Download Atomic Math Powerpoint - Parkway C-2

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-
for…
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 X
7
14 X
7
14 X
6
12 X
6
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
A charge atom is known as an ION
19 X-1
9
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