Section 4.4—The Periodic Table

History of the Periodic Table

Different scientists organized the elements differently—this lead to confusion

In 1869, Dimitri Mendeleev designed a periodic table based on atomic mass.This way showed patterns in properties that

repeated across rows and similarities down columns

He couldn’t find elements to fit all the property trends, so he left holes

History of the Periodic Table

The holes he left were later filled in as more elements were discovered

The modern periodic table is arranged by atomic number rather than atomic massThis caused a few “switches” in placement, but

overall is very similar to Mendeleev’s

Organization of the Periodic Table

Groups and PeriodsGroupsColumns are called “groups” or “families”Periods

Rows are called “periods”

6C

Carbon12.01

Information for Each Element

Atomic NumberWhole number—elements are ordered by this on the periodic table.

Element SymbolIf there’s a second

letter, it’s lower-case

Element Name

Atomic MassNumber with decimalsGives the mass for 1 mole of atoms, in grams

Most periodic tables give the following information, but it can be in a different location

Parts of the Periodic Table

The rows at the bottom

Most periodic tables are written with 2 rows at the bottom.

This is done to allow the font to be bigger on a piece of paper.

The rows at the bottom

Most periodic tables are written with 2 rows at the bottom.

This is done to allow the font to be bigger on a piece of paper.

But they really belong here!

Follow the atomic numbers on your periodic table to see it!

Electron Configurations and the Periodic Table.

1s2 2s2 2p5

Configurations Within a Group

Look at the electron configurations for the Halogens

F

Cl

Br

I

1s2 2s2 2p6 3s2 3p5

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5

All of the elements in Group 7 end with 5 electrons in a p subshell.

In fact, every Group ends with the same number of electrons in the highest energy subshell

Configurations and the Periodic Table

s1 s2

d1 d2 d3 d4 d5 d6 d7 d8 d9 d10

p1 p2 p3 p4 p5 p6

f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14

d-block

f-block

p-blocks-block

p subshells begin in level 2, so begin the p-block with “2p”

s subshells begin in level 1, so begin the s-block with “1s”

How to remember the filling order?

2p

3p

4p

5p

6p

3d

4d

5d

6d

4f

5f

d subshells begin in level 3, so begin the d-block with “3d”

f subshells begin in level 4, so begin the f-block with “4f”

1s

2s

3s

4s

5s

6s

7s

1s

To see the filling order of subshells, read from left to right, top to bottom!

How to remember the filling order?

2p

3p

4p

5p

6p

3d

4d

5d

6d

4f

5f

1s

2s

3s

4s

5s

6s

7s

1s

Note that this tool shows that the 3d energy level is filled after the 4s energy level!

How do you know where to start off after using a noble gas?Use the periodic table!

Where Does the Noble Gas Leave Off?

2p

3p

4p

5p

6p

3d

4d

5d

6d

4f

5f

1s

2s

3s

4s

5s

6s

7s

He

Ne

Ar

Kr

Xe

Rn

The noble gas fills the subshell that it’s at the end of.

Begin filling with the “s” subshell in the next row to show valence electrons.