Constructing the periodic table chapter 4 & 11

The Periodic Table Arrangement The periodic table is arranged by orbital diagrams. Schrodinger gave us equations that describe atomic orbitals. The values we get from those equations are quantum numbers. We used quantum numbers to build orbital diagrams, we used orbital diagrams to build the periodic table

Using the periodic table to determine orbital diagrams The period relates to the energy level of electrons Therefore H and He only have electrons in the 1st energy level Li, Be, B, C ,N ,O ,F and Ne have electrons up to the 2nd energy level

You can determine the orbital by the placement For these elements the last electron is in the s orbital He Li for these elements the last electron is in the p orbital For these elements the last electron is in the d orbital For the elements the last electron is in the f orbital

Determining the number of electrons in the last energy level count the number of elements to the left edge of the “section” For example Al It is the first element in the 2nd row of p filling elements The last electron for aluminum will be the first electron possible in the 2nd p

Continuing… Al The last electron will be the first possible in the 2nd p 1 s __ 2 s __ p __ __ __ 3 s __ p __ __ __ d __ __ __ __ __

Condensed electron configuration long electron configurations are not normally written out because it gets rather repetitive Instead it is condensed, by starting from the previous Noble gas and adding shells to it. For example K 1s22s2p63s2p64s1 Instead becomes [Ar]4s1 This is the same as saying everything that is in Ar (1s22s2p63s2p6) +4s1

To Determine the Condensed electron configuration Start at the previous noble gas (lower atomic number) Count out every element in order of atomic number to your given Determine which shell all elements are filling. The number of elements in that shell is your superscript number.

For Iron Previous Noble Gas----Ar Count all elements K Ca Sc Ti V Cr Mn Fe These fill 4 s These fill 3 d So it is [Ar] 4s23d6 but we should put the energy levels in order [Ar]3d64s2

Lone electron in the 5d or 6 d Odd exception Lanthanum’s last electron fills the 5d orbital. Ce has its last electron fill in the 4f, and the one from 5d (La) jumps to 4f. The next elements all fill up the 4f until Gadolinium which fills up the 5d again. A similar “jumping” of one electron occurs with the actinide series

Different Periodic Tables The electron “jumping” is why there are two forms of the periodic table in common usage. One has lanthanum and actinium in with the d filling elements. The other has lanthanum and actinium with the f filling elements

Homework For the following elements Ignore the exception if you run into it. fill in the last shell only of the orbital diagram and do the condensed electron configuration Ti, Cl, Sr, Sn and Au