Slides in this set
The periodic table is a tabular arrangement of the chemical
elements, ordered by their atomic number (number of protons),
electron configurations, and recurring chemical properties. This
ordering shows periodic trends, such as elements with similar
behavior in the same column.
It is called the periodic table of elements because elements with
similar properties occur at regular intervals.
The elements are arranged in order of atomic number (proton
number) so that very similar elements end up in vertical
columns called groups AND they have the same number of
outer electrons (except H and He) which gives them very similar
Most elements are metals on the left and lower parts of the
periodic table. Non-metals are on the right and towards the top
of the periodic table. The thick diagonal zigzag black line shows
the main division between metals on the left of the periodic
table and nonmetals on the right of the periodic table.
However, note that the metallic elements and nonmetallic
elements adjacent to this zigzag line can show a 'mixture' of
DMITRI MENDELEEV'S PERIODIC TABLE
Mendeleev arranged the elements, known at that time, in a
periodic table by using properties of these elements and
their compounds. Mendeleev used his table to predict the
existence and properties of some elements not then
discovered. However, Mendeleev had arranged elements in
order of increasing relative atomic mass but this didn't
always give the correct order in the periodic table because of
the relative abundance of isotopes of some pairs of
elements in the periodic table…read more
Mendeleev laid out all the known elements in order of 'atomic
weight' (what we now call relative atomic mass) except for
several examples like tellurium (Te) and iodine (I) whose order
he reversed because chemically they seemed to be in the
wrong vertical column.
He arranged similar elements into vertical columns (we now
call groups) and switched to the next row (we now
call periods) when the next similar element appeared when
laid out in atomic number (left to right and then down).
He wrote out all the known properties of at least 50 elements
and looked for deeper and more meaningful patterns than his
predecessors like Newland.
He recognised that even more elements could be fitted into
groups of elements with similar properties, and these he
arranged as vertical columns, which we now call groups (of the
periodic table).…read more
In Mendeleev's periodic table the Group 1 metals (Li, Na, K, Rb) and
Group 2 metals (Be, Mg, Ca, Sr) are all in place in columns 1 and 2,
three of group 3 (B, Al, In), three of group 4 (C, Si, Sn) in place, 4 of
group 5 (N, P, As, Sb), 4 of group 6 (O, S, Se, Te), 4 of group 7 (F, Cl,
Br, I), but his group 8 (where group 0 Noble Gases are) are metals
from the first and second transition metals series.
He left gaps between elements, he reasoned from the patterns of
physical and chemical properties of similar elements of a
'group' that there must be one or more elements missing from the
Similar properties would involve physical properties like melting
point, boiling point, density, appearance and chemical properties
would include formula of compounds like oxides, chlorides etc.
Therefore, where he thought elements were missing, he not only
predicted their existence, he also predicted some of the physical
properties like melting point and density, and chemical properties
such as the formula of the oxide.
He predicted the existence of gallium (in group 3) and germanium
(he called it ekasilicon, because he expected to have much in
common with silicon in Group 4).…read more