Unit 3: Periodic Table Chapter 6

Objectives

21 Understand the historical background of the periodic table including

such contributions of Newlands, Mendeleev, and Moseley

22 Use the periodic table to predict properties of certain elements

23 Identify the difference between periods and groups

24 Identify where main group, metals, metalloids, non-metals, alkali,

alkaline-earth, halogen, noble gases, transition metals, lanthanides

(rare earth metals) and actinides exist on the periodic table along

with their characteristics and electron configurations

25 Define and apply the periodic law to the trends on the periodic table

including atomic radius, ionization energy, and electron

affinity/electronegativity

21 Historical Background on the

Periodic Table The Periodic Table was original designed by

John Newlands and was published in the

1860s.

◦ He also proposed an idea known as the Law of

Octaves to help explain his setup for the table.

More extensive work was done on the

Periodic Table by Dmitri Mendeleev.

◦ He arranged the table by atomic mass.

◦ He left blanks where he felt elements should

belong even though they were not discovered

yet.

Mendeleev’s Periodic Table

Historical Background Continued

While Mendeleev’s table was the first that

resembled our current model, there were

some flaws.

◦ None of the noble gases were present.

◦ There were some discrepancies Mendeleev could

not explain in certain properties.

◦ It did not account for isotopes.

Historical Background Continued

In 1914, Henry Moseley rearranged the

Periodic Table by atomic number.

By doing this, he eliminated the

discrepancies that Mendeleev could not

explain.

Moseley’s table is the model used today with

the elements found after 1914 added to the

table.

22 Characteristics of the Table

The Periodic Table was carefully designed to

provide as much information as possible.

The table is ordered into:

◦ Periods: horizontal rows

◦ Groups: vertical columns

◦ Blocks: S, P, D, or F

23,24 Sections of the Table

There are certain sections of the Periodic

Table that have common properties.

◦ Metals

◦ Metalloids

◦ Non-metals

◦ Main Group Elements

Metals

Shiny

Form positive ions

Ductile

Malleable

High melting and

boiling points

Good conductors

◦ Heat and energy

Return

Non-Metals Make up the majority

of the crust, atmosphere and living organisms

Low melting and boiling points

Form negative ions

Low densities

If solid, tend to be dull and brittle

Poor conductors

◦ Both heat and energy Return

Metalloids

Semi-conductors

Contain some

metallic properties

Contain some non-

metallic properties

Return

Main Group Elements

Made up of the S and

P blocks

Consists of some of

the most common

elements.

Return

Groups and Blocks

Alkali Metals

Alkaline Earth Metals

Transition Metals

Halogens Noble Gases

Actinide Series

Lathanide Series

Alkali Metals

Highly reactive

Rarely found in the

elemental form

Soft metals

Low densities

Make +1 ions

Last electron is

always a s1

Return

Alkaline Earth Metals

Always from +2 ions

Last electron is always an s2

High melting points

Reactive but not as violent as the alkali metals

Return

Halogens

Highly reactive

Form -1 ions

All but astatine can

form a diatomic

molecule

Common in acids

Used as disinfectants

and in pesticides

Return

Noble Gases

Odorless, colorless

gases

Outer (valence)

energy level is full

Very low reactivity

Melting and boiling

points are low and

very close together

Cryogenic

refrigerants Return

Transition Metals

Form the D-Block of

the Periodic Table

Magnetic Properties

◦ 1 or more unpaired

electrons

High melting and boiling

points

Can from +1, +2, +3

ions

Generally solid

Return

Lanthanide Series

Make up the 4f block

Typically used in lasers

Sometimes referred to

as the rare earth

metals

◦ Though actually found in

high concentrations in

the crust

Superconductors

Batteries and magnets

Return

Actinide Series

Make up the 5f-block

Most are man-made

◦ Thorium and uranium are

the only two the occur

naturally with any

abundance.

Radioactive

Return

25 Periodic Law

Certain properties follow periodic law.

Periodic law refers to the increasing or

decreasing of a trend as one progresses

across a period or group on the Periodic

Table.

Three of the most common trends that are

monitored and follow periodic law are

atomic radius, ionization energy, and

electron affinity.

Atomic Radius

Atomic radius refers to the size of the

electron cloud surrounding the nucleus.

The atomic radius increases as each new

energy level is added.

While electrons are being added to an

energy level, electron shielding allows for the

affects the size of the atom.

Electron Shielding

As electrons start filling energy levels, the nucleus holds them close.

As more are added, the inner ring prevents the nucleus from pulling the outer ring too close (it shields the positive charge).

The nucleus will pull the energy level slightly closer though as you progress across the table.

Atomic Radius Trend

The atomic radius increases in the

direction of the arrow.

Ionization Energy

Ionization energy is the energy required to

remove an electron from an atom.

The larger the atom, the more difficult it is

for the nucleus to hold onto its electrons.

Smaller atoms can hold onto electrons much

easier.

Ionization Energy Trend

The ionization energy increases in the

direction of the arrow.

Electronegativity

Electronegativity refers to how well an

atom attracts electrons.

Smaller atoms have more nuclear charge

to attract electrons.

As that large atoms have a difficult time

holding onto their electrons, they do not

readily attract electrons.

Electronegativity Trend

The electronegativity increases in the

direction of the arrow.

This concludes the tutorial on

measurements.

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