2. the periodic table of elements
serve as arespiratory of
information of more than a
hundred elements. the arrangement
of the elements in the periodic
table had gone through several
modification as more information
about each elements were found
out.
3. the very first version of the periodic table was developed in the nineteenth
century. in 1869, two chemist- Juluis Lothar Meyer (german) and Dmitry
Mendeleev (Russian)- separately proposed the arrangement of elements
based on increasing atomic masses. meyer came up with the same
arrangement, but Mendeleev published the idea firts.
Five years earlier, however, English chemist John A.R. Newland already
attempted to established the idea an arrangement based on increasing
atomic masses and observed regularities every eight element, hence called
the law of octaves. But the idea was not accepted by the scientific
community becuase of irregularities with elements beyond calcium.
4. The proposal of Mendeleev was an improvement of
Newland’s efforts. With his arrangement, Mendeleev gave
a more reliable grouping of elements that share similar
chemical properties.
He also used the Sanskrit word “eka” (meaning “firts” to
refer to some elemets. For example, eka-alumimum (Ea) -
now name gallium- to have a mass of 68 amu. Gallium (Ga)
has a measured ato ic mass of 69.9 amu and chemical
properties of eka-aluminum. However, inconsistencies and
discrepancies were later noted for the other elements such
as argon (Ar), which was predicted to have an atomic mass
greater than potassium (K).
5. In 1991, English scientist Henry Gwyn
jeffreys Mosely realized that aside from
atomic mass, atomic number is another
property that support periodicity. The atomic
number, which relates to the number of
protons in the nucleus of an atom, determines
the order of elements in the table. this
arrangement is described as periodic because it
reflects the repeating chemical properties of
elements as will .
