Even More Chemistry!
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Reviewing Ionic versus Covalent
Let's take a look at a super pretty image of the periodic table.
If you think about it, our world is not made by that many components. It's amazing how many combinations we have. And it's all due to the way atoms form molecules!
If you think about it, our world is not made by that many components. It's amazing how many combinations we have. And it's all due to the way atoms form molecules!
We talked about atomic bonds between metals and non-metals, which form ionic bonds.
We talked about bonds between non-metal elements, which forms covalent bonds.
We also know that some molecules can have both, but they are still considered ionic molecules! An example of it can be seen below -- Ammonium Chloride!
Ammonium Chloride is a white, crystalline salt, used in many things, from fertilizer to cough syrups.
Can you tell which one of the bonds below would be ionic, and which ones would be covalent?
We talked about bonds between non-metal elements, which forms covalent bonds.
We also know that some molecules can have both, but they are still considered ionic molecules! An example of it can be seen below -- Ammonium Chloride!
Ammonium Chloride is a white, crystalline salt, used in many things, from fertilizer to cough syrups.
Can you tell which one of the bonds below would be ionic, and which ones would be covalent?
Remember to pay attention. The rule is:
Metal to Non-Metal = Ionic
Non-Metal to Non-Metal = Covalent
And this rule STILL applies! BUT -- You must think of each BOND, not the molecule. So, each individual bond will have their own classification. If ONE bond is ionic, then the molecule is considered an ionic molecule, even if other bonds are covalent.
Metal to Non-Metal = Ionic
Non-Metal to Non-Metal = Covalent
And this rule STILL applies! BUT -- You must think of each BOND, not the molecule. So, each individual bond will have their own classification. If ONE bond is ionic, then the molecule is considered an ionic molecule, even if other bonds are covalent.
Concept question -- metals tend to lose electrons, while non-metals gain electrons -- why is that?
Structure of Ionic Compounds
The structure of ionic compounds (formed by ionic bonds) is arranged in repeating patterns called lattices. The cubic structure of Sodium Chloride is an example of lattice. Take a look below:
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The little cubes of salt are a representation of the lattice structure that is underneath!
This lattice makes the bonds really strong, which causes ionic compounds to have high melting points. It takes a lot of heat to break up these guys!
Another thing that happens de to these lattice structures is that the ionic compounds are hard and brittle.
This brittle characteristic comes from the way the molecules are arranged. Have you noticed how when some materials break, they break with a snap?
This lattice makes the bonds really strong, which causes ionic compounds to have high melting points. It takes a lot of heat to break up these guys!
Another thing that happens de to these lattice structures is that the ionic compounds are hard and brittle.
This brittle characteristic comes from the way the molecules are arranged. Have you noticed how when some materials break, they break with a snap?
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When force is applied to an ionic crystal, this force realigns the matter, and forces atoms with the same polarity to be near each other... which causes the whole thing to yeet itself away from each other.
Ionic compounds also are excellent in conducing electricity, but ONLY IF they are dissolved in water. As you can imagine, in solid form, those crystals are not releasing any electrons; but when you dissolve them in water, the atoms themselves (positive and negative ions) become lose, and those conduct electrical current.
Ionic compounds also are excellent in conducing electricity, but ONLY IF they are dissolved in water. As you can imagine, in solid form, those crystals are not releasing any electrons; but when you dissolve them in water, the atoms themselves (positive and negative ions) become lose, and those conduct electrical current.
So, remember... Ionic bonds are:
- Hard and brittle
- Electrically conductive when dissolved
- Hard to melt
Structure of Covalent Compounds
Covalent compounds share electrons, and they form molecules instead of lattices. Their structure is more diverse in nature.
I mean, we say "share" but it's a bit more like a fight. Imagine a permanent tug-of-war, where both sides pull the rope with equal force: that's a covalent bond. The bond would be the rope.
These bonds, just like ionic bonds, are very hard to break. You can show their structure by using models of atoms. We already worked through Bohr's models; which one, from the ones below, make it easier for you to understand?
I mean, we say "share" but it's a bit more like a fight. Imagine a permanent tug-of-war, where both sides pull the rope with equal force: that's a covalent bond. The bond would be the rope.
These bonds, just like ionic bonds, are very hard to break. You can show their structure by using models of atoms. We already worked through Bohr's models; which one, from the ones below, make it easier for you to understand?
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Structural Model
This is butane. Butane is gas, but it turns into liquid when inside a pressurized canister. The model above is a structural formula. It shows you who connects with who, but doesn't show how the molecule occupies space or how big it is.
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Ball and Stick Model
This is sucrose. When it melts and caramelizes, you can see the colour change, which means different compounds are forming. This type of model is called ball and stick model, and the sticks are the bonds.
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Space-Filling model
When butane burns, it produces CO2, which is colourless and odourless. The model above is a space-filling model, which shows atoms proportionally in space.
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Tadaa, we made creme brulee!
Covalent bonds are strong, but much weaker when comparing to ionic bonds. Their bonds are usually exposed and so they tend to melt with much less heat. They are also relatively soft when comparing to ionic bonds.
Finally, they are not good conductors of electricity, even when melted in water; the reason being, the atoms do not disconnect from each other when in water, but float around as a whole molecule.
Due to their low conductivity, they make excellent wire insulators!
Finally, they are not good conductors of electricity, even when melted in water; the reason being, the atoms do not disconnect from each other when in water, but float around as a whole molecule.
Due to their low conductivity, they make excellent wire insulators!
Did you know?
What if the bond is metal to metal?
Good question!
In that case, something super cool and weird happens.
When a metal bonds with a metal, they release their valence layer, and all the electrons of that layer form a sea of electrons, which freely move around the atoms.
In that case, something super cool and weird happens.
When a metal bonds with a metal, they release their valence layer, and all the electrons of that layer form a sea of electrons, which freely move around the atoms.
When they release that valence layer, these atoms become ions -- Kations, to be more precise. They are kept together by a strong eletrostatic bond which is created between them and the sea of electrons.
This strange, awesome property is what makes metals such a good conductor of electricity.
It also makes metals malleable (making sheets by hammering) and ductible (stretching to make wires), as the atoms move freely in the sea of electrons, changing the shape of the object in question.
This strange, awesome property is what makes metals such a good conductor of electricity.
It also makes metals malleable (making sheets by hammering) and ductible (stretching to make wires), as the atoms move freely in the sea of electrons, changing the shape of the object in question.
Network Solids
Ions are not the only ones who join to make big things.
Sometimes, a molecule organizes itself with other similar molecules to form one giant megamama molecule. This jumble of atoms turns into a giant molecule that organizes itself in a certain way throughout the material.
But sometimes, the same molecules can make different materials! This is because depending on the pressure applied to the material, the molecules will organize themselves in different ways and thus receive different properties from the great molecule gods.
Let's look at Carbon, for instance. Inside a diamond, it forms a network solid, in which each carbon atom will connect with 4 more, and so on and so forth, creating a chain that occupies three dimentions in space. This is what makes diamonds super strong. But Carbon also organizes itself into sheets sometimes, which connect very lightly to each other; each Carbon in a graphite pencil, for instance, combine with three other carbons instead. It does not make a 3D structure, but sheets, and so when you write on a paper, the top layer of that structure slides off onto the paper.
Sometimes, a molecule organizes itself with other similar molecules to form one giant megamama molecule. This jumble of atoms turns into a giant molecule that organizes itself in a certain way throughout the material.
But sometimes, the same molecules can make different materials! This is because depending on the pressure applied to the material, the molecules will organize themselves in different ways and thus receive different properties from the great molecule gods.
Let's look at Carbon, for instance. Inside a diamond, it forms a network solid, in which each carbon atom will connect with 4 more, and so on and so forth, creating a chain that occupies three dimentions in space. This is what makes diamonds super strong. But Carbon also organizes itself into sheets sometimes, which connect very lightly to each other; each Carbon in a graphite pencil, for instance, combine with three other carbons instead. It does not make a 3D structure, but sheets, and so when you write on a paper, the top layer of that structure slides off onto the paper.
Are Atoms all Equally Tiny?
In relative terms, every atom is ridiculously tiny. However, if you were the size of a Hydrogen atom, then you would notice a big difference between their sizes. Check out the table below for the relative size of atoms!
