Lesson 1
Development
of the
periodic table
Independent Task
1.
2.
Use power point or word
Create a timeline POSTER showing the evolution of the periodic table (posters will be
displayed on the wall)
3.
It should contain the scientist's name, the year, picture of scientist, P-table
arrangement and significance and problems with their version
4.
You should have the following scientist
1.
John Newlands
2.
Dimitri Mendeleev and Lother Mayer
3.
Enerest Rutherford
4.
Henry Mosely
5.
Modern Periodic table
6.
It can include additional scientist – But the above are most important
5.
Do NOT copy and paste – LOSE marks
Marking Criteria
Visual /Poster
Readable and use of scientific
information
Use of own words/sentences
Included all scientist
Points
1
2
2
1
Meet expectations of point 3
(previous slide)
Understanding significance of
scientist
10
Grammar, spelling, punctuation
BONUS: Additional Scientist and
their importance
2
2
Total Exc BONUS
2
20
Deadline: End of the lesson
Sent to teacher
19th Century
Had some idea of the atom, but did not know the existence of protons and electrons
Scientist had an idea about the atomic mass – Scientist linked atomic mass to chemical
behavior
John Newlands (1864)
Arrangement: Arrange elements with increasing order of atomic mass
Significance: Every 8th element had similar properties (Law of octaves)
Problem: Periodic table was rejected as some metals grouped with nonmetals with dissimilar properties (Also – new elements were being
discovered that did not fit in his table)
Look at Oxygen (O) and Iron (Fe)  They are in the same group, but one is
a metal and the other is a non-metal. They have different chemical
properties
Idea: His idea on law of octaves was rejected by scientific community
Oxygen – Nonmetal
Iron – Metal
Should NOT be in the same group
Dimitri Mendeleev & Lother Meyer (1869)
Arrangement: Arrange elements with increasing order of atomic mass of
66 known elements
Significance:
1. Grouped elements more accurately according to properties
2. Made predictions of properties of elements that had not yet been
discovered
3. He left gaps in his periodic table
Problem:
•Isotopes were discovered long after Mendeléev had proposed his periodic
classification of elements.
•The periodic table cannot accommodate the presently known 118 elements.
•"The atomic masses do not increase in a regular manner in going from one
element to the next. So it was not possible to predict how many elements
could be discovered between two elements — especially when we consider
the heavier elements"
•The elements present in Lanthanides and actinides that were discovered
later, can not be placed in his periodic table.
•The periodic table contains elements of dissimilar properties together and
separates elements of the same properties. Such as barium and lead are,
separated into second and fourth groups.
Idea: Made a positive change in chemistry
Additional issue and
solution
• Atomic Mass was causing reactive elements to
be placed with non-reactive elements • Example: Argon 39.95 and Potassium 39.10
• Recall: Mendeleev did not know about atomic
number (proton)
• Ernest Rutherford – British Scientist
• Conducted an alpha scattering experiment
• He concluded that the center of an atom has
a positive area (he did not know about the
proton)