MODERN ALCHEMIST

Periodic Table

Dimitri Mendeleev developed the periodic table in 1869. After developing the periodic table, he used it to predict the existence of atoms which had not yet been discovered.

A table with the element symbols is provided below:

H                                                  He
Li Be                               B  C  N  O  F  Ne
Na Mg                               Al Si P  S  Cl Ar
K  Ca Sc Ti V  Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y  Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I  Xe
Cs Ba La Hf Ta W  Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac Rf Ha

The periodic table is arranged so that atoms located in a column have similar chemical properties.

H, Li, Na, K, etc., are known for their tendency to lose an electron to become a positive ion.
He, Ne, Ar, Kr, etc., are called the "Noble Gases"; they almost never participate in chemical reactions.
The atoms F, Cl, Br, I, etc., are called "halogens", and are known for their tendency to accept an electron.

The next few pages will discuss these ideas in greater depth.

There is a "discontinuity" in the transition between what we learned when drawing Auf-Bau buildup diagrams, and the format of the periodic table. This discontinuity arises because the when atoms come together to form molecules, molecular orbitals form, which may be hybrids of the atomic orbitals. Shortly you will study hybridization.

Previously, we drew atoms by placing the electrons in the series of sublevels as follows: 1s (red), 2s (orange), 2p (yellow), 3s (green), 3p (blue), etc. These sublevels are the atomic orbitals mentioned in the previous paragraph.

H                                                  He
Li Be                               B  C  N  O  F  Ne
Na Mg                               Al Si P  S  Cl Ar
K  Ca Sc Ti V  Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y  Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I  Xe
Cs Ba La Hf Ta W  Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac Rf Ha

Let's look at the rows of the periodic table:

The first row contains 2 atoms
The second row contains 8 atoms
The third row contains 8 atoms
The forth row contains 18 atoms
The fifth row contains 18 atoms

We can draw atoms with shells corresponding to rows in the periodic table. Below we see argon, with 2 electrons in the first shell, 8 electrons in the second shell, and 8 electrons in the third shell.

A periodic table is shown below, with elements colored in a way to correspond to the sublevels.

Elements colored lime-green end with an 's' subshell
Elements colored purple end with a 'p' subshell
Elements colored turquoise end with a 'd' subshell

Currently, the Web Elements provides the best periodic table resource I've found on the web.

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