Subatomic Particles in an atom!
• 3 main particles in the atom:
• Neutrons
• Protons
• Electrons
LOCATION
e-
In physics, we will learn that even
these particles are made of smaller
particles!
SIZE
p+
n
Remember, most of an atom is
empty space!
• An atomic model the size of
Busch Stadium and parking
would contain a pea sized
nucleus containing 95.95% of
the atoms mass.
• The pea at the pitcher’s
mound would be the nucleus,
and an ant crawling on the
parking lot outside would be
an electron!
• That is how much empty
space is in an atom, and how
tiny electrons are compared
to the nucleus!
Electrons
• Discovered by JJ Thompson, RA
Millikan
• Located around nucleus
• Negatively (-) charged particles
• Mass = essentially zero - only 1/2000 of a
proton or neutron
• Charge = -1
• Occupies the majority of space in an atom,
but contributes NOTHING to the mass of an
atom!
e-
Protons
• Eugen Goldstein (1886)
•
•
•
•
•
Located in….
The tiny, dense nucleus!
Mass of 1.67 x 10-24 grams
We call that 1 amu, or a mass of 1
Charge = +1
p+
Neutrons
• James Chadwick (1932)
•
•
•
•
•
Located in….
The tiny, dense nucleus!
Mass of 1.67 x 10-24 grams
We call that 1 amu, or a mass of 1
Charge = 0
n
Nuclear Symbols
X = element symbol
Z = mass number
= # protons + #
neutrons
A = atomic number
= # protons
(gives an element its
identity!!)
So… # neutrons = Z-A
Z
X
A
charge
Atomic Number
•
•
•
•
•
•
•
Number of protons
Number on bottom of symbol
Gives an atom its identity!
If 6 p+ in nucleus, the atom is….
Carbon!
It 7 p+ in nucleus, the atom is….
Nitrogen!
14
7
12
N
C
6
Mass Number
•
•
•
•
•
•
•
•
•
•
•
•
Mass Number = number of protons + number of neutrons
Number on the top of the symbol
It tells you the mass of atom!
Not all atoms of the same element weigh the same!
Two atoms of Carbon are shown below. One weighs 12, one
weighs 14.
If they are both Carbon, the must both have the same number
of…..
Protons! Each has…..
6 protons!
So different numbers of….
Neutrons!
How many neutrons
does each have? How would
we figure that out?
Mass Number - Atomic Number =
Number of neutrons
12
14
C
C
6
6
6 neutrons!
8 neutrons!
ISOTOPES
• Atoms with same # Protons, but different #
neutrons
• Example– 35Cl and 37Cl are isotopes of chlorine
• They only differ in their…..
• Mass!
• They both have how many protons….?
• 17!
• Look at the periodic table, though - the periodic
table lists the AVERAGE ATOMIC MASS
• For chlorine, it is 35.453 amu. This doesn’t look
like an average between 35 and 37!
• That is because they don’t exist in nature 50-50!
• Chlorine-35 makes up 75.77% of all Chlorine
atoms in the universe
• Chlorine-37 makes up 24.23% of all Chlorine
atoms in the universe
Electrons and atom charge
• If # p+ = # e• Then atom is NOT
CHARGED
• If #p > #e• Then + charged
(cation)
• Charge = #p+ - #e• If # p < # e• Then – charged
(anion)
•ALL ELEMENTS ARE NEUTRAL, AND NOT CHARGED - AN
ELEMENT HAS TO REACT IN ORDER TO BE CHARGED!
•A CHARGED ATOM IS CALLED AN ION
•A NEGATIVE ION IS CALLED AN ANION, AND A POSITIVE ION
IS CALLED A CATION
How many
108
Ag
47
+
p,
n,
e
41
20
??
+2
Ca
47
p+ = 20
= 47
e- = 18
n = 61
n = 21
Charge on atom…. 0
Charge on atom…. +2
p+ =
e-
Write the nuclear symbol for…
• An atom containing 18 e-,
16 p+, and 17 n.
• What element is it??
• Atomic number = 16
• # p+ = 16
• Element is….
• Sulfur
• Number of electrons tells us…
• There are two more electrons
than protons
• The electrons are winning by
2!
• Charge is -2!
• Mass Number = #p+ + #n
• 16 p+ + 17 n = mass of 33
33
S
16
-2
Which of the following represent
isotopes of the same element?
16 X
8
16
7X
14
7X
14
6X
12
6X
Look for same atomic #: (same # of protons)
16 X and 14 X both have 7 protons, so are
7
7
isotopes of Nitrogen.
14 X and 12 X both have 6 protons, so are
6
6
isotopes of C.
Which of the following represent
ions?
23 X +1
11
14 X
7
19 X-1
9
A charge atom is known as an ION
Positive ions are called CATIONS
Negative ions are called ANIONS
Look for any atom with charge in the upper right hand corner
(with a + or -)
Charge means the atom has reacted, and now has either MORE electrons
than protons, or LESS electrons than protons
Atoms with – charge have GAINED electrons
Atoms with + charge have LOST electrons
The periodic table!
The periodic table!
The periodic table!
Where the element is located tells us
everything about that element!
1
2
3
4
A
B
C
5
6
7
8
•Vertical columns are
called groups…
•The number of the
group tells us how
many electrons are in
the outermost energy
ring!
1
2
3
4
5
6
7
8
•These are known as
valence electrons…
•These are the ones
that react!
A
•There are 8 main
groups…
B
C
•These groups also
have names….
•Group I = Alkali Earth
Metals
•Group II – Alkaline Earth
Metals
•Group III – Boron Group
•Group IV – Carbon Group
•Group V – Nitrogen Group
•Group VI – Oxygen Group
1
2
3
4
5
6
7
8
•Group VII – Halogen Group
•Group VIII – The Noble
Gases Group
•A = Transition metals
A
•B = Lanthanide metals
•C = Actinide metals
B
C
•B and C are collectively
known as the inner
transition or rare earth
metals
1
2
3
4
A
•Horizontal rows are called
series or periods….
•They tell us how many
energy rings or levels an
atoms has….
•There are 7 periods or
series
B
C
5
6
7
8
•How many valence electrons
does potassium have?
•How many energy levels
does potassium have?
1
2
3
4
A
•It has one valence electron –
it is in group I!
•It has four energy levels – it
is in period 4!
B
C
5
6
7
8
The octet rule…
The most important rule in chemistry
It states that all atoms will react in order to have 8
electrons in their outer energy ring!
Metals like to give electrons away to get eight, since they
only have a few valence electrons
Non-metals like to take electrons to get eight, since they
are close to having eight valence elecrons!
Notice when sodium loses the
electron in its third energy ring, it
no longer has a third energy ring,
and its outermost energy ring is
now the second, which has 8
electrons!
The octet rule…
The most important rule in
chemistry
It states that all atoms will react
in order to have 8 electrons in
their outer energy ring!
Metals like to give electrons
away to get eight, since they
only have a few valence
electrons
Non-metals like to take
electrons to get eight, since
they are close to having eight
valence elecrons!
Notice how chlorine
TAKES the electron from
sodium – it originally had
seven valence electrons,
and now it has eight!
Other atoms can bond
this way…
Which atoms are more reactive…?
Harder to take two…
It is easier to give away one
electron than to give away two!
Sodium can give away one
electron, where magnesium can
give away two!
That makes it more reactive!
Once the electron leaves, the
atom becomes positive….
It is harder, then, for magnesium
to give away a second electron….
The positive atom pulls on that
electron!
Easier to take one…
The size of the atom!
The size of the atom….
It decreases as
we go across the
periodic table…
It increases as
we go down the
periodic table…
Why….?
Protons pull on electrons!
As we go across the
periodic table, atoms get
smaller…
You are adding more
protons and electrons…
The protons attract the
electrons, making the atom
smaller!
Atoms get bigger as we go
down the periodic table…
As we go down the
periodic table, atoms have
more and more electrons!
We have to add energy
rings to make room for
more electrons!
This makes the atom get
bigger!
Lithium
2e 3 p+
1e 1p+
1e 8e 8e -
Sodium
2e -
1e 8e 2e 11 p+
1e -
Hydrogen
Potassium
19 p+
Ionization Energy…..
Hardly any
energy - 495.8!
e-
e-
e-
e-
e-
e-
Lots of energy 1251.1!
e-
e17 p+
18 n
e-
e-
eeee-
ee-
e-
Chlorine atom
This is the energy you
need to take an outside
electron off of an atom!
What kinds of atoms
do you think it is really
TOUGH to take an
electron away from?
What kinds of atoms
do you think it is really
EASY to take an
electron away from?
Why is this….?
Ionization Energy….
It takes hardly any
energy to take an
electron from a
metal…
They want to give
them away!
They don’t have many
in their outer ring!
Only one
outer
electron!
Ionization Energy….
e-
It takes TONS of
energy to take an
electron from a nonmetal…
They don’t want to
give any away!
They have close to 8
in their outer ring!
e-
e-
e-
e-
e-
e-
e17 p+
18 n
e-
e-
eeee-
ee-
e-
Chlorine atom
7 outer
electrons close to 8!
Electronegativity….
This is the tendency to
pull on an electron in a
bond….
What kinds of atoms
do you think really pull
on electrons in a
bond?
What kinds of atoms
do you think don’t pull
on electrons in a
bond?
Chlorine atom
Why is this….?
Electronegativity….
•
EN = .93
Nonmetals have high electronegativities,
metals have low electronegativity.
EN = 3.16