We are going to look at group 1 as an example
of the pattern you can see in the periodic
table. Group 1 contains the elements Lithium,
Sodium, Potassium, Rubidium, Caesium and Francium.
If you draw out their electronic structure
the first thing you notice is they all have
one electron in their outer shell. The other
thing to see is the number of shells they
have is related to the row they're in on
the periodic table. For example Sodium has
three, so this therefore is their period.
The elements in the group are all metals,
they're all soft metals which can be easily
cut. They get softer as you go down the group,
not that you'd be wise to cut Rubidium and
Caesium. All of the elements are stored in
containers that either have paraffin or inert
gases in. This is because of their reactivity,
all the metals will react with air readily.
They tarnish quickly in air, reacting quicker
as you go down the group. Their reaction with
water is violent and shows the same trend.
Why is this? Two reasons. Firstly, the outer
electron they have is easily lost. Secondly,
as the atom gets bigger, they find it increasingly
easy to lose the electron. This is why Caesium
is the most reactive metal we know. The reason
for this is the outer electron is a long way
away from the nucleus and therefore is easily
picked off but also the electrons in the other
shells interfere and stop the nucleus holding
on to the electron. This concept is known
as shielding. This acts a bit like wrapping
a magnet in paper and imagining that you're
trying to use it to pick up nails, the more
paper there is, the less nails the magnet
will attract.
