Download Atomic Masses

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Atom
Proton
Nucleus
Neutron
Electron
Mass number
Atomic number
Atomic mass unit
Isotope
Atomic Mass
• First column: words
• Second column:
definition from text
• Third column:
definition in your own
words
• Fourth column: Picture
or example
Due Tomorrow!
SC3. Students will use the
modern atomic theory to
explain characteristics of
atoms.
“Atomic Theory
and Structure”
 OBJECTIVES:
 Explain
Dalton’s atomic theory.
 Identify the parts of an atom,
their location, charge, and
relative mass.
 Determine the numbers of
subatomic particles in an atom.
Democritus’s Atomic Philosophy
 Democritus-
all matter
is made up of
imperishable, indivisible
units, which
he called atoma.
Dalton’s Atomic Theory
1)All elements are
composed of atoms.
John Dalton
(1766 – 1844)
2) Atoms of the same
element are identical.
Atoms of different
elements are different.
3) Atoms of different elements can
combine to form compounds.
4) In chemical reactions, atoms are
combined, separated, or
rearranged, but never changed into
atoms of another element.
Modern Theory
 One
change to Dalton’s atomic
theory is that atoms are divisible
into subatomic particles:
 Electrons
 Protons
 Neutrons
The Subatomic Particles
Location
Charge
Relative
mass in amu
Proton
Neutrons
Electrons
0.00055 amu
amu: mass of 1/12
of a carbon atom
Function
Atom Math
Atomic number:
number of protons
(and electrons IF atom
is neutral)
Atomic mass:
called
mass number when
rounded to nearest whole
number. Mass Number
equals protons + neutrons.
Atom Math



Protons: atomic number
Electrons: same as protons if atom is neutral
Neutrons: mass number – atomic number
protons: ________
neutrons: ________
electrons: ________
Element
carbon
Phosphorus
Gold
Atomic
Number
Number of
Protons
Number of
Electrons
Number of
Neutrons
Symbol Shorthand
Carbon
Superscript →
Subscript →
Mass
number
Atomic
number
X
Phosphorus
Gold
Work Session

Subatomic Particle Counting WS—15 minutes
Atomic Structure
Part 2“Isotopes and Ions”
Ions

When an atom loses or gains electrons it
is called an ion. The number of electrons
lost or gained is indicated by a charge.
Element
Protons
Oxygen
Gains 2 electrons
Aluminum
Loses 3 electrons
Beryllium
Loses 2 electrons
Bromine
Gains 1 electron
Electrons
Ion
Assignment
Ion Practice Set
Finish for homework
Ion Review
Element
Sulfur
Sodium
Boron
Number of
protons
Number of
Electrons
Gains 2
electrons
Loses 1
electron
loses 3
electrons
Ion
Atomic Structure
Part 2“Isotopes and Ions”
Isotopes
Atoms of the same element can
have different numbers of
neutrons.
Thus, different mass numbers.
Naming Isotopes

To distinguish between isotopes of the same
element, put the mass number after the name of
the element:
A
Z
Oxygen-18
Aluminum-25
10Be (beryllium-10)
79
Br (bromine-79)
Potassium-41
X
Protons
Neutrons
Isotopes
Elements occur in
nature as mixtures
of isotopes.
So, atoms of the
same element aren’t
necessarily the
same….
Isotope Review
Protons
Carbon-12
Carbon-14
Uranium-238
Uranium-235
Hydrogen-1
Hydrogen-2
Hydrogen-3
Neutrons
Work Session

Complete Ion Practice Set and Isotope Practice
Sets (15 minutes)
Atomic Mass

The average atomic mass: is based on
the abundance (percentage) of each
variety of that element in nature.
Lesson Preview
Argon has three naturally occurring isotopes:
argon-36, argon-38, and argon-40. Based on
argon’s reported atomic mass, which isotope do
you think is the most abundant in nature?
Poll everywhere response
To calculate the average
atomic mass:
Multiply the atomic mass of
each isotope by it’s
abundance percentage
(expressed as a decimal),
then add the results.
Atomic Masses
Atomic mass is the average of all the
naturally occurring isotopes of that element.
Isotope
Carbon-12
Atomic % in
mass
nature
98.89%
Carbon-13
1.11%
Carbon-14
<0.01%
negligible
Carbon = 12.011
Average Atomic Mass
Rubidium has two common isotopes, Rb-85 and
Rb-87. If the abundance of Rb-85 is 72.2% and
the abundance of Rb-87 is 27.8%, what is the
average atomic mass of rubidium?
On Your Own
Titanium has five common isotopes: 46Ti (8.0%),
47Ti (7.8%), 48Ti (73.4%), 49Ti (5.5%), 50Ti (5.3%).
What is the average atomic mass of titanium?
Beanium Lab
Purpose: To illustrate the
relationship between isotopic
mass, isotopic abundance,
and atomic mass.
Lab Hints
 Read
the instructions!
 Everyone participate in counting
beans.
 Do not lose your beans and clean up
when you are finished.
 Work
on the following assignments:
◦ Beanium Lab
◦ Average Atomic Mass Practice
Worksheet