is central to predicting bond types and reactivity patterns in compounds.

Ionization Energy

Ionization energy is the energy required to remove an electron from an atom or ion in the gaseous state. It is a fundamental property of atoms that reflects the strength of the attraction between the nucleus and its electrons. High ionization energies indicate a strong attraction, which is an important factor when considering how readily an atom may attract electrons in a bonding situation.

Electron Affinity

Electron affinity measures the energy change when an electron is added to a neutral atom in the gaseous phase. It provides insight into an atom's tendency to accept electrons. The concept is closely related to electronegativity because the more energy that is released upon electron gain, the more strongly the atom attracts electrons.

Proportionality Relationship in Electronegativity Scales

Several electronegativity scales use proportional relationships that combine ionization energy and electron affinity to quantify an atom's electron-attracting ability. In such scales, a constant factor is used to scale the difference between the ionization energy and electron affinity, thereby correlating this difference to electronegativity. This approach underscores why both properties are essential for understanding electron attraction in atoms.

Periodic Trends in Electronegativity

Periodic trends in electronegativity arise from systematic variations in atomic properties such as ionization energy and electron affinity across the periodic table. Elements in the same period or group typically show predictable changes in electronegativity, which can be rationalized by how their atomic sizes, nuclear charges, and electron shielding effects influence the ability of an atom to attract electrons.

Transcript

00:01 This problem had a lot of writing on it, but it wasn't that hard to do.

00:06 We're given the following information.

00:09 One scale for electron negativity is based on the concept that the electronegativity of any atom is proportional to the ionization of the atom minus its electron affinity.

01:42 The equation for this is the electronegativity is equal to proportionality constant k times the ionization energy minus the electron affinity.

02:03 Okay, that's the information that we're given.

02:10 Part a says how does this definition explain why fluorine has a greater electron negativity than chlorine, even though chlorine has greater electron affinity? okay, so we're going to figure out, we're going to have to have definitions in mind in order to do this.

03:55 Let's see here.

03:57 Okay, f is above, immediately above.

04:03 Cl in the periodic table, which means that cl is larger because it's got more energy levels, greater shielding.

04:21 F is smaller, which means electrons are more tightly bound to nucleus.

04:40 I should have gone to the other page.

04:46 So it has a greater ionization energy.

04:56 I'm just going to abbreviate that i.

04:57 That's ionization energy.

05:04 And it has a smaller electron affinity.

05:18 See if i got over here.

05:19 Atomic radius is smaller for fluorine.

05:30 Chlorine has a smaller ionization energy and a greater electron affinity.

05:45 Now according to our definition, we said that the concept for electronegativity is this is the proportional to the ionization energy minus the electron affinity.

06:01 So our answer for part a continued is that the difference between the ionization energy and electron affinity is very nice there is greater for fluorine than it is for chlorine.

07:01 Therefore, fluorine has the greater electronegativity.

07:24 Okay, i think that's everything we have to do.

07:27 I probably overkill that a bit.

07:31 That's okay.

07:34 B, why are both ionization energy and electron affinity relevant to the notion of electronegativity? which i will call i from now on, which i will call ea from now on.

08:16 Relevant.

08:33 So in order to do this, let's make sure we understand all of the definitions.

08:39 Electronigativity measures the ability of an atom to attract electrons to itself in a compound.

09:28 Causing different charges of the atoms in that compound.

09:34 Ionization energy measures the energy required.

09:44 I'm going to also make a note back up here that this is generally a relative scale.

09:53 It can be a relative scale.

09:57 Ionization energy measures the energy, and it actually measures the energy, required to remove an electron from a gaseous atom or ion.

10:21 So low ionization energy, easy to remove.

10:35 High ionization energy, difficult to remove.

10:41 And electron affinity.

10:46 That measures the energy change when a gaseous atom or ion gains an electron.

11:22 So a higher electron affinity means that electrons are more easily accepted.

11:32 Okay, now since the electronegativity in compounds can involve, the loss and gain of electrons by atoms, both ionization energy and electron affinity are relevant.

12:41 Okay, that should be it.

12:43 It's probably more than enough for part b.

12:46 Part c.

12:50 Oh, let's use this funny color.

12:54 By using the data in chapter 7, so you have to go back to chapter 7, find the value for a proportionality content.

13:07 Proportionality constant that would lead to an electronegativity of 4 for f.

13:20 I sort of abbreviated that, but that's pretty easy.

13:24 So this involved looking up a few numbers, which wasn't too difficult.

13:29 I'm going to start by writing the equation down again.

13:35 Electronigativity is equal to the proportionality constant times the ionization energy minus the electron affinity.

13:50 And looking up in the tables for fluorine, i was 1 ,681 kilojoules per mole, and our electron affinity was negative 328 kilojoules per mole...

Please give Ace some feedback