Transcript Classifying Matter and the Periodic Table

Classifying Matter and the
Periodic Table
From Chapter 8 & 10
in Trefil & Hazen The Sciences
Classification of Matter
…discuss the origin and development
of the idea of “atoms”.
• 530 B.C. Democritus
• atomos
• Smallest piece of
“uncuttable” matter
• atoms are eternal and
unchanging
• relationship between
atoms is constantly
shifting
Figure 8-1
Repeatedly dividing a bar of gold, just like cutting paper repeatedly,
produces smaller and smaller groups of atoms, until you come to a
single gold atom. Dividing that atom into two parts produces
fragments that no longer have the properties of gold.
Antoine Lavoisier’s
law of conservation of matter
• measured the mass
of substances
before and after
chemical reactions
• found that the
masses were
always equal
Joseph Proust’
law of constant composition:
• he found that a
given compound
always contains the
same elements in
the same
proportions by
mass
Dalton’s atomic theory of matter
• each element is composed of extremely
small particles called atoms
• all atoms of a given element are identical,
but they differ from those of other any
other element
Dalton’s atomic theory of matter
• a given compound
always has the same
relative numbers and
kinds of atoms
• atoms are neither
created nor destroyed
in any chemical
reaction
…distinguish between atoms and
elements.
• Atom = the smallest particle of an
element that retains the chemical
identity of that element.
• An element is a material made from a
single type of atom.
…evaluate evidence for the
existence of atoms.
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Behavior of a gas
Chemical combinations
Radioactivity
Brownian motion
X-ray crystallography
Atomic-scale microscopy
Mendeleev and the
Periodic Table of the Elements
Mendeleev’s Table
…interpret J.J. Thompson’s cathode
ray tube experiment.
Thompson’s Tube gave first
evidence of the electron
• “cathode” is the
connection to
negative source of
electricity
• The “ray” was a
stream of particles
carrying negative
electric charge
Interpret E. Rutherford’s gold foil experiment.
Figure 8-3
In Rutherford’s experiment, a beam of radioactive particles
was scattered by atomic nuclei in a piece of gold foil. A lead
shield protected researchers from the radiation.
• Discovery of the
electron
• Discovery of the
proton
• Discovery of the
neutron
3
Li
6.941
“Flame Test”
Bohr Model of the Atom
Figure 8-6
Stairs provide an analogy to energy changes associated
with electrons in the Bohr atom.
Figure 8-7
Electrons may jump between the energy levels shown in (a) and, in
the process, (b) absorb or (c) emit energy in the form of a photon.
Physical Properties…
• describe the physical
characteristics of a
substance, such as
color, hardness,
density, texture, and
phase.
Physical change…
• is a change in some
property of a
substance.
• Usually occur during
heating/cooling or
when there is a
change in pressure.
Chemical properties…
• characterize the tendency of a substance to
transform into a different substance.
Chemical change
• Atoms rearrange
during a chemical
change, switching
partners as previous
connections are
broken and new ones
are formed.
• Evidence?
• Physical change
• New attributes result
from new set of
conditions imposed
on the material
• Chemical change
• New attributes are the
physical properties of
a fundamentally
different material
Element: a pure substance containing
only one kind of atom
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Periodic Table – front cover and p 172
Element
symbol
Latin name
Sodium
Na
natrium
Potassium
K
kalium
Copper
Cu
cuprum
Gold
Au
aurum
Lead
Pb
plumbum
Atoms that compose an element may
combine in a variety of ways.
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Gold, Au
Sulfur, S8
Nitrogen, N2
Oxygen, O2
Compounds –atoms of different
elements combined in a fixed ratio
• Compounds have physical and chemical
properties different from the properties of
their elemental components
• NaCl, sodium chloride or table salt
• Fe2O3, iron oxide or rust
Mixtures = various combinations of
elements, compounds, or both
• Stainless steel is a mixture of the elements
iron, chromium, nickel and carbon.
• Our atmosphere is a mixture of nitrogen,
oxygen, argon, carbon dioxide, water
vapor, and pollutants.
How might we separate the following:
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Iron filings and sand
Sawdust and rubber washers
Salt and water
Oil and water
Point: Components of any mixture can be
separated by physical means.
Classification of Matter
Matter
Pure
Element
Impure
Compound
Heterogenous Mixture
Homogenous Mixture
Solution
Suspension
Pure Substance
• Element
– Gold, Au
– Hydrogen, H2
– Silicon, Si
• Compound
– Salt, NaCl
– Carbon Dioxide,
CO2
– Ammonia, NH3
Impure Substances
• Heterogenous
Mixture
– Sand in water
– Oil and water
– Salt and pepper
• Homogenous
Mixture
– Solution
– Suspension
Homogenous Mixture
• Solution
– Air (N2, O2)
– Salt water (NaCl,
H2O)
– Stainless Steel (Fe,
Cr, Ni, C)
• Suspension
– Milk (water, solid
proteins)
– Blood (water, solid
cells, nutrients)
– Fog (air, tiny water
droplets)
Periodic Table Basics: Element Symbol, Atomic
Number, Average Atomic Mass, Families and Periods.
Figure 8-13
The periodic table of the elements. The weights of the elements
increase from left to right. Each vertical column groups elements
with similar chemical properties.
• Average Atomic Mass = sum of protons
and neutrons; an average of the relative
abundance of the isotopes for that element
92
U
238.028
…distinguish between properties of
metals, metalloids, and nonmetals.
…compare and contrast families of elements in
terms of their chemical properties.
Alkali Metals, group IA (1)
…compare and contrast families of elements in
terms of their chemical properties.
Alkaline Earth Metals, group IIA (2)
…compare and contrast families of elements in
terms of their chemical properties.
Halogens, group VIIA (17)
…compare and contrast families of elements in
terms of their chemical properties.
Noble Gases, group VIIIA (18)
NaCl CaCl2 MgO Al2O3
H2O CO2 CH4 NH3
Text questions:
• Chapter 8
– Discussion Questions 6-10 p. 175
• Chapter 10
– Discussion Questions p. 216: 1,2,4,5,6,7,11
and Problems 1, 2, 3.