IIIIII Unit XI: Periodic Properties I. History (p. 123 - 127)

I II III

Unit XI: Periodic Properties

I. History(p. 123 - 127)

A. Mendeleev

Dmitri Mendeleev (1869, Russian)

Elements were put in order of increasing atomic mass.

Elements with similar properties were grouped in columns.

• In some places, masses don’t go in order to complete the pattern. These elements were still assigned to the column their properties matched. (On the assumption that there must be errors in their masses.)

A. Mendeleev

Mendeleev’s table was a major breakthrough because it could predict element properties.

Mendeleev left gaps in locations where no known element had the necessary properties to fit the pattern.

Based on the patterns he’d identified, he predicted properties of three of the “missing” elements.

A. Mendeleev

Mendeleev’s predicted

elements were later

discovered/identified and were found

to have the properties he’d predicted.

B. Moseley

Henry Moseley (1913, British)

(Built on Bohr’s principles of

emission spectroscopy)

Used x-ray spectrometry to determine the number of protons in each element.

This generated the values we now call “atomic number.” (These were not known in Mendeleev’s time.)

B. Moseley

Organized elements in the periodic table by increasing atomic number.

This resolved the mass discrepancies in Mendeleev’s arrangement.

The Modern Periodic Law:

When elements are ordered by atomic number, chemical and physical properties recur periodically.

B. Moseley

The Modern Periodic Law is sometimes stated:

The properties of the elements are periodic function of their atomic numbers.

Graphing by atomic

number shows

repetitive patterns in

element properties.

I II III

I. Periodic Table Vocabulary

Ch. 5 - The Periodic Table

B. Blocks

s pd

f

Main Group ElementsTransition Metals (d-

block)Inner Transition Metals

(f-block)

B. Blocks

A group or “family” is a column on the periodic table, e.g., the alkali metals or the noble gases.

B. Groups

A period is a row on the periodic table– all the way across, regardless of block.

B. Groups

Period 6 includes 6s, 5d, 6p

and 4f

Period 4:

4s, 3d, 4p

I II III

II. Organization of theElements

Ch. 5 - The Periodic Table

MetalsNonmetalsMetalloids

A. Metallic Character

Alkali metalsAlkaline earth metalsTransition metalsLanthanidesActinides

Periodic Table SectionsOther metalsMetalloidsOther nonmetalsHalogensNoble Gases

Elements within a GROUP have similar properties

Because they have similar electron arrangements.

Periodic Table Sections

1s1

2s1

3s1

4s1

5s1

6s1

7s1

Periodic = every so oftenWhen elements are arranged in order of

atomic number, elements with certain properties recur periodically.

The Periodic Table

There is a predictable pattern. It repeats for each PERIOD.

The Periodic Table

Period 3

Na

Mg

AlSiPSCl

Ar

In a PERIOD, atomic radius decreases as atomic number increases.

Atomic Radius

Group 1

H

LiNa

K

RbCs In a

GROUP, atomic radius increases as atomic number increases.

Ionization Energy

Period 3

Na

Mg

Al

Si

PS

ClAr

In a PERIOD, ionization energy increases as atomic number increases. (But not smoothly.)

Atomic Radius

Group 1

H

LiNa K Rb Cs

In a GROUP, ionization energy decreases as atomic number increases.Fr