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Draw CH3SH Lewis structure.

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What is CH₃SH, and Why Should We Care?

 

CH₃SH, or methyl mercaptan, is an organic compound that’s commonly found in nature. A cousin to alcohol (ethanol), methyl mercaptan might not be as popular, but it plays its own unique role. Often, it's used as an intermediate in the production of other chemicals. However, what's interesting is its smell: this molecule is responsible for the distinct odor of rotten cabbage or stale beer. Ever caught a whiff of that? Well, now you know whom to thank (or blame).

CH₃SH, or methyl mercaptan, is an organic compound that’s commonly found in nature. A cousin to alcohol (ethanol), methyl mercaptan might not be as popular, but it plays its own unique role. Often, it's used as an intermediate in the production of other chemicals. However, what's interesting is its smell: this molecule is responsible for the distinct odor of rotten cabbage or stale beer. Ever caught a whiff of that? Well, now you know whom to thank (or blame).

 

 

Diving into the Structure:

Drawing the Lewis structure is like sketching the portrait of our molecule. It gives us insight into the placement of atoms, bond formation, and the presence of lone pairs. Lewis structures depict how valence electrons are distributed in a molecule or ion.

 

1. Determine the total number of valence electrons needed to fill the octet (octet rule).

Think of the octet rule as the canvas size for our molecular art. For our molecule CH₃SH, which stars 4 hydrogens, 1 carbon, and 1 sulfur, we need to determine the space (or electrons) each actor demands. With carbon and sulfur desiring 8 electrons and hydrogen being content with just 2 (given its humble first-period status). Based on this, the number of valence electrons this molecule supports is 2 x 8 + 4 x 2 = 24 electrons needed to fill the octets.

 

2. Determine the total number of valence electrons that must appear in the structure.

To paint our masterpiece, we need to understand the shades (or electrons) each atom brings. Carbon, the backbone, carries 4 electrons with its 2s² 2p² configuration. Sulfur, with its deep 3s² 4p⁶ ensemble, contributes 6. The hydrogens, ever-so-light with their 1s¹ touch, bring 4 (1 each). Combine these, 4 + 6 + 4 x 1 = 14, and you have a palette of 14 valence electrons.

 

3. Find the number of bonds.

Nr. of bonds = ½ × (Total electrons for octet - Available valence electrons) = ½ ​× (24−14) = ½ ​× 10 = 5 bonds

 

4. Draw the skeletal formula of the compound.

Since there are 5 bonds, and we know that hydrogen is monovalent, carbon tetravalent, and sulfur divalent, this is the only possible structure of CH3SH.

CH3SH structure

 

5. Find the lone electronic pairs of the atoms in the molecule and distribute them in order to fill the octets.

Nr of lone electron pairs = ½ ​× (Valence electrons – Bond electrons) = ½ × (14−(5×2))= ½ ​× 4 =2 lone electron pairs.

 

The Lewis structure of CH3SH is:

CH3SH Lewis structure

Lewis Theory and Covalent Bonds

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In the previous video,
we talked about Lewis theory and ionic bonds.
In this video, we'll talk about covalent bonds.
We're going to describe the Lewis structure of covalent compounds.
Covalent compounds take place between nonmetals.
We're going to describe 2 examples,
water H_2O and oxygen difluoride, which is OF_2.
Let's begin with water.
Hydrogen has 1 valence electron,
and oxygen has 6 valence electrons,
2 pairs and 2 single electrons that are unpaired.
When the molecule is formed,
1 electron from hydrogen shares with
1 electron from the oxygen to form what we call a bond pair.
Now we have a bond pair between hydrogen and oxygen,
and the other one between oxygen and hydrogen.
I've indicated 1 electron in red and 1 in blue,
but it doesn't really matter because electrons are indistinguishable.
Another way of writing this is to indicate a bond pair by a single line,
that's a single covalent bond.
A bond pair to form
is single covalent bond.
We have 2 bond pairs.
In addition, we can add the pairs of electrons on the oxygen.
These pairs of electrons are called lone pairs.
We have lone pairs and bond pairs.
Now if we look at H_2O,
we can count the number of electrons around each atom.
Around hydrogen, there are 2 electrons,
that we call it duplet.
Around oxygen, there are 8 electrons,
we call that an octet,
another duplet, and we can do the same thing in this picture.
If we look at the oxygen,
2 electrons for each bond pair,
and 2 electrons for each lone pair giving a total of 8.
Now let's look at OF_2.
Fluorine has 7 valence electrons,
3 pairs and 1 unpaired electron.
Oxygen has 6 valence electrons as we saw before.
You'll see electrons in the other fluorine.
The unpaired electrons, fluorine can share with
the unpaired electron on the oxygen to form a bond pair,
and each bond pair we saw before,
can be written as a single straight line.
Once again, we can add all the lone pairs.
We have 3 lone pairs around fluorine and 2 lone pairs around the oxygen.
Once again, we can count the number of electrons around each atom,
around fluorine there's an octet,
around oxygen another octet,
around fluorine another octet.
One thing we should notice is that we've counted some of the electrons more than once.
For example, fluorine has 7 electrons,
oxygen has 6,
and fluorine has 7.
That's a total of 20,
and if we counted an octet,
an octet and an octet that means we've counted 24 electrons.
Some electrons are being counted more than once.
Now we're going to describe
a coordinate covalent bond which is a variant on the covalent bond.
Now in our previous examples,
H_2O and OF_2,
each atom contributed 1 electron to the bond pair.
However, sometimes 1 atom contributes both electrons to the bond pair.
This is called a coordinate covalent bond.
Once it's formed, it seemed distinguishable from a covalent bond.
But when it's formed,
it's a coordinate covalent bond.
Let's take an example.
Going to discuss the reaction of ammonia with hydrogen chloride.
Let's look at the Lewis structure of ammonia.
Ammonia has 3 single bonds connecting the nitrogen with each of the hydrogens.
In addition, it has a lone pair,
so that makes an octet,
2 electrons in each of the bond pairs,
and 2 electrons from the lone pair,
a total of 8 electrons.
HCl has a single bond,
so hydrogen has a duplet around it,
and chlorine has a bond pair,
and another 3 lone pairs.
Now what happens when they combine is that
all the electrons in this bond pair go to the chlorine.
Now, chlorine has 1 electron more than it started with.
It started off with 7 and now it has 8,
so it has an additional electrons,
so it's chlorine minus with an octet around it.
Hydrogen is left without any electrons at all.
Hydrogen is H plus,
so we've gone to H plus plus Cl minus.
Now the lone pair on the nitrogen combines with the hydrogen plus.
The nitrogen donates its lone pair to hydrogen plus,
and we get NH_4 plus.
Here are the single bonds.
We have 4 single bonds between the nitrogen and 4 hydrogens,
and the whole species has a positive charge, it's called ammonium.
Now we have ammonium plus and chlorine minus.
We have ammonium chloride.
Now NH_3 ammonia is called a Lewis base because it donates a pair of
electrons and HCL is called a Lewis acid because it accepts a pair of electrons.
In this video, we discussed single covalent bonds,
and also coordinate covalent bonds.
This video discusses covalent bonds, which take place between nonmetals. It explains the Lewis structure of covalent compounds, such as water (H_2O) and oxygen difluoride (OF_2). It also explains the concept of a coordinate covalent bond, which is a variant of a covalent bond where one atom contributes both electrons to the bond pair. This is demonstrated through the reaction of ammonia (NH_3) with hydrogen chloride (HCl), which forms ammonium chloride (NH_4Cl). The video also explains the concepts of Lewis bases and Lewis acids, which donate and accept electrons, respectively.

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