The Nucleus: Crash Course Chemistry #1

Summary

In this engaging script, Hank Green introduces the audience to the beauty of chemistry, emphasizing its crucial role in understanding the world. He explains the atomic theory, the significance of atoms and molecules, and how Einstein's mathematical proof of Brownian motion confirmed their existence. Green also delves into the structure of the atomic nucleus, the role of protons and neutrons, and the concept of isotopes, highlighting the importance of the atomic number in defining elements and the nucleus's role in chemical reactions.

Takeaways

• 🧪 Chemistry is presented as an amazing and beautiful science that can enhance our understanding and enjoyment of the world.
• 🌐 The script emphasizes that chemistry is not just a bridge between particle physics and biology, but a comprehensive field with wide-ranging applications.
• 🔬 Einstein's mathematical proof of the existence of atoms and molecules in 1905 is highlighted as a pivotal moment in the acceptance of atomic theory.
• 🌿 The concept of Brownian motion, first observed by Robert Brown and later explained by Einstein, is introduced as evidence for the existence of atoms.
• ⚛ Atoms are described as the building blocks of everything, composed of protons, neutrons, and electrons, with specific properties based on their arrangement.
• 🔢 The atomic number, determined by the number of protons in an atom's nucleus, is identified as the defining characteristic of an element.
• 📊 Neutrons play a crucial role in stabilizing the nucleus by preventing protons from repelling each other due to their positive charge.
• 📚 The script explains that the relative atomic mass of an element is the average number of protons and neutrons, which can vary due to the presence of isotopes.
• 📉 Isotopes, which have different numbers of neutrons but the same number of protons, result in fractional relative atomic masses for elements.
• 🔠 The chemical symbol 'Ag' for silver is used to illustrate the historical naming conventions of elements and their symbols in the periodic table.
• 🎓 The episode concludes by emphasizing that while the nucleus defines the element, it is the electrons that participate in chemical reactions and determine many of an atom's properties.

Q & A

What is Hank Green's main argument for chemistry being an important science?

Hank Green argues that chemistry is important because it provides a deeper understanding of the world, holding the secrets to life's origins, cancer cures, technological advancements, and the sustainability of life on Earth.

What does Hank Green describe as the 'biggest idea of all time' in the context of chemistry?

The 'biggest idea of all time' Hank Green refers to is the atomic theory, which states that all matter is made from atoms.

How did Einstein contribute to the acceptance of the atomic theory?

Einstein contributed by mathematically proving the existence of atoms and molecules through his explanation of Brownian motion in 1905.

What is Brownian motion and how is it related to the proof of atoms?

Brownian motion is the random movement of particles, such as pollen grains in water, caused by collisions with smaller, unseen particles, which Einstein theorized to be atoms and molecules.

What are the three subatomic particles that make up atoms?

The three subatomic particles are protons, neutrons, and electrons.

What is the function of protons, neutrons, and electrons in an atom?

Protons are positively charged and located in the nucleus, neutrons are neutral and also in the nucleus, providing stability, while electrons, which are negatively charged, orbit the nucleus and are responsible for chemical reactions.

Why is the number of protons in an atom significant?

The number of protons, also known as the atomic number, determines the identity of an element and is the defining trait of an atom as listed in the periodic table.

What is the difference between an element and an isotope?

An element is defined by its number of protons, while isotopes are variants of the same element that have different numbers of neutrons, resulting in different mass numbers but the same chemical properties.

Why are neutrons important in an atom even though they don't change the element's identity?

Neutrons are important because they provide stability to the nucleus by acting as a buffer between protons, preventing them from repelling each other due to their like charges.

What is the term used to describe the total number of protons and neutrons in an atom's nucleus?

The term used is 'mass number', which is different from relative atomic mass, which is an average of all isotopes of an element.

What is the significance of the chemical symbol and how is it used in the script?

The chemical symbol, along with the atomic number and mass number, is used to uniquely identify an element or isotope. It is part of the notation that includes the charge to indicate the number of electrons.

How does the script differentiate between the importance of the nucleus and the electrons in an atom?

The script differentiates by stating that the nucleus, containing protons and neutrons, defines the element and remains unchanged in chemical reactions, while electrons, which participate in chemical bonding, are where all the interesting chemistry happens.

Outlines

00:00

🌟 Introduction to Chemistry's Wonders

Hank Green introduces the subject of chemistry, emphasizing its beauty and importance in understanding the world. He argues that chemistry is not just a school subject but a key to unlocking the secrets of life, technology, and the environment. Green discusses the atomic theory, which posits that everything is made of atoms, and highlights Einstein's role in proving their existence through the explanation of Brownian motion. The video sets the stage for a deeper dive into the atomic structure, emphasizing the roles of protons, neutrons, and electrons.

05:06

🔬 The Atomic Nucleus and Its Role in Elements

This paragraph delves into the atomic nucleus, explaining its composition of protons and neutrons and its significance in defining an element's identity. The atomic number, determined by the number of protons, is highlighted as the key characteristic of an element, with silver (Ag) used as an example to illustrate how the symbol is derived from historical naming. The paragraph also discusses the role of neutrons in stabilizing the nucleus and the concept of isotopes, which are atoms of the same element with different numbers of neutrons, affecting the relative atomic mass but not the chemical properties. The distinction between mass number and atomic mass is clarified, and the video concludes with a note on the correct pronunciation of 'nucleus'.

10:08

📚 Conclusion of the Atomic Nucleus Discussion

The final paragraph of the script wraps up the discussion on the atomic nucleus, summarizing the key points covered in the video. It reiterates the importance of Einstein's work in confirming the existence of atoms through Brownian motion, the definition of elements by their atomic number, the stabilizing role of neutrons, the reason behind non-whole numbers for relative atomic masses due to isotopes, and the distinction between the unchanging nuclei and the more dynamic electrons, which are responsible for the chemical behavior of elements.

Keywords

💡Chemistry

Chemistry is the scientific study of the composition, structure, properties, and reactions of matter. It is central to understanding the world at a molecular level and is the main theme of the video. The script emphasizes that chemistry is not just a 'bridge' between other sciences but a comprehensive field that encompasses a wide range of phenomena, from the creation of life to the development of technology.

💡Atoms

Atoms are the basic units of matter and the defining structure of elements. They consist of a nucleus containing protons and neutrons, surrounded by electrons. The video uses the concept of atoms to explain the fundamental building blocks of all substances, highlighting Einstein's role in proving their existence through the explanation of Brownian motion.

💡Electrons

Electrons are subatomic particles with a negative charge that orbit the nucleus of an atom. They are crucial for chemical reactions and are the focus of the 'interesting chemical stuff' as mentioned in the script. Electrons determine the chemical properties of elements and are responsible for the formation of chemical bonds.

💡Protons

Protons are subatomic particles found in the nucleus of an atom, carrying a positive electric charge. Their number defines the element, as stated in the script with the example of silver having 47 protons. Protons are key to understanding atomic number and the identity of elements.

💡Neutrons

Neutrons are neutral subatomic particles in the nucleus of an atom, alongside protons. They play a stabilizing role by preventing protons from repelling each other due to their like charges. The script explains that while neutrons do not change the element's identity, they do affect the relative atomic mass.

💡Nucleus

The nucleus is the central part of an atom, composed of protons and neutrons. It is described in the script as 'boring' because it remains unchanged in chemical reactions and is thousands of times smaller than the entire atom. The nucleus is the defining characteristic of an element due to its stability.

💡Atomic Number

The atomic number is the number of protons in the nucleus of an atom, which determines the identity of the element. The script uses the atomic number to explain the uniqueness of elements, such as gold with 79 protons or praseodymium with 59.

💡Isotopes

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. The script mentions silver having two stable isotopes with different numbers of neutrons, which results in different mass numbers but the same chemical properties.

💡Relative Atomic Mass

Relative atomic mass is the weighted average of the masses of an element's natural isotopes, taking into account their abundance. The script explains how the presence of isotopes, like those of silver, results in fractional relative atomic masses, such as 107.8682 for silver.

💡Brownian Motion

Brownian motion is the random movement of particles suspended in a fluid, observed by Robert Brown, and later explained by Einstein as evidence for the existence of atoms. The script uses Brownian motion as a historical example of how atoms were proven to exist.

💡Periodic Table

The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. The script refers to the periodic table as a tool for identifying elements by their atomic number and understanding their defining traits.

Highlights

Hank Green introduces the beauty of chemistry as a science that can deepen our understanding of the world.

Chemistry is presented as the key to understanding life's origins, cancer cures, technology advancements, and sustainable living.

Chemistry is described as a bridge between particle physics and more visible sciences like biology.

The atomic theory is explained as a well-tested set of ideas, not just a guess, with Einstein's proof of atoms' existence in 1905.

Einstein's mathematical proof of Brownian motion validated the existence of atoms and molecules.

The concept of atoms as indivisible units of matter is clarified, with the acknowledgment that they can be split, as seen in nuclear reactions.

The role of subatomic particles—protons, neutrons, and electrons—is detailed in forming the structure of atoms.

The atomic number, defined by the number of protons, determines the element's identity.

The chemical symbol 'Ag' for silver is explained, highlighting the historical naming of elements.

Nuclei are described as stable and unchanging, defining the characteristics of elements in chemical reactions.

Neutrons' role in stabilizing the nucleus by preventing proton repulsion is discussed.

The concept of isotopes is introduced, explaining how they affect relative atomic mass but not chemical properties.

The difference between relative atomic mass and mass number is clarified, with examples from silver isotopes.

A notation system for writing atomic information, including atomic number, mass number, and charge, is presented.

The pronunciation of 'nucleus' is discussed, with a recommendation for its correct usage.

A summary of the episode's key points about atoms, their confirmation, elements, isotopes, and atomic nucleus is provided.

Transcripts

Hello, I'm Hank Green and I want to teach you chemistry.

But please, do not run away screaming.

If you give me five minutes to try to convince you that chemistry is not torture,

but instead the amazing and beautiful science of stuff,

and if you give it a chance it will not only blow your mind but also give you a deeper understanding of your world.

This is just my opinion here,

but I think that understanding the world leads to greater ability to enjoy the world

and there's nothing that helps you understand the world better than chemistry.

Chemistry holds the secrets to how life first formed, how cancers are cured,

how iPhones have bigger hard drives than 5 year old laptops,

and how life on this planet might just be able to continue thriving, even ours, if we play our cards right.

Chemistry is the science of how three tiny particles, the proton, the neutron, and the electron,

came together in trillions of combinations to form, get this, everything.

Now chemistry is a peculiar science,

sometimes talked about as a bridge between the ultra abstract world of particle physics

and the more visible sciences like biology.

But calling chemistry a bridge is like calling Eurasia an island.

Chemistry has it all, mad scientists, world changing revelations, the practical, the impractical,

medicine, bombs, food, beauty, destruction, life and death, answers to questions you never knew you had.

I love chemistry, and I hope I can give you a glimpse into why.

So today, let's start out with maybe the biggest idea of all time, and move on from there:

stuff is made from atoms.

[Theme Music]

I know, you aren't shocked, you aren't awed, you might not even be paying attention any more,

but when atomic theory was first proposed, it sounded pretty crazy.

And yes, we call it 'Atomic Theory', using the scientific definition of theory,

which is "a well-tested set of ideas that explains many disparate observations",

not the colloquial definition of theory, which is "a guess."

But luckily there's no-one running around any more saying "atoms are just a theory."

But it wasn't that long ago that people were running around saying that.

You wanna know who settled it for good? Einstein!

Atoms had been postulated for a long time by the 20th century,

but it wasn't until Einstein mathematically proved the existence of atoms and molecules in 1905

that the matter was truly settled.

And you thought Einstein was all about relativity and E=mc2, he also proved atoms exist!

Here's how it happened:

In 1827, a botanist named Robert Brown was looking at pollen grains in water through a microscope

and he noticed that they jiggled randomly even when there was no movement to cause the jiggling.

It was a mystery for a long time.

Until 1905 when Einstein theorized that this phenomenon was caused by

as-yet-unproven atomic particles actually smacking into the grains of pollen.

He wrote up some fancy math, showing that his theory predicted this motion almost perfectly,

and everyone had to concede that yes, tiny discrete bits of matter were indeed smacking into the pollen,

and thus molecules, and by extension atoms, must exist.

Today, we remember this botanist and his discovery by calling the motion he observed Brownian motion.

It's kinda crazy that every physical thing you've ever interacted with is made up of little ball thingies.

It started with people wondering what would happen if you just kept slicing something in half forever.

Eventually, and of course it turns out that there's no knife sharp enough to do this,

you end up with one, pure, unbreakable bit of that substance.

The word "atom", indeed, is from the Greek for "indivisible",

though, of course, as we learned in World War II, atoms can be broken as well.

So all the stuff that we think of as stuff is made of atoms, tiny discrete particles that have specific properties,

depending on the arrangement of three simple subatomic particles.

There's the proton, heavy and positively charged, the neutron, about the same size as the proton but neutral,

and the electron, which has the same amount of charge as the proton, just opposite,

and very nearly has no mass at all, about 1800 times less massive than the proton or neutron.

Protons and neutrons hang out in the nucleus, and thus are the nuclear components or nucleons;

electrons hang out around the nucleus and are the parts of the atom that do all the interesting chemical stuff.

But before we get to the chemistry of the electrons, we first have got to understand the properties of the nucleus.

Okay, this is pretty important, so pay attention here.

The number of protons in an atom determines what element it is.

79 protons: always gold. 59 protons: always praseodymium.

The number of protons in an element is its atomic number.

It sits right on top of the box in the periodic table because that is the element's defining trait.

So an atom of silver with 47 protons in its nucleus is always an atom of silver.

Depending on what its electrons are doing and what it's bonded to,

it might be part of a chemical that's silver-colored or black or blue or shiny or poisonous or a cure for disease,

but whatever it is, that atom is still silver and will remain an atom of silver probably forever,

because that core number is very, very difficult to change.

Now you might have noticed something weird about silver here:

it's chemical symbol, the one- or two-letter short code that tells you what it is, is Ag,

not Si, which is silicon, or Sv which is perfectly available, but Ag. Why? To torture you? No.

Silver, of course, because we've known about it for a long time, was one of the first elements added to the periodic table,

and back then it was called "argentum", Latin for "shiny gray stuff."

Also, the root of the word "Argentina",

where Spanish explorers heard rumors of mountains made of silver, which of course did not exist.

The name "Argentina", just like the chemical symbol "Ag", stuck,

despite neither of them being particularly representative of reality. Now, back to science.

Nuclei, which is the plural of nucleus, are boring.

They're thousands of times smaller than the atom as a whole,

and they mostly just sit around being exactly the same as they were when they were first

created billions of years ago,

held together by the strongest of the four fundamental forces of physics, the strong nuclear force.

The fact that nuclei are so boring is the very reason they're the defining characteristic of elements.

While electrons can jump from atom to atom whenever it's convenient,

the number of protons is almost always extremely stable.

So that core of the atom, the nucleus, always comes out of chemical reactions unscathed.

It's the bit that we can bump around from reaction to reaction,

but always remains pure and behaves the same way as any other atom with that number of protons.

The atomic number is the soul of the atom. It's what makes it it.

Neutrons are important too, of course, in their own way, but they don't change what element an atom is.

One of the two keys to all things chemical is charge, we'll discuss that in another episode,

and since neutrons don't have any charge, they mostly don't change the properties of an atom.

But they are, nonetheless, vital.

We all know that like charges repel each other. Neutrons serve as a kind of buffer between the protons.

You couldn't pack silver's 47 protons together in the nucleus by themselves.

They couldn't handle it; they'd rip themselves apart.

So nuclei only clump together permanently when the right number of protons and neutrons get together.

Silver needs about 60 neutrons to space out the 47 protons correctly. But it doesn't have to be 60.

In fact, silver nuclei are also very stable with 62 neutrons.

61 though, that doesn't work, and the reasons for that, I don't know, you would have to talk to a nuclear physicist.

The atomic number of silver doesn't change as the number of neutrons changes

because the number of protons stays the same.

But the relative atomic mass does change.

Relative atomic mass, which used to be called atomic weight back when I was in school,

is basically the number of protons plus the number of neutrons averaged across all the silver on Earth.

Because silver has two different stable isotopes, each with a different number of neutrons,

its relative atomic mass ends up not being a whole number.

About 52% of silver has 60 neutrons and about 48% has 62.

The relative atomic mass, then, ends up being about halfway between 107 and 109, 107.8682.

You'll note that I said these two different sorts of silver are called isotopes,

they have different masses but the same chemical properties,

and are the same element and so belong in the same place on the periodic table.

In fact, the word "isotope" means "same place".

And different isotopes have different mass numbers.

The mass number is just the total number of nucleons in the nucleus, which is different from atomic mass.

It's simple addition for a single atom, rather than an average of all the relative atomic masses of all the silver atoms on Earth.

So silver has two stable isotopes, one with a mass number of 107, which we'd call silver-107,

and one with a mass number of 109, silver-109.

There's an easy way to write all this out, of course, to keep your information straight.

The chemical symbol, with the atomic number or number of protons here,

the mass number, or number of protons and neutrons here,

and the charge out here, which tells you by simple addition or subtraction how many electrons there are.

Finally, before we conclude this first episode of Crash Course Chemistry,

and thus, our discussion of the atomic nucleus, a note on the pronunciation of "nucleus".

You are welcome to say "nuculus", it is an accepted pronunciation of that word,

but if you can find it in you, it's probably best to switch over to "nucleus", which is, after all, how it's spelled.

And that is all for today's episode of Crash Course Chemistry, if you were paying attention, you now know:

More about atoms than anyone did in 1900,

like that they were finally confirmed when Einstein mathematically defined Brownian motion;

That elements are chemically pure substances,

and the type of element an atom is is defined by how many protons it has in its nucleus, or its atomic number;

That neutrons stabilize nuclei for their proton friends;

That different isotopes of the same element are the reason relative atomic masses are never whole numbers;

and you know that nuclei are the uninteresting, boring bits of the atom,

and the electrons are where all the interesting chemical-ly stuff happens.

Crash Course Chemistry is filmed, edited, and directed by Nick Jenkins,

Dr. Heiko Langner is our Chemistry consultant, sound design is done by Michael Aranda,

and our graphics team is Thought Bubble.

If you have any questions, comments, or ideas on any of this stuff we will endeavor to answer

them in the comments below.

Thank you for watching Crash Course Chemistry.