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Using the Periodic Table
6
Carbon
C
12.011 amu
• Atomic number- always a whole
number, increases in order,
represents the number of protons in
each atom
• Atomic name, often in Latin,
sometimes uses a common name,
sometimes there are disagreements
• Atomic symbol – often, but not
always, matches the name; Always
capitalize the first (only the first )
letter
• Atomic mass- the mass of the
atoms based on the average of all
the most common isotopes
Chapter 6
Atoms
• Philosophy question: If you jump half-way
across the room, and then continue
jumping half-way, how many jumps until
you reach the other side?
• Aristotle, the famous Greek
philosopher and scientist, argued
that a substance could be divided
again and again, forever getting
smaller and smaller pieces
• During his time people believed
the universe was made of four
elements; fire, water, earth and
air.
• The idea of “uncuttable” particles was first
suggested by Democritus around 440 B.C.
• “Atomos” means indivisible
Antoine Lavoisier
• Considered the Father of
Chemistry due his
extensive research and
many experiments,
including how things burn
(food, wood etc) and the
Law of Conservation of
Mass
• Executed in 1794 during
the French revolution
Section 1 Atomic Theory
• Atomic Theory (by John
Dalton) published in 1803
– All substances are made
from atoms. Atoms cannot
be created, divided or
destroyed.
– Atoms of the same element
are exactly alike.
– Atoms can join together to
form new substances.
Parts of the Atom
Particle
Charge
Location
Size
Proton
Positive
In the nucleus
1 a.m.u.
Neutron
No charge
(neutral)
In the nucleus
Almost 1
a.m.u.
Negative
Outside the nucleus,
orbiting at nearly the
speed of light
Very tiny,
1/1000th
a.m.u.
Electron
Structure of the Atom
• Protons
+
– Positively charged
– Found in the nucleus of the
atom (center)
– Mass of 1 amu (atomic mass
unit)
– Gives the element its atomic
number on the periodic table
• #1 (hydrogen) has 1 proton
• #4 (beryllium) has 4 protons
Protrons were discovered by
Ernest Rutherford in 1911 and
he discovered the empty space
within an atom in 1909
• Neutrons
– Neutral charge ( no
charge)
– Found in the nucleus
(center)
– Mass slightly smaller
than a proton, still
considered 1 amu
– Protons + Neutrons @
atomic mass (rounded
to the nearest whole
number)
N
Electron
• Electrons
– Negatively charged
particles
– Found outside the nucleus,
moving at nearly the speed
of light, in specific levels
– Most commonly atoms are
neutral particles having
equal numbers of protons
and electrons
– Very small ( about 1/1000th
of a proton)
Electrons were discovered by
J.J. Thompson in 1897
Proton
Neutron
* In 1913 Niels Bohr suggested that electrons
travel in specific paths called Electron Shells
• Each level can only
contain a certain
number of electrons
before it is full
• Each level will fill
completely before
electrons go to the
next level
• Lower levels fill first
• Isotope
Hydrogen (H-1), most
common 99.9%
– Atoms can often be found
with different numbers of
neutrons
• Some atoms have only one
stable isotope, others have
several
• Averaging the masses of the
isotopes in their correct
percentages gives the exact
atomic mass for each
element
• Unstable isotopes break
down (radioactive decay)
deuterium (H-2),
tritium (H-3),
least common,
radioactive
For example
12
• Different isotopes are
identified by their
mass numbers
C
13
C
14
C
6 protons + 6 neutrons
6 protons + 7 neutrons
6 protons + 8 neutrons
Sometimes written C-12, C-13, C-14
Mass number is the protons + neutrons
Calculating Atomic Mass Using
Isotopes
• Determine the mass of
each isotope based on its
abundance (percent of
each isotope found)
– Remember, convert
percents into decimals
– Multiply by the mass
number of the isotope
Cl-35
76%
35 x 0.76 = 26.6
Sample of
chlorine
* Your calculated
answer should be very
close to the mass on the
periodic table
Cl-37
24%
37 x 0.24 = 8.88
26.6 + 8.88 = 35.48 amu
Actual mass =
35.453 amu
• Slides 1 – 15 for honors
• Slides 17-20 for reg
Chapter 6
Atoms
Section 1 Atomic Theory
• Atomic Theory (by John
Dalton) published in 1803
– All substances are made
from atoms. Atoms cannot
be created, divided or
destroyed.
– Atoms of the same element
are exactly alike.
– Atoms can join together to
form new substances.
Parts of the Atom
Particle
Charge
Location
Size
Proton
Positive
In the nucleus
1 a.m.u.
Neutron
No charge
(neutral)
In the nucleus
Almost 1
a.m.u.
Negative
Outside the nucleus,
orbiting at nearly the
speed of light
Very tiny,
1/1000th
a.m.u.
Electron
Structure of the Atom
• Protons
+
– Positively charged
– Found in the nucleus of the
atom (center)
– Mass of 1 amu (atomic mass
unit)
– Gives the element its atomic
number on the periodic table
• #1 (hydrogen) has 1 proton
• #4 (beryllium) has 4 protons
Protrons were discovered by
Ernest Rutherford in 1911 and
he discovered the empty space
within an atom in 1909
• Neutrons
– Neutral charge ( no
charge)
– Found in the nucleus
(center)
– Mass slightly smaller
than a proton, still
considered 1 amu
– Protons + Neutrons @
atomic mass (rounded
to the nearest whole
number)
N
Electron
• Electrons
– Negatively charged
particles
– Found outside the nucleus,
moving at nearly the speed
of light, in specific levels
– Most commonly atoms are
neutral particles having
equal numbers of protons
and electrons
– Very small ( about 1/1000th
of a proton)
Electrons were discovered by
J.J. Thompson in 1897
Proton
Neutron
* In 1913 Niels Bohr suggested that electrons
travel in specific paths called Electron Shells
• Each level can only
contain a certain
number of electrons
before it is full
• Each level will fill
completely before
electrons go to the
next level
• Lower levels fill first