>> host: I love
the periodic table.
No, really.
It gives me so much information
about the elements,
how they're both different
and alike,
what they're made of,
and their mass.
Once you get to know
the various parts
of the periodic table,
I bet you'll love it too.
Okay, so maybe you won't love it
as much as I do,
but it will definitely be
a useful tool
as you learn chemistry.
And speaking of learning
chemistry,
what do you know
about elements?
Did you know that all of these
items are different elements
that can be found
on the periodic table?
Chemists separate elements
into two major groups
based on their chemical
and physical properties.
These groups are metals
and non-metals.
That's a quick start.
Now, let's join our group
of students
as they explore the trends
of the periodic table.
They'll be using periodic tables
and cards that you can find
in our "Chemistry Matters"
toolkit.
The cards contain information
about the chemical and physical
properties of various elements,
but not all of the information
we know about these elements.
The cards have been created
with several unknowns,
which makes them an excellent
tool for recognizing
various characteristics
of the elements,
and understanding why
the periodic table is organized
the way it is.
You'll see what I mean
when you watch our students
perform this exercise,
and that'll help you
when you do the same.
So let's get to it.
>> professor: Look at your
periodic tables.
The periodic table's
laid out in columns,
up and down,
and rows, side to side.
Look at the far left column
and notice that each column
is numbered one through 18.
Now, start at the top left
and label each row
one through seven.
To become more familiar
with the Periodic Table,
you'll become Dmitri Mendeleev,
the father of the Periodic Table
and one of my personal heroes.
I love Mendeleev
because his discovery in 1869
had such a huge impact
on the world of chemistry.
>> student: Isn't he the guy
who grew all of the pea plants?
>> professor: No, You're
thinking of Gregor Mendel.
He studied the variation
in pea plants,
and is known as the Father
of Modern Genetics.
Mendeleev studied the different
characteristics of the elements
that were known in his time.
On these cards you'll find
information about
the physical and chemical
properties of many elements.
Your task is to group
these elements in some way,
and use the resulting
information to identify
some unknowns.
The unknown elements
can be found in groups
or columns 1, 2, 11,
13, 14, 17, & 18.
Work together,
because you'll have lots
of information to consider.
Go 'head and pour them out
and look at your cards.
Looking at the cards,
how can you organize
all of this information?
>> student: We could group them
by a property,
like a physical state.
>> student: But most of them
are solids.
Physical state
won't separate them enough.
>> student: What if we laid them
all out,
like the Periodic Table?
>> student: Let's try that.
>> professor: Sounds like
you have a plan.
This activity is challenging
and can be very frustrating.
You'll have lots
of information to consider.
I'll let you get started
and check back in with you soon.
Okay, let's see
where you are now.
Has anyone identified
an unknown?
>> student: We've got unknowns
two and four.
Two is fluorine
and four is krypton.
>> professor: Why did you start
with those unknowns?
>> student: These unknowns
are gases.
All of the other unknowns,
and most of the knowns,
are solids.
So, we thought it'd be easier
to start there.
>> professor: Okay, so how did
you decide
on fluorine and krypton?
>> student: We looked at
the properties on the different
gas cards and put the unknown
where it fit best.
>> student: Unknown number two
is a pale yellow gas
and has a melting point
of -219.6 degrees Celsius.
>> student: The next element,
chlorine,
is a greenish yellow gas
and has a melting point
of -101 degrees Celsius.
As you keep going down
the column,
the melting point increases.
>> student: The densities
increase as you
move down the columns, too.
>> professor: Does that mean you
all agree
that unknown number two
is fluorine?
What about unknown number four?
>> student: We got fluorine too,
but we haven't gotten to unknown
number four.
We decided to do them all
in order.
>> student: We think
unknown number one
is either silicon or germanium,
because it has properties
of carbon, tin, and lead,
but we aren't sure which.
>> student: We think unknown
number three is rubidium
because its color, density,
and reactivity to water
fits in with all the other
alkali metals.
>> professor: Great work.
I really like that you guys
had multiple reasons
for each identification
that you made.
Use this information
as you keep working.
>> student: Wait a second.
You're not going to tell us
if we're right?
>> professor: No, I'm not.
Your group needs
to keep working together,
using the evidence to identify
all of the unknowns.
You can do it!
>> host: Our teacher
wasn't kidding.
This can be challenging.
But I'll figure it out.
The important thing
to take away from this
is that the Periodic Table
organizes the different elements
based on properties,
and these properties relate
to the structure of
the different atoms themselves.
You can also use these
properties to predict
element behavior.
Dmitri Mendeleev did that
when he organized
his periodic table.
He listed out properties
of elements that scientists
didn't even know existed,
which is pretty amazing
when you think about it.
So let's get back
to our classroom
to learn a little more.
>> professor: Now that you
have an idea
of the property of elements
and how they're represented
on the periodic table,
we're gonna put this
information to use.
Let's turn to the periodic table
and identify some of these
characteristics.
You should have already
numbered the rows,
also known as periods,
and the columns,
also known as groups,
on your periodic table.
Now find boron.
It's represented
by the letter B.
Does your periodic table
have a stair line
that steps down from boron
and continues until polonium,
which is Po?
If it doesn't, draw one now
using this periodic table
as your guide.
The elements to the right side
of the stairs are known
as the non-metals.
All of the elements to the left
side of the stairs are metals.
And the elements that touch
the stairs are known as
metalloids.
Let's start with the metals.
What are some
of their properties?
>> student: They're shiny.
>> professor: Okay, What's
another word we can use
for shiny?
>> student: They have luster.
>> professor: Right, luster,
good.
What else?
>> student: They're malleable
and conductive.
>> professor: Please,
explain what you mean.
>> student: Well, malleable
means that it can be shaped,
and conductive means
that electricity or heat
will flow through it.
>> professor: Good.
You might be thinking of silver
or gold, or even titanium
and copper as examples
of metals.
All of these metals are solids,
they're shiny,
they can conduct electricity,
and can be shaped
into different forms,
like statues or jewelry.
These are known as
transition metals.
Find column three
on your periodic table.
Start with column three
and count 10 columns
over to column 12.
These 10 columns make up
the transition metals.
Lightly color each of these
columns in one single color.
Okay, look at the bottom
of your periodic table.
Do you see those two rows
that look like
they were forgotten?
These are called the Lanthanide
and Actinide series
because they start with
lanthanum and actinium.
Lightly color each row
in another different color.
Most metals
conduct electricity well.
Think about your element cards.
What other elements
from the activity
were good conductors
besides the transition metals?
>> student: Sodium.
But is that a metal?
>> student: How about calcium?
That's found in your bones
so it can't be metal.
>> professor: You might be
surprised to learn that both
sodium and calcium are metals.
Sodium's in the first column.
And this column, or family,
is called the alkali metals.
Chemists call the group
or column a family,
because they have
similar properties.
Although hydrogen
is in this column,
it's not an alkali metal.
Calcium is in the second column,
which is known as the alkaline
earth metals.
Do you remember some
of the other properties
of these groups
from the Mendeleev activity?
>> student: They're not shiny
like the other metals
>> student: They're soft?
>> professor: Good, so these
metals aren't as shiny
as the transition metals
and they're much softer.
We don't make jewelry or statues
out of this kind of metal.
Go ahead and color the alkali
metals one color,
but don't color hydrogen,
and the alkaline earth metals
another color.
Hydrogen is placed
in the first column
because it's electron
is arranged similarly
to the alkali metals,
but its other properties
are more like non-metals.
Remember, non-metals
are on the right side
of the stair step line.
Color hydrogen a color
different from the alkali metals
to help remember
these different properties.
>> host: You might have been as
surprised as our students were
to learn that
not all metals are the kind
that we naturally think of
in our everyday lives.
In fact, many of these metals,
such as sodium and calcium,
are found in our bodies,
and even in the foods we eat.
In addition to all these metals,
we know that there's another
large group of elements
on the periodic table
we've yet to explore.
So let's check back in
with our students
and see what they're learning
about non-metals.
>> professor: Two special groups
of non-metals are the halogens
and the noble gases.
Hydrogen has properties
similar to the halogens,
which are in column 17.
These non-metals
are very reactive.
Column 18, the Noble gases,
they are not reactive at all.
Pick new colors and color
columns 17 and 18 now.
Look at the stair line
we talked about earlier.
Do you see the elements
whose edges make up
the stair line?
These elements
are known as metalloids
because they have properties
of both metals and non-metals.
Silicon is a well-known example
because of its use
in microchips for computers.
It's the properties
of elements like silicon
that make objects in our
everyday life possible.
Could you imagine a life
without your cell phones
or computers?
>> student: Ugh, I'd rather not.
>> professor: That's what we'd
have if we didn't know
the property of elements and how
to use them to our advantage.
>> host: The activity our
students just completed
shows us how the properties
of elements were used
to arrange the periodic table
and how the periodic table
classifies elements
into the major groups.
Now let's look at
the information
on the Periodic Table relating
to each specific element.
Do you see that each element
is in its own box?
There's a lot of information
in those boxes
that will be important
as we move throughout this,
and any other chemistry class.
So, it'll help you to understand
a few of the items
in these boxes,
as well as some related terms
before going back
to the classroom.
For instance, each element
has its own atomic number,
which represents
the number of protons
in the nucleus of an atom.
Each box on the periodic table
also contains a number
representing the elements
average atomic mass,
which is measured in
atomic mass units,
commonly referred to as AMU.
Average atomic mass
is a weighted average
of all the isotopes
of that element in the universe.
And now is a good time
to introduce the term, isotope.
An isotope is the same element
with different numbers
of neutrons.
That's right, the number
of neutrons present in atoms
of a particular element can be
different from atom to atom,
and this leads to
a lot of additional changes
in characteristics
we'll explore in later units.
Getting back now
to atomic mass units,
you'll notice that most of these
numbers have decimal values,
and you may be wondering why.
It's because not all atoms
of a particular element
are created equal.
As an example, take boron.
Let's pretend for a moment
that there are only
five boron atoms
in the entire universe.
All five of those boron atoms
have five protons
in their nuclei.
That's what makes boron, boron.
But let's say four
of the five boron atoms
have six neutrons
in their nuclei.
Those four atoms would have
a mass of 11 AMUs each,
but one of the five boron atoms
still has five neutrons
in its nucleus, which means
that atoms mass is ten.
So if we wanted to find
the average atomic mass
of boron, we would add 11
plus 11 plus 11 plus 11
plus 10, which equals 54.
We would then divide 54 by five,
and we'd get 10.8.
We could then say that boron's
average atomic mass is 10.8.
Now, most scientists
would drop the average,
and just refer to boron
by saying it has an atomic mass
of 10.811 AMU,
but it means the same thing.
As I said, we'll look at more
of these characteristics
of atoms in future units.
For now, we just wanna
get a firm understanding
of the information conveyed
in the periodic table.
So let's get back
to our classroom
to see how our students
are doing with that.
>> professor: Okay,
find hydrogen.
Do you see the number one?
Now look at helium.
It's number two.
Look at the same place
in lithium's box.
What is its number?
>> student: Lithium is three.
>> professor: Good.
These numbers are known as
the atomic numbers,
which is the number of protons
in the nucleus of the atom.
Look at lithium,
do you see the number 6.9?
There may be some other numbers
after the 9 depending on
the periodic table.
Look at beryllium and find 9.0.
Again, there might be
extra numbers.
These numbers are known as
the average atomic mass
and are measured in atomic
mass units, or AMU.
It's a weighted average
of all of the isotopes
of that element in the universe.
An isotope is the same element
with different numbers
of neutrons,
which causes it to have
different masses.
Let's look back at beryllium
on your periodic table
and figure out what other
information can be found there.
What do you see in
beryllium's box?
>> student: The letters B-e.
>> professor: Right.
B-e is the element's symbol.
Chemists often use symbols
in place of the name.
Symbols are case sensitive,
like passwords.
Beryllium's symbol
is not capital B-capital E.
The "e" is lower case.
Find argon
on your periodic table.
What's its atomic number?
>> student: Eighteen?
>> professor: Eighteen is right!
So, what is its average
atomic mass?
>> student: It's 39.9.
>> professor: 39.9 AMU.
Don't forget your units!
To what group or family
does argon belong?
>> student: Argon is on the far
right, so it's a non-metal.
>> professor: Yes,
argon's a non-metal,
but what family is that?
Remember we just color-coded
them a few minutes ago.
>> student: Is it a noble gas?
>> professor: Good, Noble gas.
Great job.
>> host: You've seen how much
information is available
to you just looking
at the periodic table.
And some periodic tables
contain even more information.
Use the key on your
periodic table to help you
understand any
added information.
You may not love
the periodic table
as much as I do yet,
but you'll be using it a lot
so you'd better make friends
with it at the very least,
as we continue to explore
the properties of atoms.
♪♪