When Atoms
Change…
What we KNOW…
• Atoms on the periodic table are neutral.
• Atoms are neutral because they have the
same number of protons as electrons.
• protons
have a positive charge.
• neutrons
• electrons
have no charge.
have a negative charge.
What we Also need to KNOW…
• The identity of an atom is determined
ONLY by the number of protons.
• For example… If I tell you there is an
atom with 3 protons… you know it’s a
Lithium atom.
• What about 8 protons, 13 protons, 79
protons???
What happens if the number of
neutrons change???
If an atom gains Neutrons…
1. The mass increases by 1 for every neutron added.
2. The charge remains neutral. (Neutrons don’t have a
charge.)
3. The number of protons and electrons stay the same.
If an atom loses Neutrons…
1.
The mass decreases by 1 for every neutron taken
away.
2. The charge remains neutral. (Neutrons don’t have a
charge.)
3. The number of protons and electrons stay the same.
What happens if the number of
neutrons change???
If an atom gains Neutrons…
1. The mass increases by 1 for every neutron added.
2. The charge remains neutral. (Neutrons don’t have a
charge.)
3. The number of protons and electrons stay the same.
If an atom loses Neutrons…
1. The mass decreases by 1 for every neutron taken
away.
2. The charge remains neutral. (Neutrons don’t have a
charge.)
3. The number of protons and electrons stay the same.
The atom is now called an
ISOTOPE!
When atoms gain or lose neutrons!
ISOTOPE EXAMPLE
Hydrogen Atom
Has a mass of 1
and an atomic
number of 1
Hydrogen Isotope
Has a mass of 2
and an atomic
number of 1
ISOTOPE NOTATION
We communicate that we have an
isotope by using the Atomic Symbol of
the isotope followed by the “NEW”
mass number.
ISOTOPE NOTATION Li-7
Ex: An Isotope of Lithium is:
Li - 6
Isotope INVENTORY
Completing a particle inventory for an
Isotope is almost the same as the
neutral atom EXCEPT we USE THE
“NEW” MASS NUMBER to calculate
neutrons.
Ex: Li-6
3p+ (since it’s Lithium!!!)
3e- (since they are still equal to p+)
3n
Isotope Practice
• Ca atom has a mass of 40.
• The isotopes for Ca are:
•
Ca-42, Ca-43,Ca-44, Ca-46, & Ca-48.
• 1.) How many neutrons are in a Ca atom
and each of its isotopes?
2.) What are the differences and
similarities between the Ca atom and its
isotopes?
Isotope Practice
Ca atom has a mass of 40. (atomic # =20)
The isotopes for Ca have masses of 42,43,44,46, & 48.
1.) How many neutrons are in a Ca atom and each of its
isotopes?
(Ca ATOM: 40 – 20 = 20n)
(ISOTOPES: 42-20=22n, 43-20=23n, 44-20=24n,
46-20=26n, 48-20=28n)
2.) What are the differences and similarities between the
Ca atom and its isotopes?
Similarities
(All have 20 p+ all have 20 eall neutral
all are Calcium)
Differences
(The # of neutrons is different,
masses are all different.)
The Atom Building Game
•
•
•
•
•
Everyone gets 7 blue, 7 red, 7 yellow
Red = Protons
Blue = Neutrons
Yellow = Electrons
Play 1-5 marbles per turn.
Number of neutrons and protons
Subtract the two to find the
number of neutrons
Number of protons and electrons
Everyday Uses of Isotopes
Smoke Detectors and Americium-241
What most consumers don't know is that many
of these units contain a small amount of
americium-241. By utilizing the radioactive
properties of this material, smoke from a fire
can be detected at a very early stage. This early
warning capability has saved many lives. In fact,
studies have shown that 80% of fire injuries and
80% of fire fatalities occur in homes without
smoke detectors.
Carbon-14 Dating
Recalling that all biologic organisms contain a given
concentration of carbon-14, we can use this
information to help solve questions about when the
organism died. When an organism dies it has a
specific ratio by mass of carbon-14 to carbon-12
incorporated in the cells of it's body. At the moment
of death, no new carbon-14 containing molecules are
metabolized, therefore the ratio is at a maximum.
After death, the carbon-14 to carbon-12 ratio
begins to decrease because carbon-14 is decaying
away at a constant and predictable rate.
Remembering that the half-life of carbon-14 is 5700
years, then after 5700 years half as much carbon-14
remains within the organism.
Food Irradiation
Food irradiated by exposing it to the gamma rays
of a radioisotope -- one that is widely used is
cobalt-60.
The gamma rays pass through the food to destroy
many disease-causing bacteria as well as those that
cause food to spoil. It’s not strong enough to
change the quality, flavor or texture of the food.
The food never comes in contact with the
radioisotope and is never at risk of becoming
radioactive!
Reviewing Isotopes
What are isotopes gaining or losing?
Neutrons!
Here is an Atom of Oxygen (how many neutrons?)
Atomic Mass=16
8 neutrons
These are isotopes of Oxygen
O-17
O-18
9N
10N
So…How many neutrons does each
isotope of Oxygen NOW have?
Isotope Practice
1.)How many neutrons are in each of Zinc’s
isotopes? Zn-65
Zn-64____ Zn-67_____ Zn-70____
2.) What are the differences and
similarities between the Zn atom and its
isotopes? Set-up a “T” Chart
Isotope Practice
1.)How many neutrons are in each of Zinc’s
isotopes? Zn-65
34 Zn-67_____
37 Zn-70____
40
Zn-64____
2.) What are the differences and similarities
between the Zn atom and its isotopes?
Similarities
• All have 30 p+ all have 30 e• all neutral
• all are Zinc
Differences
• # of neutrons is different
• masses are all different
Isotope Warm up
1.)How many neutrons are in each of
Strontium’s isotopes?
Sr-84____ Sr-86_____ Sr-87____
Answers:
Sr-84 46
Sr-86 48
Sr-87 49
Quiz Quick
Isotopes gain or lose…
A.
B.
C.
D.
electrons
protons
neutrons
nuclei
When an atom gains neutrons,
its charge changes.
A. True
B. False
When an atom gains neutrons, the number
of protons and electrons do not change.
A. True
B. False
The only subatomic particles
that never change are…
A.
B.
C.
D.
Valance electrons
Protons
Electrons
Neutrons
What happens if the number of
electrons change???
If an atom gains electrons…
1. The charge becomes negative. (There are more
negative e- than positive p+ now!)
2. The mass stays the same (electron’s mass = 0).
3. The number of protons and neutrons stays the same.
If an atom loses electrons…
1.
The charge becomes positive. (There are less
negative e- than positive p+ now!)
2. The mass stays the same (electron’s mass =0).
3. The number of protons and neutrons stays the same.
What happens if the number of
electrons change???
If an atom gains electrons…
1. The charge becomes negative. (There are more
negative e- than positive p+ now!)
2. The mass stays the same (electron’s mass = 0).
3. The number of protons and neutrons stays the same.
If an atom loses electrons…
1. The charge becomes positive. (There are less
negative e- than positive p+ now!)
2. The mass stays the same (electron’s mass =0).
3. The number of protons and neutrons stays the same.
The atom is now called
an ION!!!
When atoms gain or lose electrons!
*Ions are charged particles!
Ions form so that unstable atoms can
bond with other unstable elements to
become a stable substance!
Charged Ions
Anion (-) Negatively charged ion.
Cation (+) Positively charged ion
Quick Quiz
If an atom loses electrons, its
mass changes?
A. True
B. False
Ions gain or lose…
A.
B.
C.
D.
isotopes
protons
neutrons
electrons
Gaining electrons causes atoms to…
A.
B.
C.
D.
Gain more mass
Have a charge
Stay neutral
Lose mass
ION EXAMPLE
H+ is a
positive
hydrogen
ION
H: Is the
neutral
hydrogen
atom
H- : is a
negative
hydrogen
ION
Ion Practice
Na
Be
I
Ca
Sb
S
P
C
Na+1
Be+2
I-1
Ca+2
Sb-3
S-2
P-3
C+/-4
Ion Worksheet Answers
Li
+1
K
Br
-1
Ba
+2
Mg
+2
Te
-2
B+3
Sn
-4
F
-1
As
-3
N
-3
Cl
-1
Si
O
+1
+/-4
-2
Al+3
Ion Worksheet Coloring
Li
+1
K
Br
-1
Ba
+2
Mg
+2
Te
-2
B+3
Sn
-4
F
-1
As
-3
N
-3
Cl
-1
Si
O
+1
+/-4
-2
Al+3
What patterns did you notice from
coloring your ions on the periodic table?
*hint* there is more than one!
•
•
•
•
•
•
The families where the same color.
The families had the same ionic charge.
Metals have a positive charge.
Non-metals have a negative charge.
Metals lose electrons.
Non-metals gain electrons.
Practice
Draw the Bohr
models for the
following elements
and find the ionic
charges for each.
Rb
+2
Sr
-3
Bi
+1
Rb
Sr
Bi
How is the neutral(no charge) atom Se
and it’s isotope Se-78 similar and
different?
(Set up a “T” chart)
Similar
Different
Same element
Different masses
Same # of protons
Different # of neutrons
Same # of electrons
Same charges
How are isotopes and ions similar and
different? (setup a T chart)
(hint* think about particles, masses and charges)
Similarities
Same number of
protons only!
Differences
Diff Masses
Diff Number of
neutrons
Diff Charges
Diff Number of
electrons
Practice
Draw the Bohr
models for the
following elements
and find the ionic
charges for each.
Ga
+2
Sr
-4
Pb
-5
Ga
Sr
Pb
Patterns on
the
Periodic Table
+1
+2
Ionic
Charges
0
+3 +/-4 -3 -2 -1
Valence
Electrons
Energy Shells of Atoms
1 Shell
2 Shells
Period 1
Period 2
3 Shells
Period 3
4 Shells
Period 4
5 Shells
Period 5
6 Shells
Period 6
7 Shells
Period 7
Families/Groups have a lot
in common…
• We now know that elements in a group all
have the same # of valence e-.
• We also now know they all form ions with
the same charge.
• But…there are a lot of other properties
that elements in a family also share!
• Such as…Atomic Width, Ionization Energy,
Electronegativity and reactivity.
Atomic Radius (Width)
• Atomic radius is simply the radius (width) of the
atom, an indication of the atom's volume.
• Periods - atomic radius decreases as you go from
left to right across a period.
• Why?
• Stronger attractive forces in atoms (as you go
from left to right) between the opposite charges in
the nucleus and electron cloud cause the atom to be
'sucked' together a little tighter.
• Largest atomic species are those found in the SW
corner of the periodic table.
Atomic Radius (Width)
• Groups - atomic radius increases as you
go down a group.
• Why?
• There is a significant jump in the size
of the nucleus (protons + neutrons) each
time you move from period to period
down a group. Additionally, new energy
levels of elections clouds are added to
the atom as you move from period to
period down a group, making the each
atom significantly more massive, both is
mass and volume.
Ionization Energy
• Ionization energy is the amount of energy
required to remove the outmost electron. It
is closely related to electronegativity.
• Group - ionization energy decreases as you go
down a group.
• Why?
• The shielding affect makes it easier to
remove the outer most electrons from those
atoms that have many electrons (those near
the bottom of the chart).
Electronegativity
• Electronegativity is an atom's 'desire' to grab
another atom's electrons.
• Period - electronegativity increases as you go
from left to right across a period.
• Why?
• Elements on the left of the period table have 1 2 valence electrons and would rather give those
few valence electrons away, as a result, they
have low electronegativity.
• Elements on the right side of the period table
only need a few electrons, so they have strong
desire to grab another atom's electrons.
Electronegativity
• Electronegativity is an atom's 'desire' to grab
another atom's electrons.
• Group - electronegativity decreases as you go
down a group.
• Why?
• Elements near the top of the period table have
few electrons to begin with; every electron is a
big deal. They have a stronger desire to acquire
more electrons. Elements near the bottom of
the chart have so many electrons that loosing or
acquiring an electron is not as big a deal.
Reactivity
• Elements become more reactive as you go
down a group on the left side
• And more reactive as you go up a group on
the right side!
• Reactivity refers to how likely or vigorously an
atom is to react with other substances.
• Based on this, where are the most reactive
elements found on the periodic table?
Bottom left corner (Fr) and top right corner (F)
What are (7) things you can now predict
about the element Iodine (I), based on
where it is located on the Periodic Table?
1.
2.
3.
4.
5.
6.
7.
It has 7 valence electrons
It has 5 energy rings/shells
It is a non-metal
It’s gaining 1 electron
It’s ionic charge is -1
Less reactive than Br and Cl
But it’s more massive than Br and Cl
Properties of Non-metals
•
•
•
•
No luster
(dull)
Brittle
Not ductile (breaks easily)
Not malleable
What can you now tell me about the
element Nitrogen (N) and Potassium (K),
based on where they are located on the
Periodic Table?
(think about shells, valence e’s, charges, metal/non-metal, gaining/losing e’s)
•
•
•
•
•
Nitrogen
Potassium
•5 valence electrons
1 valence electron
It has 4 energy rings •It has 2 energy rings
•It is a non-metal
It is a metal
•It’s gaining 2 electrons
It’s losing 1 electron •It’s ionic charge is -3
It’s ionic charge is +1
You are the bus driver. At your first
stop, you pick up 29 people. On your
second stop, 18 of those 29 people get
off, and at the same time 10 new
passengers arrive. At your next stop, 3
of those 10 passengers get off, and 13
new passengers come on. On your fourth
stop 4 of the remaining 10 passengers
get off, 6 of those new 13 passengers
get off as well, then 17 new passengers
get on. What is the color of the bus
driver's eyes?