This is the modern periodic table. 
118 elements are arranged
in the periodic table in a very
systematic manner. There's some properties
related to these elements which define the 
ways in which these elements react.
Since the elements are arranged in a very well
organized manner these properties also
follow some particular trends.
Let's see how.
One important property related to the
elements is their metallic character.
We know metals are those which can easily
remove electrons to form the positive
ions.
So in the metals,
sodium it has 2,8,1 electrons. So it can
easily lose the last electron to complete
its octet, it looses one electron so it has a stable   
electronic configuration 2,8. 
Similarly magnesium 
has electronic configuration 2,8,2 it
loses
the two electrons and forms a stable
electronic configuration 2,8,
that's forming a positive Mg2+ ion.
So metallic character 
is the ease with which the atoms lose
their electrons.
How does metallic character vary in a periodic table?
Lets see. So we remember that atomic size
decreases
when we move from left to right in a period 
and the atomic size
increases when we move from top to bottom
in a group. So what happens in a period?
We know that the atomic size is decreasing
since the atomic size
decreases 
the outer most shell is very close to the
nucleus.
So to remove an electron becomes very
difficult because
the nucleus is exerting a very great pull
on the outer most
electrons and therefore the ease to
remove the electrons decreases
and thus the metallic character decreases.
Since the metallic character decreases
the non-metallic character increases across a period.
Let's try to explain this once again. So 
we know from left to right
in a period the atomic number increases.
Since the atomic number increases
the nuclear charge also increases from
moving left to right
in a period.
This increase in nuclear charge tends to bring
the outer most shell
close to the nucleus. Hence the atomic size 
decreases. 
As the atomic size decreases the
electrons are held
very tightly to the nucleus and
therefore the ease to remove these
electrons
decreases. Since the ease to remove them
decreases
so the metallic character from moving from
left to right
in a period also decreases.
Ok, so now we have to move down the group
in a 
periodic table.
Down a group we know that atomic size
increases.
The atomic size increases because of the
increased
number of shells which overweigh the 
increased nuclear charge.
Metallic character we know is the ease to
lose the electrons.
As the size increases the outermost
electrons
are away from the nucleus, therefore the
ease to remove this outermost electron
increases. 
As the ease to remove these electrons
increase
so the metallic character increases
and so
the non-metallic character on moving from
top to bottom in a group decreases.
So what happens in a group? Let's
revisit. Nuclear charge
on moving from top to bottom in a group
increases.
As the nuclear charge increases in a
group we also know that the number of
shells
increase successively. This increase in
the number of shells
overweigh the increased nuclear
charge. The effect
of the increased nuclear charge is that it
tends to pull the electrons close to
itself 
but the number of shells increasing
overweigh the increased nuclear charge
and so the atomic size on moving from top
to bottom in a group increases.
This increase in the atomic size leads to
the fact that the electrons are 
held loosely.
Because the distance between the nucleus
and the outer most shell increases
so the electrons are held loosely hence the
ease to remove them or to lose the
electrons also increases
and so the metallic character from
moving
top to bottom in a group increases.
So there are 3 elements: Boron, Aluminium and Gallium. 
The one with the greatest metallic character is.
Lets see where do they lie in the
periodic table.
We have Boron, Aluminium and Gallium.
They lie in one group. We just studied
that on moving from top to bottom in a
group
the metallic character increases and so
on moving from top to bottom in a group
the metallic character increases,
so Gallium has the greatest metallic
character out of these three elements.
So in a periodic table when we move from left
to right
in a period the atomic size decreases due to the
decrease in the atomic size the ease to
remove the electrons also decreases and
so the metallic character decreases.
When we move from top to bottom in a group
the atomic size increases this leads to
increased distance between the outer
most shell
and the nucleus so the electrons are held loosely,
they can be easily removed
and so the metallic character increases
on moving from top to bottom in a
group.
