Using 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

Li

HHe

For these elements the last electron is in the s orbital

for these elements the last electron is

in the p orbitalFor these elements the lastelectron is in the d orbital

For the elements the last electronis 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 AlIt is the first element in the 2nd row of p filling elementsThe 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 repetitiveInstead it is condensed, by starting from the previous Noble gas and adding shells to it.For example K[Ar]4s1

This is the same as saying everything that is in Ar (1s22s2p63s2p6) +4s1

Zr[Kr]5s24d2

-> [Kr] 4d25s2

To Determine the Condensed electron

configuration

Start at the previous noble gas (lower atomic number)Write out every element in order of atomic number to your givenDetermine which shell all elements are filling. The number of elements in that shell is your superscript number.

For Iron

Previous Noble Gas----Ar

Write all elements

K Ca Sc Ti V Cr Mn Fe

These fill 4 s

These fill 3 d

So it is

[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 O