Understanding Atoms: Structure, Particles, and Elements

Now, just like living organisms are made up of lots of tiny cells, everything, whether it's living, non-living, or even

a cell itself, is made up of lots of tiny particles, which we call atoms. In fact, they're so tiny that a

single cell probably contains more than 100 trillion of them. And in today's video, we're going to explore just what

these atoms are and what they're made of. The first thing to know is that each atom is made up of multiple smaller

particles and its basic structure is a central nucleus surrounded by electrons which orbit around the nucleus in rings

that we call shells. Although we've only shown one electron orbiting here, in reality, all of the

electrons would be moving all the time. The nucleus itself is made up of two different types of particles,

protons and neutrons, which are packed together in a tight ball. Now, the most important thing to

remember here is the structure of the atom that we've just been through and also the relative mass and charge of

each of the particles. The protons and the neutrons have the same mass. So, we say that they

both have a relative mass of one. Electrons, meanwhile, are comparatively tiny and have a mass 2,000 times

smaller, which is often written as just very small or sometimes even zero. Charge is a bit different though.

Protons are positive and have a 1 plus charge. And you can remember this as both proton and positive begin with a P.

Neutrons have no charge. So we say they're neutral. And this is even easier to remember because the words neutron

and neutral both start exactly the same way. Lastly, electrons have a negative charge, which is the same size as the

positive charge of the proton. So, minus one. It can be easy to get all of these mixed up, but the best way to remember

it is that we have positive protons and neutral neutrons. And then we know that the electrons are the only one left. So,

they must be the negative ones. And remember that both of the particles in the nucleus have a relative

mass of one, but the electrons on the outside are much tinier. The size of an atom depends on which

element it is. And we'll see what elements are in the next video, but basically they are the different types

of atoms. In general, we can say that atoms have a radius of around 0.1

nanome. Most of an atom is actually empty space because we measure from the nucleus all the way to the outer

electrons orbit. It's kind of like the solar system. You have one big thing in the

middle and lots of smaller things orbiting it. But between these things is mostly empty

space. Now, although it looks pretty big in this picture, the nucleus is actually really tiny. If we compared its width to

the width of the atom itself, the nucleus is 10,000 times smaller. Although the electrons are

actually even smaller, and if we were to draw them to scale, they'd be too small to see.

In this atom that we've drawn, we have three protons in the nucleus and three electrons orbiting it. Because the

number of protons and electrons is equal, the positive and negative charges balance out. And so overall, the atom is

neutral. Atoms can lose or gain electrons though, in which case the charges would no longer balance and the

overall atom would become charged. When this happens, we stop calling it an atom and instead call it an

ion. For example, if we gave our atom an extra electron, we'd still have three protons,

but four electrons. And so, the charges would no longer balance, and it would now be a

negative ion because there's more negative electrons than positive protons. We'd call this a 1us negative

ion because it only has one extra electron. While if our ion had another extra

electron, it would then have two extra electrons overall and be a 2 minus negative

ion. On the other hand, if an atom loses electrons, then there'd be more positive protons than negative electrons. So,

we'd get a positive ion. And in this case, we have three positive protons, but only two negative electrons.

So our ion would have a 1 plus charge. Now we take a look at it in detail in another video but this here is

the periodic table and each box in the table represents a different type of atom which we call an

element. So this box here represents the element oxygen and this one is the element lithium.

We call these boxes nuclear symbols and they tell us a whole bunch of information about the

element. To see exactly what they tell us, let's take a look at the nuclear symbols of oxygen and

lithium. The first thing to notice is the elemental symbol, which is the one or two letter symbol that represents

that element. So O represents oxygen and L I represents lithium. Then in the bottom left corner we have

the atomic number which tells us how many protons the atoms of that element have. So all oxygen atoms have eight

protons and all lithium atoms have three protons. And this is actually really important as it's the number of protons

in an atom that determines which element that atom is. Lastly, in the top left, we have the

mass number, which tells us the total number of neutrons and protons in that atom. So, if we wanted to find out how

many neutrons oxygen has, we would do the mass number minus the atomic number, which in this case would be 16

minus 8. So, it has eight neutrons. The number of neutrons an atom has isn't always the same as the number

of protons, though. For example, lithium has a mass number of seven. So to find the number of neutrons lithium has, we

would do 7 minus 3, which equals 4. So lithium has four neutrons, even though it only has three

protons. As we said at the beginning of the video, the number of protons and electrons in an atom is always the same.

So, the atomic number also tells us how many electrons the atom has, which means oxygen would have eight electrons and

lithium would have three. If you haven't heard yet, you can find all of our videos on our website,

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