Virtually all kids know what this is but are mystified by it. Lets try and breathe some life into it.
Assuming a knowledge of elements, protons, neutrons and electrons (carbon has 6 protons so 6 electrons) lets cut to the chase of electronic configuration which shows the number of electrons in each shell surrounding the nucleus. The outer shell of electrons is the most significant. Elements combine to achieve a settlement or stability in their outer shell of electrons (most importantly by sharing electrons so each has a full outer shell). Differant elements with the same number of electrons in their outer shells have similar physical and chemical properties (consider Copper, Silver, Gold in the table, everyone recognises these).
Now remember this. Shells are numbered sequentially outwards from the nucleus and for each shell there is a maximum number of electrons it contains. Shell 1 upto2, Shell2 upto8, Shell3 upto18. Shell 1 has only 1 subshell(s) with 2 electrons. Shell 2 has 2 subshells 2s(2 electrons) and 2p(6 electrons). Shell 3 has 3 subshells 3s (2 electrons), 3p (? yes 6 electrons) and 3d (? yes 10 electrons).
Dont worry if all this information doesnt sink in just now it will and soon you will be able to visualise the shells in their beauty. Click on the picture at the top of the page above to see a larger image of the table.
Do you see group 11, Cu, Ag, Au? They all have similar properties right? shiny metals. Now look at Group 4 and you can see Carbon and Silicon the two key players in life and electronics.
Study Tip! if you are finding it hard to study as an adult why not take a textbook to a coffee shop. As kids we study in classes, large groups but learn to focus with our friends (and non-friends!) around us. Try it. You may be amazed at the focus you achieve.
Now focus. The horizontal rows are called periods. Going across a period each atom has one more proton and therefore one more electron. In the first period there is is one shell of electrons from hydrogen which has one electron to helium which has two electrons (and therefore a full outer shell).
In the second period there are two shells of electrons from lithium upto neon which has 8 electrons in its outer shell Shell 2 (2s with 2 electrons, 2p with 6 electrons). Neons outer shell is full too.
In the third period there are three shells of electrons from sodium upto argon. Argons outer shell is full too.
Helium, Neon and Argon are very stable and settled because their outer shells are full. Much of chemistry is concerned with how elements which dont have full outer shells combine with each other and other elements to achieve full outer shells, settlement and stability. Sometimes the reaction can be explosive!
Arguably much of history is about how peoples with differant ideologies can combine to achieve a settlement and stability. Preferably without reaching for the explosive!
"My outer shell is unfilled and there is only one way to resolve this"
(Picture of a terrorist) You will forgive my caution in not supplying the obvious image.
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