The document summarizes the key contributors to the development of the periodic table of elements from the 1600s to 1940s. It describes how scientists like Brand, Lavoisier, Dobereiner, de Chancourtois, Newlands, Meyer, Mendeleev, Moseley, and Seaborg arranged the known elements and contributed concepts and discoveries that led to the establishment of recurring trends in properties reflected by the modern periodic table. Their work established the periodic law stating that elements' properties repeat periodically with increasing atomic number.

1. DEVELOPMENT OF PERIODIC TABLE OF ELEMENTS
Prepared by: Ms. Mary Grace Nezel T. Cruz

2. In 1969 hennig brand
- German Alchemist who attempted to create a
Philosopher’s Stone - a compound that is said to
be capable of turning things into gold.
- His experiment led him to discover the element
phosphorus
- Robert Boyle was was also able to identify the
same element independent of Brand. Although his
method was different, Boyle was the first one to
publish the element’s discovery.

3. In 1789 Antoine lavoisier
- Arranged all the known elements during his
time.
- He developed The Table of Simple Substances -
which listed new and old names or terms for
elements like oxygen, hydrogen, phosphorus,
sulfur, gold, and mercury, to name a few.
- He also discovered oxygen, and its
involvement in the process of combustion.

4. In 1817 Johann dobereineir
- He is a German Scientist who observed that the
atomic mass of the element strontium (Sr) is an
average between the atomic masses of calcium (Ca)
and barium (Ba) which are said to have similar
properties.
- He noticed how certain elements with similar
properties formed into groups of three.
- He concluded that the elements can be grouped
into triads.

5. In 1862 alexander emile beguyer de chancourtois
- He is a French Geologist who
developed the telluric screw.
- TELLURIC SCREW is a device
printed all the identified
elements on a sheet wrapped
around a cylinder.
- The design was meant to
display elements with similar
properties in a vertical line
and arrange them according to
increasing atomic masses.

6. In 1864 John newlands
- He is a English
Chemist who organized
the 56 known elements
into eleven groups
according to similar
physical properties.
- Elements which
differed by 7 in their
atomic masses had
matching properties.
- He formulated the Law
of Octaves.

7. In 1864 julius lothar meyer
- He is a German Chemist who produced a periodic
table consisting of only 28 elements.
- He organized them in 8 columns, highlighting the
variations in the elements’ properties and their
atoms’ tendency to combine with their atoms.
- His table was surprisingly very similar to
Mendeleev’s but because of a delay in
publication, Meyer’s table was first published a
year later than Mendeleev.

8. In 1869 Dmitri mendeleev
- He is Russian Chemist who had the first recognized
periodic table published.
- He began writing a book entitled Principles of Chemistry
in which he organized the 63 elements known in his time.
- In his construction of the first periodic table,
Mendeleev decided to write each individual element and
its corresponding atomic mass and properties on a blank
deck of cards.
- He organized the elements based on increasing atomic
number.

10. - He gave them temporary names that came with the
Sanskrit word eka which means “first”. He called
the empty space below aluminum, eka aluminum.
- In the modern periodic table, this space is
occupied by gallium (Ga) which has similar
properties with aluminum.
- Mendeleev called the chart “Periodic System” and
referred to the columns as groups and the rows as
periods.
- The abbreviation of its name served as Chemical
Symbol.

11. In 1913 henry moseley
- He was an English Chemist who
discovered that elements are arranged
according to the number of protons in
their atoms.
- He studied the wavelengths and
frequencies of the X-rays and
discovered that each element has X-
rays with unique frequencies.

12. In 1940 Glenn seaborg
- He discovered the transuranic elements (elements after
uranium) transuranium elements and placed the actinide
series below the lanthanide series.
- He made a rearrangement of the periodic table by putting
the actinide series below the lanthanide series.
- In 1951, he won the Nobel prize for his contributions to
the periodic table; the element Seaborgium (Sg) was named
after him.

13. Periodic law
- The contributions of Meyer, Mendeleev, and
Moseley in the development of the periodic
table resulted in the establishment of the
PERIODIC LAW.
- This law states that when the elements are
systematized according to increasing atomic
numbers, their physical and chemical
properties appear in a recurring manner that
allows scientists to predict the possible
placement of undiscovered elements on the
table.