history of the periodic table - powell's...

History of the Periodic

Table

Each group will be given some cards. Can your group

figure out what card is missing? What is it (number

and suit)?

Antoine Lavoisier

In the late 1790s, he compiled a list of the known elements at the time.

This list contained 23 elements.

1743 - 1794

But times were about to change…

In the 1800’s, there were many changes in the world • Electricity

• Spectrometer

• Industrial Revolution

As a result, there was an increase in the number of known elements • By the 1870, there were 70 known

elements

An agreement is reached…

Then in the 1860’s, chemist agreed upon a method for accurately determining the atomic mass of elements.

John Newlands

Noticed when elements were arranged by atomic mass, they repeated properties every 8th element.

He used the word periodic to describe this pattern

He gave it the name the Law of Octaves

1838-1898

Unfortunately…

Did not work for all the elements

Criticized because of its association with music

Did give others the idea of repeating properties - periodic

We Hate It

Lothar Meyer and Dmitri Mendeleev

Each made a connection between atomic mass and properties of elements

1830-1895 1834 - 1907

The winner is…

Mendeleev is given credit because his was published first

In addition, Mendeleev predicted unknown elements

However, not completely correct – new elements weren’t in correct order

What do you notice about elements 27 & 28 and 52 & 53?

Mendeleev

Henry Moseley

Solved this problem by arranging the elements by increasing atomic number.

The periodic repetition of chemical and physical properties of elements when arranged by atomic number is now known as Periodic Law

1887-1915

Which leads to the Modern Periodic

Table

Boxes each with:

H

1

Hydrogen

1.00794

Element Name

Atomic Number

Atomic Symbol

Atomic Mass

That are arranged by increasing atomic numbers

Remember

Atomic number = the number of protons = the number of electrons (if neutral)

Atomic Mass on the Periodic table is the average mass of the isotopes

• But the mass number of each isotope is the protons plus the neutrons

Chemical Symbol

The symbol that refers to the element

First letter is capitalized, second letter (if applicable) is lower case

Not all symbols are based on English names for the elements, some come from their Latin names or even other languages

– Silver – Ag – argentum

– Antimony – Sb -stibium

– Lead – Pb – plumbum

– Copper – Cu – cyprium

– Tin – Sn – stannum

– Iron – Fe - ferrum

– Mercury – Hg - hydrargyrum

– Gold – Au - aurum

Columns and Rows

The columns are called Families or Groups • Earlier Version had 1-8 followed by A or B

Group A elements are called Representative Elements

Group B elements are called Transition Elements

• Modern Version labels the columns with 1-18

Rows are called Periods

• Seven periods for the seven energy levels (rings)

Classifying Elements

Three Types of Elements

• Metals

• Nonmetals

• Metalloids

Metals

Shiny when smooth and clean

Solid at room temperature

• Only exception - Mercury

Good conductors of heat and electricity

Most are ductile and malleable

Most of the elements on the table are metals, which are in blue

Nonmetals

Upper Right side of the Periodic Table

Generally brittle solids or gases

Poor conductors of heat and electricity

Bromine is the only liquid at room temperature

“The Yellow Elements”

Metalloids

A.k.a – the semi-metals

Boxes bordering the stair-step

Physical and chemical characteristics of both metals and nonmetals

“The Green Stair-stepping Elements”