Predicting bond type (electronegativity) | Types of chemical bonds | AP Chemistry | Khan Academy

Summary

This video script discusses the spectrum of chemical bonding, emphasizing that bonds are not strictly ionic, covalent, or metallic but can vary in nature. It explains how electronegativity differences influence bond polarity, using the example of a polar covalent bond between oxygen and hydrogen. The script also touches on metallic bonds, which form when two low electronegativity elements share electrons in a communal pool, leading to properties like conductivity.

Takeaways

• 🔬 Bonding between atoms can be categorized as metallic, covalent, or ionic, depending on the elements involved.
• 🌟 The nature of bonds is a spectrum, with polar covalent bonds exhibiting characteristics between nonpolar covalent and ionic bonds.
• 📊 Electronegativity is a key factor in determining the type of bond formed, representing an atom's ability to attract electrons.
• 📉 A low difference in electronegativity between atoms leads to nonpolar covalent or metallic bonds.
• 📈 A high difference in electronegativity results in polar covalent or ionic bonds, with the more electronegative atom attracting the electrons more.
• 🧲 Electronegativity increases from the bottom left to the top right on the periodic table.
• 🔋 Metallic bonds typically form between elements with similar and relatively low electronegativities, facilitating the sharing of electrons.
• 💧 In a polar covalent bond, such as between oxygen and hydrogen, there is an unequal sharing of electrons, leading to partial charges on each atom.
• 🌐 The Pauling scale is used to measure electronegativity, with oxygen being one of the most electronegative elements.
• 🔄 Electrons in a polar covalent bond spend more time around the more electronegative atom, creating a dipole.

Q & A

What are the three main types of bonds that can form between atoms?

The three main types of bonds are metallic bonds, covalent bonds, and ionic bonds. Metallic bonds typically form between two metals, covalent bonds form between two nonmetals, and ionic bonds form between a metal and a nonmetal.

What is the significance of electronegativity in determining the type of bond formed?

Electronegativity is a measure of an atom's ability to attract electrons in a bond. It plays a crucial role in determining the polarity of a bond. A large difference in electronegativity between two atoms typically results in an ionic bond, while a small difference leads to a covalent bond.

How does the concept of a bonding spectrum relate to electronegativity?

The bonding spectrum is a way to visualize the gradual transition from nonpolar covalent bonds to polar covalent bonds and eventually to ionic bonds based on the difference in electronegativity between the bonded atoms.

What is a polar covalent bond and how does it differ from a nonpolar covalent bond?

A polar covalent bond is a type of covalent bond where the electrons are shared unequally between the atoms due to a difference in electronegativity, resulting in a partial positive charge on one atom and a partial negative charge on the other. A nonpolar covalent bond occurs when the electrons are shared equally because the electronegativity of the atoms is similar.

What is the Pauling scale and how is it used to measure electronegativity?

The Pauling scale is a scale used to measure electronegativity, named after the chemist Linus Pauling. It assigns a number to each element that represents its ability to attract electrons in a chemical bond.

How does the electronegativity of oxygen compare to that of hydrogen?

Oxygen is more electronegative than hydrogen, with an electronegativity of 3.44 compared to hydrogen's 2.20 on the Pauling scale. This difference makes the bond between oxygen and hydrogen a polar covalent bond.

What is the general trend of electronegativity on the periodic table?

Electronegativity generally increases from the bottom left to the top right of the periodic table. Elements at the top right are more electronegative and tend to attract electrons more strongly.

What is the role of electronegativity in the formation of metallic bonds?

In metallic bonds, the atoms involved typically have similar and relatively low electronegativities, which makes them more willing to share their valence electrons in a communal pool, leading to properties like electrical conductivity.

How does the difference in electronegativity between two atoms affect the bond's polarity?

A greater difference in electronegativity between two atoms results in a more polar bond, where the electrons are more attracted to one atom, creating a partial negative charge on that atom and a partial positive charge on the other. Conversely, a smaller difference results in a less polar or nonpolar bond.

Can you provide an example of a bond that is intermediate between covalent and ionic?

Yes, a bond between oxygen and hydrogen is an example of an intermediate bond. Although both are nonmetals and would typically form a covalent bond, the significant difference in their electronegativities (oxygen being much more electronegative) results in a polar covalent bond that has characteristics of an ionic bond.

What property of metallic bonds allows for conductivity?

Metallic bonds involve a shared pool of valence electrons that are free to move throughout the metal lattice. This 'sea' of delocalized electrons is what allows metals to conduct electricity.

Outlines

00:00

🔬 Understanding Bond Types

This paragraph discusses the different types of bonds that can form between atoms, such as metallic bonds between two metals, covalent bonds between two nonmetals, and ionic bonds between a metal and a nonmetal. It introduces the concept of bonding as a spectrum rather than a strict classification. The video aims to explore this spectrum with a focus on electronegativity, which is the tendency of an atom to attract electrons in a bond. Electronegativity is described as a property that varies across the periodic table, with oxygen being notably high and hydrogen being lower on the scale. The paragraph also explains how the difference in electronegativity between two atoms can lead to polar covalent bonds, exemplified by the bond between oxygen and hydrogen, which results in a partial negative charge on oxygen and a partial positive charge on hydrogen.

Keywords

💡Bonding

Bonding refers to the process by which atoms of different elements combine to form compounds. In the video, bonding is discussed in the context of how atoms of the same or different elements interact to create metallic, covalent, or ionic bonds. The video emphasizes that bonding is not just a binary classification but exists on a spectrum, which is a key theme of the video.

💡Metallic Bond

A metallic bond is a type of chemical bond that involves a regular arrangement of cations that are in a 'sea' of delocalized electrons. It is highlighted in the script as a bond that typically forms between two metals or between atoms with similar and low electronegativity, which is essential for understanding why metals are good conductors of electricity.

💡Covalent Bond

A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. The video script describes how covalent bonds are likely to form between two nonmetals and are more common when there is a significant difference in electronegativity, such as in the case of oxygen and hydrogen.

💡Ionic Bond

An ionic bond is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions. The video explains that ionic bonds are likely to form between a metal and a nonmetal, particularly when there is a large difference in electronegativity, leading to one atom 'swiping' an electron from the other.

💡Electronegativity

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. It is a central concept in the video, used to explain the polarity of bonds and the nature of the bond (metallic, covalent, or ionic) that is likely to form between different types of atoms.

💡Polar Covalent Bond

A polar covalent bond is a type of covalent bond where the electrons are not shared equally, resulting in a molecule with partial positive and negative charges. The video uses the example of the bond between oxygen and hydrogen to illustrate how a significant difference in electronegativity can lead to a polar covalent bond.

💡Spectrum

The term 'spectrum' in the video refers to the range of possibilities between purely ionic and purely covalent bonds, emphasizing that bonding is not a binary concept but exists on a continuum. This spectrum is used to explain the varying degrees of electron sharing and attraction in different types of bonds.

💡Electron Sharing

Electron sharing is a concept that describes how atoms can share electrons to achieve a full valence shell. The video discusses how the degree of electron sharing varies, leading to different types of bonds, from fully shared in metallic bonds to unequally shared in polar covalent bonds.

💡Pauling Scale

The Pauling Scale is a measure of electronegativity named after chemist Linus Pauling. The video uses this scale to illustrate the electronegativity of different elements, such as oxygen and hydrogen, to explain the polarity of the O-H bond.

💡Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom and play a key role in chemical bonding. The video mentions valence electrons in the context of metallic bonding, where these electrons are shared in a 'communal pool', contributing to properties like electrical conductivity.

💡Conductivity

Conductivity in the context of the video refers to the ability of a material to conduct electricity. It is related to metallic bonds, where the sharing of valence electrons in a communal pool allows for the movement of electrons and thus conductivity.

Highlights

Types of bonds form between atoms of the same element: metallic bonds for metals, covalent bonds for nonmetals.

Ionic bonds likely to form between one metal and one nonmetal.

Bonding is a spectrum, not strictly categorized.

Polar covalent bonds can exhibit ionic characteristics.

Electronegativity is a key factor in determining bond type.

Electronegativity measures an atom's ability to attract electrons in a bond.

A low difference in electronegativity suggests a more ionic bond.

A high difference in electronegativity suggests a more covalent bond.

Electronegativity difference increases from left to right on the spectrum.

Oxygen and hydrogen bond example illustrating a polar covalent bond.

Electronegativity measured on the Pauling scale, with oxygen at 3.44 and hydrogen at 2.20.

Electronegativity trends from bottom left to top right on the periodic table.

Oxygen is one of the most electronegative elements.

In a polar covalent bond, electrons spend more time around the more electronegative atom.

Metallic bonds form when electronegativity differences are low and both atoms have low electronegativity.

Metallic bonds involve a shared pool of electrons, leading to properties like conductivity.

Transcripts

- In other videos, we had started talking

about the types of bonds that might form

between atoms of a given element.

For example, if you have two metals forming a bond,

well, you are going to have a metallic bond.

If you have two nonmetals,

engaged in some type of bonding activity,

this is likely to be a covalent bond.

And the general rule of thumb is

if you have one metal,

and one nonmetal,

that this is likely to be an ionic bond.

These are the general rules of thumb.

What I wanna do in this video is to better appreciate

that bonding is really more of a spectrum.

There are bonds,

and we've talked about things like polar covalent bonds,

that start to look a little bit more and more

ionic in nature.

And so that's what we're gonna talk about in this video

and think about it in the context of electronegativity.

Just as a reminder, we talk about electronegativity

in many videos,

but this is the property of an atom that's in a bond

to hog electrons,

to want the electron density to be closer to it

for the electron pairs to spend more time

around that particular atom.

So, something with a high electronegativity

is going to be greedier with the electrons

than something with a low electronegativity.

We can think about the spectrum between

at this end you have ionic,

and at this end you have covalent.

And one way to think about it is at the extreme left end,

you don't have much difference in electronegativities.

Both atoms that are participating in the bond

are roughly equal in how badly they want the electrons.

While in an ionic bond,

you have a very big difference in electronegativities,

so much so that one of the atoms swipes an electron

from the other.

So, one way to think about it is,

let me draw a little bit of an arrow here,

so this is increased electronegativity

difference as you go from left to right.

And some place in the middle,

or as you go from left to right,

you're becoming more and more polar covalent.

So for example, if you have a bond

between oxygen and hydrogen,

these are both nonmetals.

So this will be a covalent bond

by just our general rule of thumb.

And actually the division between metals and nonmetals,

I'm gonna make it right over here,

it's this blue line is one division you could view,

although things that straddle it

are a little bit more interesting.

But oxygen and hydrogen are both nonmetals,

but you have a pretty big difference in electronegativities.

This right over here is electronegativity

measured on a Pauling scale,

named after the famous biologist and chemist, Linus Pauling,

and you can see on that scale oxygen is a 3.44,

one of the most electronegative atoms.

Electronegativity trends, we talk about in other videos,

goes from bottom left to top right.

The things at the top right that are not the noble gases,

these are the ones that really are greedy with electrons.

And oxygen is one of the greediest.

While hydrogen, it's not not electronegative,

but it's lower, at 2.20.

So in this scenario,

those electrons are going to spend more time

around the oxygen.

If they spent an equal amount of time,

that oxygen might be neutral,

but since they're spending a little bit more time here,

we'll say that has a partial negative charge,

the Greek lowercase letter delta,

and on the hydrogen side

because the shared electrons are spending more time

around the oxygen than around the hydrogen,

you would have a partially positive charge right over there.

And so this would be a polar covalent bond.

Maybe on the spectrum it sits right over there,

depending on how you wanna,

how you view this scale.

Now the other question you say is

okay, this is a spectrum between covalent and ionic,

what about metallic?

Well, metallic bonds are in general going to be formed

if you have two things that are not so different

in electronegativity,

and they both have reasonably low electronegativities.

So that's why things on the bottom left right over here,

if you have two of these forming bonds

with each other somehow,

that you're likely to have metallic bonds.

And that makes sense because in metallic bonds

you have all the electrons kind of mixing in

in a shared pool,

which gives some of the properties like conductivity.

And so if you have a lot of things

that are fairly similar in electronegativity,

and they're all low in electronegativity,

they might be more willing to share those valence electrons

in a communal pool.