I received this question about the basics of the periodic table. Far from being dumb questions these are the neccessary things to know in order to be able to use the table. MJ writes:

I'm guessing my "question"(s) will go unanswered as they no doubt will be deemed (probably accurately) as a missive from a moron.  At last, my misspent youth has caught up to me.  I took ONE chemistry class -- during summer school at a different high school, so it wouldn't affect my grade point standing -- and I got through it, but I wasn't exactly electrified by it.  Now, I feel like a moron so I decided to "learn" the periodic table.  Ha!  I can't even figure it out.   I gather the actual element numbers (1 - 118) are just a way of identifying an element?  And why does it break at 57, separating out 58 - 71 and 89 - 103?  And there are little numbers inside the boxes.  What are they all about?  Also, to what do the Group (and subgroup?) numbers refer?  For example 18 on top, 8A under that?  (Yes, I'm blonde, but let's just get past that.)

And elements 113 - 118:  If they "exist," why aren't they on the table.  If we don't know what they are, how have they been determined to exist?  Ah well, this may be more than one can handle in a simple email, but I appreciate any enlightenment you can shed.  And, of course, keep my password "simple."

1) The 'actual element numbers' are called the atomic number which is also the number of protons in the nucleus, the electrical charge of the nucleus and the number of electrons in an unbonded atom of an element.

2) The table doesn't really 'break' at 57 and 89. The f-block elements (58-71 and 90-103) actually fit right in where the go numerically, but this makes the table very wide. In order to make it fit onto a normal page, those elements are just shown below where they would go, and the gap is closed up.

3) The 'little numbers inside the boxes' is the atomic weight. The atomic weight of an element is the average weight of an atom in atomic mass units which is abbreviated u or often amu.

4) Groups are the vertical columns of the table, and they're important because elements in groups have similar chemical properties. They're numbered 1-18 just so you can talk about which group without needing to name off a bunch of elements. The Roman numeral numbering system is an old system that indicates how many electrons are available for bonding in elements of a particular group.

5) All of the elements with an atomic number higher than 92 are man made. Elements 113, 115 and 117 have not yet been made. These transuranium elements are made inside atom smashers and are identified by mass spectrometry and other techniques.
  11:11:08 PM   comments