Atomic Models
Democritus
• 430BC gave the atom it’s name.
• Atom: uncuttable
• Dark Ages no further work has been recorded
• The idea of atoms began to develop again in
the 1600’s as people did experiments.
John Dalton’s Atomic Theory 1776
• Atoms
1) Consist of elements that cannot be divided
2) All atoms of same element are exactly alike
and have the same mass.
3) An atom of one element cannot be changed
into an atom of another element.
4) Compounds are formed when atoms of more
than one element are combined.
J.J. Thomsen’s model (1897)
• Plum pudding or watermelon model
• Discovered atoms contain charged particles,
positive and negative.
• Positive charge must balance negative charge.
Ernest Rutherford
1911
• Discovered that atoms are mainly empty
space with a positively charged nucleus.
• His new model is like a cherry. The dense
nucleus surrounded by empty space.
• Protons are in the nucleus.
Niels Bohr’s Model 1913
• Electrons are found in specific energy levels or
orbitals.
• Each possible orbit has a fixed energy.
Electrons furthest from the nucleus have the
highest energy.
Modern Model 1932
• Electrons move rapidly within a “cloud”
around the nucleus.
• Nucleus contains protons and neutrons.
• Clouds contain electrons
Atomic model videos
• History of atom short version
http://www.youtube.com/watch?v=QbWKF9uDF7w
•
Thomsen’s
experiment
http://www.youtube.com/watch?v=CsjLYLW_3G0
• History of atom long version
http://www.youtube.com/watch?v=njGz69B_pUg
• Rutherford’s experiment
http://www.youtube.com/watch?v=XBqHkraf8iE
Periodic Table
• Organizes the elements by atomic number,
mass and families.
• Mendeleev built the periodic table in the
1800’s.
http://www.periodictable.com/
Counting Particles
• Atomic Number
Tells you the number of protons
and electrons in an element
Atomic Mass
• Atomic mass tells you the weight of each
nucleus.
• Nucleus mass = protons + neutrons
• Each mass is written in atomic mass units
(a.m.u.)
How to find # of neutrons
• To find # of neutrons, subtract the atomic
mass from the atomic # and round.
• For example
• Oxygen = 15.98 (16) – atomic # (8) = 8
neutrons
Models of atoms
• Model the atoms nucleus and place electrons
in an orbit
Neutrons
• The bigger the element the more neutrons
you will have.
• The neutrons hold the nucleus together.
• How many neutrons would gold have?
Isotopes
• Isotopes of an element have same number of
protons, different number of neutrons.
• That is why atomic mass has decimal parts.
The mass is a weighted average like grades.
Isotopes
• Abundance is how common it is to find in
nature. You multiply the weight by the
abundance to get the weighted average.
Nuclear fusion on sun
Patterns of the periodic table
• Rows = periods
• Each period goes from metals to metalloids to
nonmetals.
Real periodic table
Cylinder periodic table
Groups of the periodic table
• Groups are known as families
• Elements in each family have similar chemical
properties.
• The elements in a family all have the same
valence (outermost) # of electrons.
Alkali metals
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•
•
•
Most reactive metals in the periodic table.
Never found uncombined in nature
Have 1 valence electron
Sodium (salt)
reactivity of alkali metals
Alkaline Earth
• Group 2 elements
• Less reactive than alkali metals, but still
reactive.
• Calcium – found in bones, teeth
• Have 2 valence electrons
alkaline earth metals
Transition Metals
• Groups 3-12
• Iron, copper, gold, nickel, silver
• Hard and shiny solids, except mercury at room
temperature.
• Good conductors of heat and electricity.
• Less reactive than Group 1 or 2
Properties of metals
• All metals transfer electrons to become stable
when they are reacted with a nonmetal.
Metalloids
• Some properties of metals and some of
nonmetals.
• Solids at room temperature
• Conductivity most important property.
• Silicon and germanium are used to make chips
for computers/cellphones etc.
Nonmetals
•
•
•
•
•
•
Groups 13-18
Lacks most of the properties of metals.
Poor conductors of heat and electricity
Brittle as solids
Many are gases at room temperature
Carbon, Sulfur, and iodine are solids at room
temperature
Properties
• Gain or share(covalently) electrons to become
stable.
• When metals bond with nonmetals the metal
transfers it’s electrons to the nonmetal.
i.e. salt
• When nonmetals bond with nonmetals the
elements share electrons.
i.e. water
Jigsaw Element Project
• You are to choose one of the elements in your
family.
• You will need to make a visual aid (2D or 3D)
of your element and use to present to the
class.
• All information required must be included in
your poster/ and or presentation.
• You will present as a group, each person must
have a part.
Requirements
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•
•
•
•
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Atomic Symbol (atomic number, atomic mass)
# of protons, electrons, and neutrons
Correct model of atom
Physical properties of the element
# of valent electrons in family
Common uses of the element and/or compounds
made from the element.
• Similarities and differences to other elements in
the family.
Rubric
Visual aid
• Contains required information
20 pts.
• Follows ABCD
10 pts.
(accurate, big, colorful, detailed)
Group work
10 pts.
• All group members were on task and used
class time wisely.
• Group met the timeline
10 pts.
Rubric Continued
Presentation
• All group members presented
• Voices/Eye Contact (average)
• Attentive to other presentations
10 pts.
10 pts.
10 pts.
Timeline
• You will have two days and the weekend to get
your project done and presented.
Carbon Family
Nitrogen family
Oxygen Family
Halogen family
Noble Gases
Metalloids