The Periodic Table

The Big Questions

Who developed the first modern periodic table?

How did he organize it, and how does this differ from the organization of the P. T. today?

What are some ways in which we group elements on the P. T.?

What does this tell us about the atom’s structure?

The First Modern P. T.

Developed in 1869 by Dmitri Mendeleev.

Russian chemist and inventor.

Arranged elements according to inc. atomic mass

and periodicity.

Periodicity – tendency of elements to repeat

properties.

Example: Lithium is a metal that reacts explosively

with H2O.

This property is repeated in Na, then again in K, and

so on...

Dmitri Ivanovich Mendeleev

The First Modern Periodic Table

The First Modern P. T.

DM noticed there were “holes” where no

known element would fit.

Guessed that these holes represented

undiscovered elements.

Made predictions about their properties.

When discovered, these elements matched

their predicted properties.

Periods (Rows)

Periods – horizontal rows of elements.

All elements on a period have the same

number of energy levels.

Periods

How many energy levels would you expect to find in atoms

from the 4th row? The 5th row?

Families of Elements

Families – columns or groups.

Elements in a family have similar chem.

properties.

Also have same no. of valence e-.

Coincidence? (No.)

Ions

Atoms can lose or gain electrons.

Ion – an atom that has become charged by

gaining or losing electrons.

Cation – positive ion (lost e-)

Anion – negative ion (gained e-)

Ions

Gain 1 e-

C-

6 p+

7 e-

C

6 p+

6 e-

Lose 1 e-

C+

6 p+

5 e-

The Octet Rule

Atoms tend to gain or lose electrons so

they can have 8* valence electrons (same e-

configuration as a noble gas).

Why?

8 valence electrons = full s and p sublevel.

Extremely stable configuration.

*There are a few exceptions to this rule that

we will discuss later.

Families of the Periodic Table

Group 1A (1)

Alkali metals

1 val. e-

Form +1 ions.

Group 2A (2)

Alkaline earth metals

2 val. e-

Form +2 ions.

Families of the Periodic Table

Groups 3B – 2B (3 – 12)

Transition metals

Have variable val. e-

Can form multiple cations.

Group 3A (13)

Boron group

3 val. e-

Form +3 ions.

Families of the Periodic Table

Group 4A (14)

Carbon group

4 val. e-

C and Si rarely form ions. All others: +2 or +4

Group 5A (15)

Nitrogen group

5 val. e-

Form –3 ions (except for bismuth: +3)

Families of the Periodic Table

Group 6A (16)

Chalcogens

6 val. e-

Form –2 ions.

Group 7A (17)

Halogens

7 val. e-

Form –1 ions.

Families of the Periodic Table

Group 8A (18)

Noble gases

8 val. e- (exc. He)

Do not form ions.

Blockss-

blo

ck

p-blockd-block

f-block

Metals, Metalloids, and Nonmetals

Metals

Majority of elements are metals

Conductors of heat and electricity.

Lose electrons (form + ions).

Nonmetals

About 16 elements.

Insulators.

Tend to gain or share e-

Metals, Metalloids, and Nonmetals

Metalloids

Between metals and nonmetals.

Semi-conductors.

Lose or share electrons.

Metals, Metalloids, and Nonmetals

Metals

Metalloids

Nonmetals

Metallicity

More Metallic Less Metallic

Mo

re M

etall

icL

ess

Met

all

ic

Electron Configs. on the P. T.

1s

2s

3s

4s

5s

6s

7s

3d

4d

5d

6d

4p

5p

6p

7p

3p

2p

1s

4f

5f