The Periodic Table

Part One

The Basics

What does periodic mean?

Having or marked by repeated cycles

What things in our everyday life do we notice as cyclic or periodic?

What are some of the patterns you notice on the periodic table?

There are many important people who played a key role in organizing the elements in such an intricate fashion…

Antoine Lavoisier (1790’s)

Compiled a list of

known elements at

the time (23)

What elements do you

think were included

here?

Gold, silver, oxygen,

carbon

The 1800’s brought

about big changes…

What are some big things that may have affected the knowledge of chemistry?

Electricity

Development of the spectrometer

Industrial revolution (mid-1800’s) Lead to many chemical industries…soaps, dyes,

fertilizers

But not all good things came from the revolution Chemical pollution now an issue

70 known elements by the 1870

In addition to new elements…

New scientific data that provided insight into the properties of compounds and elements

A tool for organization became necessary

Big step: 1860 Scientists agreed on a method for accurately

determining the atomic masses of the elements (finally!)

What would be the problem with not having a universal way to measure the mass of elements?

Now the search for relationships between mass and elements was on…

John Newlands (1864)

English chemist

Proposed organization scheme

Noticed elements were arranged by increasing atomic mass

Also, their properties repeated every eigth element 1st and 8th

2nd and 9th

What do were call this repeating pattern?

Newlands called it: The Law of Octaves Octave is a group of musical notes

that repeats every eighth tone

Newlands organized

the first 14 known

elements

Elements with similar

properties were in the

same row

How does this

compare with our

current periodic table

Newlands organized the first 14 known elements

Elements with similar properties were in the same row

How does this compare with our current periodic table

The Law of octaves was not readily

accepted b/c it did not work with all

elements

Newlands law was also criticized b/c the

use of the word octave was considered

very “unscientific”

The important thing was that Newland

recognized that properties of elements

were repeated

Lothar Meyer (1869)

German chemist

Demonstrated connection between atomic mass and elemental properties

Did not receive as much credit as Dmitri Mendeleev because he did not publish his organization scheme first

Dmitri Mendeleev (1869) Russian chemist

demonstrated connection between atomic mass and elemental properties

Noticed (like Newlands) that when elements were put in order of atomic mass there was a periodic repetition of their elemental properties

Arranged elements in order of increasing atomic mass into columns with similar properties

This was the first periodic table

Mendeleev’s table was widely accepted

because it predicted the existence and

properties of undiscovered elements

Blank spaces on the table

Predicted properties of yet to be

discovered elements such as scandium,

gallium, and germanium

But there were problems…

New elements discovered and atomic

masses were more accurately determined

Elements in Mendeleev’s table not in

correct order

Arranging elements by mass now put

groups of elements together with different

properties

Henry Moseley (1913)

English Chemist

Figured out the problem with Medeleev’s Table

What did Moseley Discover before? Atoms of each element

contain unique number of protons in their nuclei

He arranged elements in order of increasing atomic number and not increasing atomic mass

Problem Solved!

Moseley’s arrangement solved the problems with Mendeleev’s table

His arrangement resulted in clear periodic patterns of properties

Lead to Periodic Law:

Statement that there is a periodic repetition of chemical and physical properties of the elements when they are arranged in increasing atomic number

Modern Periodic Table

What’s in the box?

What does the 1 stand for? Atomic Number

This tells us what about an atom of H?

# of protons

What does the 1.007947 stand for? Atomic Mass

This tells us what about an atom of H?

Mass in nucleus (# of protons and neutrons)

On the modern periodic table, how are

elements arranged?

In order of increasing atomic number, left to

right

What do we call the columns (up and

down) on the periodic table?

GROUPS (or families)

What do we call the rows (left and right) on

the periodic table?

PERIODS

What does periodic mean?

Having or being marked by repeated cycles

What element does period 1 begin with?

H

How many periods are there on the table?

7

Periods

Groups Two different number systems for

groups. In the first numbering system, groups are number 1-8 and each number is followed by either an A or B

The groups labeled A are the main groups (1A thru 8A) Representative elements

This is because they possess a wide range of chemical and physical properties

The groups designated with a B (1B thru 8B) are found in the center Transition Elements

A more recent numbering system has been devised numbering 1-18