ATOMIC NUMBER

1. HOW DID THE CONCEPT OF ATOMIC
NUMBER LEAD TO THE SYNTHESIS OF
NEW ELEMENTS IN THE LABORATORY?

2. Chemists in 19th century generally agreed
about what particles consisted matter and
agreed that matter consisted of atoms.
However, they knew nothing about the
structure of the atoms.

3. The information about the known elements
gave them inspiration to arrange the elements
in a table.

4. JOHN ALEXANDRIA REINA
NEWLANDS
In 1864, J.A.R Newlands, an
English chemist noticed that
when the elements were
arranged according to
increasing mass, every eighth
element would exhibit similar
properties, better known as
the Law of Octaves.

5. Li Be B C N O F Na Mg Al
7 9 11 12 14 16 19 23 24 27
Si P S Cl K Ca
28 31 32 35.5 39 40

6. ARRANGEMENT OF ELEMENTS ACCORDING
TO NEWLANDS

7. DMITRI IVANOVICH MENDELEEV
A Russian chemist who developed the
periodic classification of the elements.
Mendeleev found that, when all the
known chemical elements were arranged
in order of increasing atomic weight, the
resulting table displayed a recurring
pattern, or periodicity, of properties
within groups of elements.

8. JULIUS LOTHAR MEYER
A German chemist who also worked
on a periodic table. Meyer’s table
only included twenty-eight elements,
which were not classified by atomic
weight, but by valence.

9. This periodic table, although
remarkably successful, had some
inconsistencies.

10. HENRY GWYN JEFFRIEYS MOSELEY
English physicist who experimentally
demonstrated that the major properties
of an element are determined by
the atomic number, not by the atomic
weight, and firmly established the
relationship between atomic number
and the charge of the atomic nucleus.

11. When Moseley arranged the elements in the
periodic table by their number of protons
rather than their atomic weights, the flaws in
the periodic table that had been making
scientists uncomfortable for decades simply
disappeared.