Atoms and Things
By Dilys & Doug Griffiths - 06/08/2008
We all know atoms are the basic building blocks of everything but do we know what they look like and how they work?
In the early 20th century, a chap by the name of Bohr had a stab at it, describing things called Electrons having a negative charge, forming a cloud like shell, which is around a ‘heavy centre’ of positive particles and uncharged particles called Protons and Neutrons. Resembling a small solar system in fact.
Ah, but how small is this system? Think of the head of a pin. OK? The top knob would be large enough to hold a million, million atoms with still room to spare! But let’s just have a look at one atom and not confuse ourselves; especially now that we have a clue as to the size of it.
Imagine our atom is shaped something like an egg – after cracking it open of course! The yolk is the ‘heavy centre’. This is filled with particles, which are split into two sections called Protons and Neutrons. The Protons are electrically charged and the Neutrons are not.
There are Electrons around this heavy centre. They are there in order that the atom, as a whole, is electrically neutral. This is very necessary, otherwise things would get mixed up and our atom could become unstable.
Figure One
In order to do their work, the Electrons arrange themselves into circulating orbits, and depend upon the number of Protons in their nucleus for setting up the maximum number of electron-holding orbits required. Every orbit has a set maximum number of Electrons allowed in it.
Where there are many electrons, they settle into their different orbits. If the outer orbiting cloud finishes full, the atom is stable and unable to combine with any other atom. However, the combination of atoms is essential for making our everyday materials – wood, plastic, cotton, water – all matter in fact – including you! How does this happen?
Different materials are made up of different combinations of Protons, Neutrons and Electrons. But, always the number of Protons equals the number of Electrons which arrange themselves together into different ‘clouds’. Each ‘cloud’ has a fixed maximum number of Electrons and can be explained mathematically as a series which begins – 2; 8; 18; 32….like the petals on a some double dahlia type flowers - if you ever care to count the petals!
Here are two of the simplest atoms.
As you can see, Hydrogen has only one Electron in its ‘cloud’. This allows it to combine with other atoms because its cloud can actually hold two.
Helium has a full ‘cloud’ and will not combine with anything.
Now, let’s take the metal Silicon for an example
This nucleus has 14 Protons and 14 Neutrons – therefore it must have 14 Electrons. There will be 2 Electrons orbiting within the ‘cloud’ closest to the nucleus, 8 in the second closest ‘cloud’ and 4 in the final outer ‘cloud’. We already know this final cloud can hold a maximum of 18. The spaces left in this last ‘cloud’, will allow Electrons belonging to the outer ‘clouds’ of other atoms of material to join with Silicon and share together a common ‘cloud’ –to make up compounds like sand and glass.
Electrons orbiting around inside their particular ‘cloud’ – are many in some cases and few in others. It’s a bit mind boggling and , if only we could see it, we might think resembled a section of a small universe.
As an aside, Electrons moving in their outer ‘cloud’ can easily be dislodged by heat or voltage sources, leaving a positively charged atom and drifting Electrons. These, if forced to drift in one direction become an electric current.
The existence of Electrons was known in about 600 BC. The philosopher Thales, who lived to be 94years old, observed that when Amber was rubbed it could pick up light objects like straw and dry grass and he inferred that the Amber produced ‘something’ on its’ surface. If only he could have lived some 2,500 years longer – we could have explained to Mr Thales that his ‘something’ was actually free wandering Electrons.
The mysterious energy which binds together Electrons, Protons and Neutrons is the source of our present day X-rays, Nuclear Fusion and Nuclear Fission.
How does this all happen? – Watch this space!.