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Date: 10-14-14
Day Plan: 1) Review Atomic Time Line
2) Notes on Atoms
3) Time to work on Homework
Opener:
1) Which two sub-atomic particles have a charge?
2) Which two partials have essential the same mass?
3) Which Sub-atomic practical has a really small mass?
Atoms,
Molecules,
and Ions
Subatomic Particles
• Protons and electrons are the only particles that have
a charge.
• Protons and neutrons have essentially the same
mass.
• The mass of an electron is so small we ignore it.
Atoms,
Molecules,
and Ions
• Monday – Notes
• Tuesday – Candium Activity (Calculating
Isotopes)
• Wednesday – Answers to Candium Activity
- Homework Due
• Thursday – Video (For Sure Happening!)
Atoms,
Molecules,
and Ions
The Electron
• Streams of negatively
•
charged particles were
found to emanate from
cathode tubes.
•
• J. J. Thompson is credited
with their discovery (1897).
The Atom, circa 1900:
“Plum pudding” model,
put forward by
Thompson.
Positive sphere of matter
with negative electrons
imbedded in it.
Atoms,
Molecules,
and Ions
The Nuclear Atom
Discovery of the Nucleus
Ernest Rutherford shot
 particles at a thin
sheet of gold foil and
observed the pattern of
scatter of the particles.
Since some particles
were deflected at
large angles,
Thompson’s model
could not be correct.
Atoms,
Molecules,
and Ions
The Nuclear Atom
• Rutherford postulated a very small, dense
nucleus with the electrons around the outside of
the atom.
• Most of the volume of the atom is empty space.
• Protons were discovered by Rutherford in 1919.
• Neutrons were discovered by James Chadwick Atoms,
Molecules,
in 1932.
and Ions
• Notes Over View
A) Daltons Theory Of Atomic Mass
B) Law of Chemistry
C) Symbols of an Element
D) Average Mass of an Isotope
Atoms,
Molecules,
and Ions
Notes : Atoms, Molecules, and Isotopes
A) Daltons Atomic Theory of Matter
• Idea proposed by
John Dalton in the 19th
century (1803)
• Proposed the modern
atomic theory
Atoms,
Molecules,
and Ions
Dalton’s Theory
1. Element are made up of extremely small
particles called atoms.
2. All atoms of the same element have the same
size, mass, and chemical properties.
3. Atoms cannot be created, divided into smaller
particles or destroyed.
4. Different atoms combine in simple whole
number ratios to form compounds. 2:1
5. In chemical reactions, atoms are separated,
Atoms,
combined or rearranged.
Molecules,
and Ions
B) Laws of Chemistry
Law of Definite Proportions
1) Elements combining to form a compound =
always combine in definite proportions
Example: sucrose (sugar) will always be 42.2%
carbon, 6.50% hydrogen, and 51.30% oxygen
2) Percent by mass = mass of element x 100
mass of compound
Atoms,
Molecules,
and Ions
Example:
• What is the percent by mass of carbon in
sugar can if you have 211.0 g carbon in
500.0 g of sugar?
Percent by mass = mass of element x 100
mass of compound
Percent by Mass = 211.0 g X 100 =
500.0 g
Atoms,
Molecules,
and Ions
Example
• What is the percent by mass of hydrogen in
sugar cane if you have 32.5 g of hydrogen in
500 g of sugar cane?
Percent by mass = mass of element x 100
mass of compound
Percent by mass = 32.5 g x 100 =
500.0 g
Atoms,
Molecules,
and Ions
Law of Multiple Proportions
Compounds can be composed of the same
elements (with different masses) in whole
number ratios. H2O
• Example:
The mass ratio of copper to chlorine in compound
I is two times the mass ratio of copper to chlorine
in compound II.
Law of Conservation of Mass
Mass at the beginning of a chemical
Atoms,
reaction = mass at the end of the reactionMolecules,
and Ions
C) Symbols of Elements
Elements are symbolized by one or two letters.
Atoms,
Molecules,
and Ions
Atomic Number
•
All atoms of the same element have the
same number of protons:
•
The atomic number (Z)
Atoms,
Molecules,
and Ions
Atomic Mass
• The mass of an atom in atomic mass units (amu)
• Mass = total number of protons and neutrons in the
atom.
Atoms,
Molecules,
and Ions
Isotopes:
• Atoms of the same element with different masses.
• Isotopes have different numbers of neutrons.
11
C
6
12
C
6
13
C
6
14
C
6
Atoms,
Molecules,
and Ions
Atomic Mass
Atomic and
molecular masses
can be measured
with great accuracy
with a mass
spectrometer.
Atoms,
Molecules,
and Ions
D) Average Mass (of an Isotope)
• Because in the real world we use large
amounts of atoms and molecules, we use
average masses in calculations.
• Average mass is calculated from the isotopes of
an element weighted by their relative
abundances. (%)
Atoms,
Molecules,
and Ions
Example
• Element X has two natural isotopes. The
isotope with a mass of 10.012 amu (10X) has a
relative abundance of 19.91%. The isotope
with a mass of 11.009 amu (11X) has a relative
abundance of 80.09%. Calculate the atomic
mass of this element.
10X
% 10X
10.012 .1991
(19.91/100)
+
11X
% 11X
+ 11.009 .8009
(80.09/100)
=
=
Atoms,
Molecules,
and Ions
Practice
• Calculate the atomic mass of bromine. The two
isotopes of bromine have atomic masses and
relative abundance of 78.92 amu (50.69%) and
80.92 amu (49.31%.
Atoms,
Molecules,
and Ions