The periodic table helps shed light
on the characteristics of elements by grouping
them in families.
Chemical families
contain elements with similar physical and
chemical properties,
which are determined by the outermost electron
energy level,
or valence.
Often, each chemical family is color-coded,
which makes it easy to identify elements
with similar chemical and physical characteristics.
As a Periodic Table Investigator,
it is critical that you understand
to which chemical family each element belongs.
You must be able to match physical and chemical
properties
to their families.
Understanding chemical families is the second
tool in your toolkit.
And this is a good place for a real world
example, too.
A significant part of my lab
is dedicated to firearm and toolmark identification.
As they say in my business,
"Every contact leaves a trace."
And nearly every criminal uses a tool at some
point
whether it is a hammer, a screwdriver, a hacksaw,
or an explosive.
These tools leave microscopic fragments, like
fingerprints,
that can often help place a person or object
at the scene of the crime.
This may require us to determine the exact
chemical make up
of the fragments in question.
Are these iron fragments?
Nickel?
Again, it matters!
Sometimes the chemistry is what verifies that
a shard of metal found
at a robbery matches the crowbar found in
the suspect's car.
Let's take a closer look at chemical families.
The simplest way is to divide elements into
two categories:
metals and non-metals.
In chemistry,
the word "metal" does not always mean what
you might think.
For example, we all know gold and silver are
metals,
but did you know that sodium is also classified
as a metal?
The first chemical family is alkali metals,
which are found in Group 1.
Alkali metals exhibit properties similar to
other metals,
but have lower densities.
They all have one loosely bound electron
on their outer valence shell.
This gives them the largest atomic radii
of the elements in their respective periods.
For instance, potassium's atomic radius
is greater than calcium, scandium, titanium,
or any other element in Period 4.
Alkali metals also have low ionization energies,
which implies that they readily give electrons
to a reaction,
which results in their metallic traits and
high reactivities.
They also have low electronegativities,
which means they have a lower ability
to take electrons 
in 
a reaction.
