Name: GENERAL CHEMISTRY explained in 19 Minutes
Uploaded: 2026-01-23T15:14:35.000Z
Duration: 18 min 49 s
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Atoms consist of a core and some electrons.

The core is made of protons and neutrons, and

depending on the number of protons, you get different elements.

Quantum mechanics tells us that this is not what atoms actually look like.

For now, just think of atoms as having multiple electron shells.

The electrons in the outermost shell are called valence electro.

Most of chemistry is really just the behavior of these electrons.

Every element is listed in the periodic table.

All elements in the same column or group have the same number of valence electrons.

For the main groups, the number of valence electrons is just the group number from 1 to 8.

Except for helium, it's too small to have eight electrons.

So it's just kind of grouped in with those.

Luckily, the transition metals also follow a nice pattern.

It's kind of a mess, but that's not so important for now, so we'll get to that later.

Elements with the same number of valence electrons tend to show similar behavior in chemical reactions.

For example, the first group without hydrogen is called the alkali metals.

They're kind of soft, and they do this sometimes.

All elements in the same row or period have the same number of shells.

This number increases from top to bottom.

Also, the mass gets bigger from left to right as each element gains a proton, an electron, and

Depending on the number of neutrons in the core, you get different isotopes of the same element, most of which are pretty unstable and fall apart, releasing ion radiation.

If an atom has the same amount of electrons as protons, it has no charge.

If it has more, it has a negative charge, and

if it has less, it has a positive charge.

Negative ions are anions, and positive ions are cations.

The periodic table is also pretty much a dictionary, as every cell tells you the name and symbol of an element.

The number of protons in the core, which is also the total number of electrons, and

the atomic mass, which is the mass of neutrons and protons combined with the periodic table is roughly divided into three categories.

Right of it are the nonmetals, which are mostly gases, and

the Line is called the semimetals, which have properties that fall somewhere in between two or more atoms bonded together form a molecule.

If you have at least two different elements, you get a compound.

This is probably a good time to mention that compounds often behave completely differently than the elements they're made of.

Like put together an explosive metal and a toxic gas and you get, of course, an even more explosive table salt.

For example, the molecular formula, where you just count the number of each atom in a molecule and write them as a subscript number next to the element symbol.

They have the same molecular formula, but obviously they're not the same.

Showing this difference is probably kind of important.

It's the only thing that separates graphite from diamonds, because they're both just fancy versions of carbon.

And I don't think anyone's gonna go, mmm, yes, this dusty black blob is indeed very expensive.

One way to show the structure of an atom is a Lewis dot structure, which represents the valence electrons and bonds as dots and lines.

This is also going to help us understand why atoms bond in the first place.

You see, everything in the universe wants to get to a state of lower energy.

That's why a ball on a hill will roll down by itself, because that decreases its potential energy.

The state of lowest potential energy is having a full outer shell of electrons, which is most often 8.

Or in the case of hydrogen and helium, too.

If you think back to the periodic table, you'll see that all noble gases already have a full outer shell, which is why they don't really want to react.

If two atoms don't have a full outer shell, but

can achieve one by sharing electrons, they will naturally do so the same way a ball will go downhill, as their combined energy would be lower than if they were separate.

The sharing of electrons is called a covalent bond.

These bonds are also caused by the positively charged nucleus of an atom tugging on electrons of another atom.

The strength of this pole is called electronegativity.

In the periodic table, the electronegativity increases from bottom left to the top right.

Therefore, fluorine has the strongest pull.

It's just unbelievably desperate for an electronic.

If the difference in electronegativity is bigger than about 1.7, you get an ionic bond.

Chlorine would do anything for an electron, while sodium has one too many and just kind of wants to get rid of it anyway.

They both say, forming an ionic bond, where sodium loses an electron and turns into a cation and chlorine gains an electron and turns into an anion.

The most common place you see ionic bonds is in salt.

But more generally, when metals and nonmetals bond, you get a salt which is just a grid of I.

Speaking of metals, a pure metal forms metallic bonds.

You can imagine this as a huge grid of positively charged nuclei which are surrounded by freely moving electrons.

You see, in a metal grid, the valence electrons are kinda promiscuous, Whereas the nerds call it delocalized.

They can move freely in a giant playground of nuclei instead of being loyal to just one.

This kind of bond is responsible for the properties of metals like conducting electricity and heat.

And also being malleable, as in being kind of bendy like.

You can hammer on this stuff until it's the most deformed, unelegant and ugly looking piece of material ever known, and

it will just limp along as if nothing ever happened.

If the difference in electronegativity is lower than about 0.5, the electrons are shared pretty equally and you get a nonpolar covalent bond.

smaller than around 1.7, one of the elements is pulling on the electrons pretty hard.

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GENERAL CHEMISTRY explained in 19 Minutes

positive

negative

spontaneous

solid