Metallic Bonding

Summary

In this chemistry essentials video, Mr. Andersen explains metallic bonding through the electron sea model, where delocalized electrons are shared among metal atoms. This model accounts for metals' conductivity, malleability, ductility, and low volatility. However, the shell model is necessary to understand anomalies in melting points across transition metals. The video explores how electron configurations, particularly unpaired electrons in d orbitals, affect these properties, with a focus on the transition from high to low melting points as electrons fill and pair in the d subshells.

Takeaways

• 🔬 Metallic bonding involves a number of atoms sharing their electrons, forming a 'sea of electrons'.
• 🌊 The electron sea model is the primary way to visualize metallic bonding, where electrons are delocalized and free to move.
• ⚡ Metals exhibit high conductivity due to the presence of free electrons that can easily flow through the material.
• 🔨 Malleability in metals is explained by the electron sea model, allowing atoms to slide past each other when hammered.
• 🔩 Ductility is the property of metals to stretch rather than break when pulled, due to the freedom of atoms to move around each other.
• 🔥 Metals have low volatility, which means they have high melting and boiling points, attributed to the strong attraction between the sea of electrons and the positive charges in the nucleus.
• 📉 The electron sea model does not fully explain the variation in melting points across transition metals, necessitating the shell model for a complete understanding.
• 📚 The shell model becomes important when discussing the electron configurations of transition metals, especially to explain anomalies in melting points.
• 🌐 The electron configurations of transition metals often involve unpaired electrons in d orbitals, contributing to their metallic properties.
• 📉 The melting point of transition metals does not consistently increase with the number of electrons; it can dip, as seen with chromium, due to its unique electron configuration.
• 🚫 As we move towards nonmetals, like zinc, the properties of metals start to change, showing a deviation from typical metallic behavior.

Q & A

What is the electron sea model in the context of metallic bonding?

The electron sea model is a way to visualize metallic bonding where electrons are delocalized and shared among a number of atoms, creating a 'sea' of electrons that are free to move within the structure of the metal.

Why can't there be just one metallic bond?

Metallic bonds involve a collective sharing of electrons among multiple atoms, so there must be a group of atoms to form this type of bond, not just one.

What properties of metals does the electron sea model account for?

The electron sea model accounts for properties such as conductivity, malleability, ductility, and low volatility of metals.

How does the electron sea model explain the conductivity of metals?

In the electron sea model, the free electrons can easily flow through the metal, which allows for the conduction of electricity and heat.

What does malleability mean in terms of metals?

Malleability refers to the property of metals that allows them to be hammered or rolled into thin sheets without breaking, due to the smooth sliding of atoms in the metallic bond.

What is ductility, and how does it relate to metallic bonding?

Ductility is the property of metals that enables them to be stretched into wires without breaking. It is related to metallic bonding because the atoms have the freedom to move around each other, allowing the metal to stretch rather than fracture.

Why do metals have low volatility?

Metals have low volatility because of the strong electrostatic attraction between the positively charged protons and the delocalized negatively charged electrons, making it difficult to separate the atoms and turn the metal into a liquid or gas.

How does the electron sea model relate to the melting point of metals?

The electron sea model suggests that metals with more free electrons should have higher melting points due to the stronger electrostatic attraction. However, this is not always the case, and the shell model is sometimes needed to explain variations in melting points.

What is the significance of unpaired electrons in transition metals?

Unpaired electrons in transition metals contribute to the properties of metals by allowing for greater freedom of movement of electrons within the electron sea, which is essential for metallic bonding and the associated properties.

Why does the melting point of metals not consistently increase as you move across the transition metals?

The melting point of metals does not consistently increase across the transition metals because factors such as electron configuration and the stability of the electron shell structure can influence the melting point more than just the number of valence electrons.

What is the difference between the electron sea model and the shell model in explaining metallic bonding?

The electron sea model focuses on the delocalized electrons shared among metal atoms, while the shell model delves into the specific electron configurations within the atoms, which can help explain phenomena like variations in melting points that the electron sea model cannot account for.

Outlines

00:00

🔬 Metallic Bonding and Electron Sea Model

Mr. Andersen introduces the concept of metallic bonding in this chemistry essentials video, emphasizing that it involves a collective sharing of electrons among multiple atoms, forming a 'sea of electrons.' This electron sea model is key to understanding metals' properties such as conductivity, malleability, ductility, and low volatility. The video explains how the delocalized electrons provide metals with the ability to conduct electricity and heat, and how the atoms' freedom to move allows for malleability and ductility. The electron sea also contributes to metals' high melting and boiling points due to the strong attractive forces between the positive and negative charges. The video hints at the need for the shell model to explain variations in melting points across different transition metals.

05:03

📉 Electron Configurations and Melting Points in Transition Metals

This paragraph delves into the relationship between electron configurations and the melting points of transition metals. It discusses how adding electrons to the valence shell generally increases the melting point due to the increased electrostatic attraction. However, the pattern is disrupted when the 4s subshell is filled before the 3d subshell, as seen with chromium, leading to a dip in melting point. The video highlights the importance of electron pairing in affecting the properties of metals, noting that paired electrons reduce the number of free electrons available for conductivity and other metallic properties. The summary of electron configurations from scandium to zinc illustrates the transition from metals to nonmetals and the corresponding change in properties, concluding with the observation that metallic bonding can be understood through the delocalized electron model to predict macroscopic properties of metals.

Keywords

💡Metallic Bonding

Metallic bonding refers to the type of chemical bonding that occurs between metal atoms. It is characterized by the delocalization of electrons, which are shared among a lattice of metal cations. In the video, metallic bonding is central to understanding the properties of metals, such as their conductivity, malleability, and ductility. The electron sea model is used to illustrate this concept, where electrons are free to move throughout the structure, contributing to the metal's unique characteristics.

💡Electron Sea Model

The electron sea model is a theoretical framework for understanding metallic bonding. It describes a 'sea' of delocalized electrons that surround positively charged metal ions. This model is crucial in the script for explaining the physical properties of metals, such as their ability to conduct electricity and heat, as well as their malleability and ductility. The script uses this model to show how the free movement of electrons within the 'sea' allows for these properties.

💡Delocalized Electrons

Delocalized electrons are electrons that are not associated with a particular atom but are free to move throughout a structure, such as in a metal lattice. In the context of the video, delocalized electrons are key to the electron sea model and are responsible for the metallic properties like conductivity and malleability. The script mentions that these electrons have the freedom to move and repel each other, which is why they drift around and create the electron sea.

💡Conductivity

Conductivity in the script refers to the ability of metals to conduct electricity and heat. This property is directly related to the presence of delocalized electrons in the electron sea model. The script explains that because electrons are free to move, they can easily facilitate the flow of electric current and transfer heat throughout the metal, making metals excellent conductors.

💡Malleability

Malleability is the property of a material that allows it to be hammered or rolled into thin sheets without breaking. In the video, malleability is attributed to the metallic bonding, specifically the electron sea model, where the delocalized electrons allow metal atoms to slide past each other easily. The script gives the example of a blacksmith using this property to create gold leaf by repeatedly hammering gold into a very thin sheet.

💡Ductility

Ductility is the property of a material that allows it to be stretched into a wire. In the script, ductility is another key property of metals that arises from metallic bonding. The video explains that when metals are pulled, the atoms can slide past each other due to the presence of delocalized electrons, allowing the metal to stretch rather than break, as demonstrated by the tensile strength test in the script.

💡Low Volatility

Low volatility in the context of the video refers to the high melting and boiling points of metals. This is due to the strong electrostatic attraction between the delocalized electrons and the positively charged metal ions within the electron sea. The script explains that this strong attraction makes it difficult to overcome and turn the metal into a liquid or gas, resulting in high melting and boiling points.

💡Melting Point

The melting point is the temperature at which a solid substance turns into a liquid. In the video, the melting point of metals is discussed in relation to the electron sea model and the shell model. The script notes an unexpected trend in the melting points of transition metals across a period, which initially increases with the addition of electrons but then dips, suggesting a need for the shell model to explain this phenomenon.

💡Shell Model

The shell model is an alternative to the electron sea model for understanding the properties of atoms, particularly their stability and reactivity. In the video, the shell model is introduced to explain the anomalies in the melting points of transition metals. The script discusses how the electron configurations, specifically the filling of the 4s and 3d subshells, can affect the melting points of these metals.

💡Transition Metals

Transition metals are a group of elements in the periodic table known for their ability to form multiple oxidation states and their involvement in various catalytic processes. In the script, transition metals are highlighted as having many unpaired electrons in their d orbitals, which contribute to their metallic properties and the effectiveness of the electron sea model in predicting their behavior.

💡Electron Configurations

Electron configurations describe the distribution of electrons in an atom's orbitals. In the video, electron configurations are used to explain the behavior of transition metals, particularly in relation to their melting points. The script discusses how the filling of the 4s and 3d orbitals affects the stability of the metal atoms and, consequently, their melting points, with the example of chromium not filling its 4s orbital before moving to the 3d orbital.

Highlights

Understanding that you can't have one metallic bond; you need a number of atoms together sharing their electrons.

Metallic bonding is visualized through the electron sea model, where electrons are shared by all the atoms, creating a sea of electrons.

In metallic bonding, we have delocalized electrons that have the freedom to move.

The electron sea model accounts for the properties of metals, such as conductivity, malleability, ductility, and low volatility.

Sometimes, the shell model is needed to explain phenomena like melting points in metallic bonding.

Positive charges of protons are held inside the sea of negative charge electrons, which are constantly in motion.

Transition metals, which have a lot of unpaired electrons in their d orbital, are a key focus in metallic bonding.

Metals are good at conducting electricity and heat because of the free electrons that can flow easily.

Metals are malleable, meaning they can be flattened out without breaking, a property used by blacksmiths to create gold leaf.

Metals show ductility, meaning they can stretch rather than break when pulled, unlike brittle materials.

Metals have low volatility, resulting in high melting and boiling points due to the strong attraction between positive and negative charges.

The electron sea model explains properties well, but the shell model is needed to explain the melting point trend across transition metals.

Melting points increase across the period but show a dip at chromium due to electron configurations.

The melting point pattern picks up again after magnesium, where electrons start pairing, leading to lower melting points towards zinc.

Understanding the delocalized electron model helps predict macroscopic properties of metals like conductivity, malleability, ductility, and low volatility.

Transcripts

Hi. It's Mr. Andersen and this is chemistry essentials video 21. It's on metallic bonding.

And it's important that you understand that you can't have one metallic bond. You have

to have a number of atoms together sharing their electrons. And therefore sharing their

bonding. And so the way we look at metallic bonding is the electron sea model where you

have all of these electrons. And they're shared by all the atoms. It creates a sea of electrons.

And then the protons are kind of held on the inside of that. And so in metallic bonding

what we have are delocalized electrons. Or electrons that have the freedom to move. And

the way we visualize that is through this electron sea model. It accounts for a lot

of the properties of metals. Like their conductivity, malleability, ductility, low volatility. And

sometimes we have to go to the shell model however to explain new phenomena. And we'll

get to that when we're looking at melting point. And all of that has to do with bonding.

And so if we look at metallic bonding or these shared bonds between all the metals, visualize

it like this. We have the positive charges of the protons in the nucleus. And then we

have electrons that are free to go. They don't want to get too close to each other. Their

going to repel each other. And so what they do is they simply drift around. And they're

constantly in motion. And what you create is this sea of electrons that have a negative

charge. And then the protons are going to be held on the inside of that. And that's

the best way to visualize the metallic bonding. And remember these are going to be transition

metals. So these are going to be atoms that have a lot of unpaired electrons in their

d orbital. And as a result these electrons have a freedom to move. And as a result we

have all of these properties that come from metals. So number 1 they are very good at

conductivity. So that means conducting electricity and also conducting heat. And the reason why

is that electricity for example is simply the flow of electrons. And so if we have free

electrons it's easy for them to flow through that metal. Likewise with heat, since those

electrons and those atoms have a huge amount of freedom, we can move a lot of that energy

through the material. They also are incredibly malleable. And what malleable means is that

you can hit them and they are going to flatten out. And so if you're a blacksmith you're

using that property of heating up these atoms in the metallic bonds. And then as you hit

it you're able to slide them past one another. It's going to be smooth sliding. And that

explains how we could get something like gold leaf which is simply gold that we hit over

and over and over again until it's razor thin. They also show ductility. And what ductility

means is that it's ductile. Or that means that if we pull it, it's going to stretch

rather than break. And so if we were to test the tensile strength of different materials,

so what you do is you put them in a big vice like this. Then you simply pull on it. If

something is ductile what that means is as you pull on it it's going to stretch out before

it eventually breaks. If it's not, it's brittle. What it's going to do is simply break in half.

And metals show this. And the reason they show that is that all of these atoms have

freedom to move around each other. And so when you pull on each other it's going to

stretch it out. They also show low volatility. What that means is that they're going to have

a high melting point and a high boiling point. Why is that? Well think of all the positive

charges we have down in these metals. We have all of these negative charges. And so there's

going to be a huge attraction between the two. And so it's hard to pull off individual

ones to make them a liquid or eventually to make them a gas. And so you would think as

we move across the transition metals, so let's say we're going across this period from scandium

to zinc. As we move across we should be increasing the number of electrons. And so we should

be increasing something like this. Melting point. And it's not really right. And so let's

look at what the data looks like. So as we move across the period, it starts to go up

for awhile, but then it dips. And then it eventually goes down quite a bit. And so this

whole idea of an electron sea model works well. But when you get to something like this,

we have to start digging into the shell model to make sense of it. And so let's start by

looking at some electron configurations. So if we're looking at scandium it's going to

have 2 electrons in its 4s. And that's something interesting about transition metals. They're

valence electrons are actually going to be at a higher level but inside the s subshell.

Anyway, as we move across what we're doing is we're increasing the number of electrons.

So we're increasing the number of valence electrons. And so as we go to titanium and

then as we go to vanadium this all makes sense. If you can increase more of these electrons,

increase more of that charge, it's going to be harder to get this thing to melt. But if

you look here when we get to chromium, it kind of dips. And the reason why is that it

actually is not going to fill this 4s before it jumps into the 3d. And then as we go to

magnesium you get a real stable shell structure where all of these are filled. And so the

melting point is going to drop off. But now that pattern picks up again. Okay. Now we're

going to start adding electrons. So when we go to iron and cobalt and to nickel, now we're

adding these paired electrons. And as we pair those electrons, now we don't have those free

electrons anymore. And so we're going to decrease the melting point as we get all the way down

to zinc. And remember as we get to zinc we're moving over towards those nonmetals. And so

we're starting to see odd properties here as well. And so metallic bonding is pretty

simple. Did you learn to use a delocalized electron model to predict macroscopic properties

of metals? If you understand the sea model and you see how it affects conductivity, malleability,

ductility and low volatility, then you got it. And I hope that was helpful.