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Chapter 1
Everything is made up of something
The topic of chemistry studies what
those some things are.
Chemistry studies Matter, which is
anything that has mass, and takes
up space
People used to think that the world
was made up of 4 principal building
blocks
Earth
Water
Fire
wind
Dalton
IN the 1700’s a teacher in England
began to think that everything was
up of small building blocks that we
couldn’t see.
He called these building blocks atoms
He also explained that different
materials got their differences
because they were made up of
different building blocks, or different
atoms.
But all basic building blocks (Atoms)
of the same type were exactly the
same.
Atomic Theory
His theory can be explained in 4
simple points
1.All elements are made of tiny atoms
we cant see
2.All atoms of the same elements are
identical even if they came from
different places
3- Atoms of different elements are
different. This means that the reason
gold is different then silver is
because its atoms are different.
4- Many new materials are made when
atoms of different elements mix
together, these are called
compounds.
What is an atom made of
Dalton said atoms are he smallest thing, he
was almost right.
The atom is actually made of smaller pieces
called Sub-Atomic particles.
(Sub means under, so sub atomic means under
the atom, or inside the atom)
The Electron
The first subatomic particle
discovered was the electron.
This was discovered by J.J.
Thompson he used a cathode ray
tube
He discovered that when he added a
battery to opposite ends of the tube,
it created a beam that would be
repelled by negative magnets,
And attracted to positive magnets.
(Show movie on cathode ray)
If there are negative
charges……
Once it was discovered that all atoms
have tiny particles of negative charge
(electrons) it was reasoned there
must also be positive charges.
This was needed to make the overall
atom neutral.
Where are the positive atoms
People first thought the negative
charges were embedded in the atom,
with positive charges all around them
This was called the plum pudding
model
There was a scientist named Earnest
Rutheford.
He performed an experiment to see
where the positive and negative
charges were.
He performed the Gold foil
experiment (very important)
He took radioactive material and
directed the beam of radiation
(Which had a positive charge) at a
sheet of gold foil. This beam was
called alpha particles
He also had radioactive paper behind
the gold to see where the particles
deflected.
What he found
He found that almost all of the
particles he shot at the gold went
right through, but a few were
deflected.
They were deflected a lot!
He reasoned that the positive
charges in the atom were deflecting
his radioactive alpha particles.
But 99% of his alpha particles got
through.
But the ones that were deflected
were really deflected
He deduced that the atom was
mostly empty.
This was why most alpha particles
got right through.
But the positive charges inside were
very dense.
He called these positive charges
protons,
He hypothesized they must be
clustered tightly in a small part of
the atom called the Nucleus
(show movies on gold foil
experiment)
Problem
If there were only lots of positive
charges (protons) in the nucleus
very tightly packed wouldn’t they
repel each other like magnets of the
same charge.
There must be something in the
nucleus, but in between the protons
to space them out.
It was later discovered that in fact
there were neutral particles in the
nucleus, and that they were stuck in
between the protons to space them
out.
These particles are called neutrons.
Because they have no charge, they
are neutral.
Recap
Lets re-cap what we know
Protons are +
Neutrons have no charge
They both live in the nucleus
Electrons go around the Nucleus and
have a negative charge.
Also the atom is mostly empty
space
More on electrons
Electrons can orbit the nucleus at
different distances.
The farther away an electron gets
the weaker it is held by the positive
nucleus.
This means that the farther away an
electron is the more energetic it is.
Each orbit level can hold a set
number of electrons.
The first level holds 2, the next holds
8, the next hold 18.
The rule of electrons is that electrons
must fill up a lower level before they
can fill up a higher level.
This is called Aufbau’s rule.
Valence electrons
If an atom has 11 electrons that
means it will have 2 electrons in level
#1
8 in level # 2
And 1 electron in level # 3
These electrons in the last level are
called Valence electrons
Orbitals
Electrons don’t really go around the
nucleus in a nice simple circle, even
though we draw it that way.
Electrons orbit in very complicated
ways.
The place that electrons are
likely to be found is called an
orbital
Atomic Weights
A protons and a neutron weight the
same amount.
They both weigh
.00000000000000000000000000167
grams
This number is to small and is hard
to remember.
Instead we say a proton and neutron
weigh 1 Atomic Mass Unit (AMU)
Electrons are much much much
smaller!!
Atomic number
On the periodic table we arrange
elements by the number of protons
they have.
The number of protons something
has is called it’s atomic number.
It is the bold number on the periodic
table.
Atomic number
Each & every atom of the same
element must have the same
number of protons.
Meaning they must have the same
atomic number.
Ex. If chlorine has 17 protons it must
have an atomic number of 17.
Atomic mass
The number of protons an atom has
plus the number of neutrons
something has is called the atomic
mass.
Ex. If a chlorine has 17 protons and
16 neutrons it has an atomic mass of
33.
Atomic mass
Many times we will not be told the
number of neutrons an atom has.
But if we know the atomic number
and atomic mass we can determine
the number of neutrons
Atomic mass
Determine the # of neutrons of an
oxygen atom with an atomic mass of
17.
Hint oxygen is O on the periodic
table.
Isotopes
Even though every single atom of
the same element must have the
same number of protons, they can
have different number of
neutrons.
Ex. Every carbon has 6 protons, but
some may have 6 neutrons and
some may have 7. etc.
Isotopes
If we have 2 atoms of carbon both
with 6 protons, but different
numbers of neutrons, they called
isotopes of each other.
Isotopes are atoms with the same
protons and different neutrons.
Isotope symbols
As soon as I say carbon you can
know it has 6 protons.
But you don’t automaticlly know how
many neutrons it has.
So to say a carbon with 6 neutrons
we say
Carbon-12 or C-12
The number after the symbol tells us
the atomic mass.
Examples
Find the number of Neutrons in:
C-12, C-13, & C-14
Nitrogen- 13, & Nitrogen-15
Lithium-6 & Lithium-5
Average Masses
If you take 10 tests…
If you get an 90 on 7 of them
A 55 on 1
And a 85 on 2
How can we find the average?
Average masses
Should we take the time to add them
all up and then divide by 10?
An easier way is to find the
percentages of each & multiply by
the grade.
.7 X 90=63
.1X 55=5.5
.2 X 85 =17
Then we add them all= 85.5
Isotope average
Since different atoms of the same
elements can different numers of
neutrons they will have different
Atomic masses.
How can we find the average Atomic
mass
Isotope average
We multiply the percentage an
isotope is found by its mass, then
add all those up.
Ex. If 98.89 % of all carbons are C12
& 1.108% are C 13
What is the average mass of a
Carbon.
Excitement of Electrons
We learnt that all electrons must fill
up the lower levels of energy before
filling up the higher level.
If an electron absorbs energy it can
sometime JUMP up an energy level
Excited electrons
When an Atom has an electron that
JUMPED up a level it is called an
excited Atom.
When it has only normal electrons it
is called the ground state
Example
Sodium has 11 electrons
In the ground sate its 2-8-1
In the excited state it could be 2-7-2
or 1-8-2.
Examples
Find the ground state and excited
state for Magnesium (Mg)
Excitied electrons
Excited electrons can only stay at the
higher level for a split second
After this they must fall down to the
original level
When this happens they give of their
energy as light
Bright light spectrum
Since every element is different they
will give off different color & amounts
of light when they have excited
electrons ‘Fall down”
This is called the bright light
spectrum
Types of matter
There are 3 main types of matter in
the world.
Elements, Compounds, & Mixtures
Elements
Elements are substances that cannot
be broken down smaller by chemical
means.
Gold is an element, it cant be broken
down to less then gold.
It can be broken down to smaller
atoms of gold, but you cant turn gold
into not gold
Compounds
Compounds are when 2 or more
different elements are chemically
combined in set ratios.
Ex. Carbon Dioxide CO2.
It is made of 1 carbon and 2 oxygens
NH3 (Ammonia) it is made of 1
Nitrogen and 3 hydrogen.
Compounds
Every Carbon Dioxide in the world is
made of 1 carbon and 2 oxygens.
No matter where a carbon dioxide it
is found it is always a CO2.
This is called the Law of Definite
Proportions
Compounds
Since compounds are made of 2
elements combined together they
can be chemically broken apart.
EX. NH3 can be broken down into 1
Nitrogen and 3 Hydrogen’s.
Remember
Elements can not be broken
down chemically compounds can
Which of the following cannot be
broken down.
1.Ammonia
2.Antimony
3.Phosphate
Mixtures
Mixtures are when 2 substance are
only physically mixed not chemically.
Examples
1.Salad dressing
2.Cement
3.Air
4.Chocolate milk
2 types of mixtures
There are 2 types of mixtures.
Evenly mixed & not even
Or the Same all over & not the same
Mixtures
If mixtures are even all over it is
called Homogenous Mixture
Homo = Same (homosexual wants
the same)
Ex
Chocolate milk, Coffe, Soda
Mixtures
If 2 mixtures are not mixed evenly
they are called Heterogeneous
mixtures
Hetero = different (hetero sexual
wants different)
Examples
1.Sand and water
2.Oil & water
Differences
Compounds are not similar at all to
the elements they are made out of
NaCl is salt. It is not poisonous
But Sodium (Na) & Chlorine (Cl) are
both poisonous by themselves
Differences
But mixtures still keep their separate
identities.
If there is a mixture of salt & water
they both keep their same properties
We can use this difference to
separate them.