Published JANUARY 2019

What are atoms made of?



What are atoms made of? 

As we learned in the last animation, the word atom means uncuttable and when John Dalton first discovered evidence that atoms exist, he gave them that name because he suspected they truly were uncuttable. He thought they were fundamental particles, the smallest bits of matter that exist. 

It turns out he was wrong. Atoms are made of subatomic particles, most importantly: electrons, protons and neutrons. Protons and neutrons appear to be made of smaller particles still and truth be told, we don’t know for sure if there really is an end to smallness. Reality might just keep going on forever the further you zoom in. 

This image is made of data collected from an actual scan of a single nitrogen atom, fixed to a metal surface. What we’re actually seeing is the outside of its electron cloud. The colors here are artificial but this is the shape of a nitrogen atom. 

To the right is a simplified model of nitrogen. This type of model is called the Bohr model. Others do exist which are more accurate, more detailed, but when first being introduced to chemistry the Bohr model is the easiest to make sense of so it’s what we’ll be using here.

In the center of this nitrogen atom we have the nucleus. It can’t be seen in the scan because the electron cloud is in the way and in our model, it’s been dramatically enlarged so that we can actually see it. If the model were more realistic, the nucleus would be smaller than a single pixel on your screen. 

In fact if we enlarged the atom to the size of an official soccer field, actually, the size of 10 professional soccer fields, the nucleus would be a about the size of a house spider. 

The nucleus consists of one or more protons and in most atoms, a collection of neutrons. These are what give the atom most of its mass. For example, a gold atom which has 79 protons and typically 118 neutrons, is far heavier than an nitrogen atom which only has only 7 protons and usually 7 neutrons.

The number of neutrons in a particular type of atom, might vary between individuals. For example, while most nitrogen atoms have 7 neutrons, some have just 6 while others have 8. Changing the number of neutrons inside an atom won’t do much to change its chemical properties, it will simply make it heavier, lighter, or in some cases, it will make the atom unstable.

On the other hand, if you were to add or subtract just a single proton from nitrogen (assuming you had the technology to do so), you would completely change its properties. So much, in fact, that we would no longer call it nitrogen. Adding a proton to a nitrogen atom would transform it into an oxygen atom. Taking a proton away from oxygen, would transform into carbon.  

When you look at the periodic table, you find that each element has a number. Hydrogen is number 1, nitrogen is number 8, gold is number 79. This number tells you how many protons a single atom of that element contains.

Protons are positively charged, Neutrons are neutral. 

[Proton = positive, neutron = neutral]

Electrons, on the other hand, are negatively charged. We often depict them as little particles in orbit around the nucleus like planets orbiting a Sun. This isn’t really accurate, in reality, electrons are better described as wave functions that would look a little something like this, if drawn out, but we’re not going to worry about that here. 

In general, the number of electrons an atom has is equal to the number of protons it contains in its nucleus. This is because each positively charged proton attracts 1 negatively charged electron. That said, through chemical reactions, an electron can sometimes be stripped away from an atom, or an extra electron can sometimes be added. 

So to sum things up, what are atoms made of? 

In the center of an atom we find protons and in most atoms we also find neutrons. Protons are positively charged, neutrons are neutral. The number of protons an atom has, determines the type of atom it is. 

Hydrogen has one proton, oxygen has 8, gold has 79 and so on. 

Orbiting about the nucleus, we find electrons. In general, the number of electrons an atom contains, is equal to the number of protons in the nucleus. 

That is the anatomy of an atom, Stated Clearly