Transcript Physical Properties

Environmental Chemistry Unit 2
Materials:
Structure and Uses
http://www.ccsdualsnap.com/miscellan.htm
Coin Design Competition
• How are coins made?
• http://www.usmint.gov/mint_tours/index.cf
m?action=vtShell
Link to Previous Learning
• We have learned about physical properties of
matter:
– Physical properties: Property of an object that can be
observed or measured without changing the substance
• We have also learned the names and symbols of
common elements
• In this unit we will learn about chemical
properties, organization of the elements on the
periodic table and how it relates to properties of
the atom
Properties Make the Difference
Section 1
Coin-Design Competition
• In order to apply for the Coin-Design
Competition, we must decide the
composition of the coins material
• Need to research the properties of elements
that could be used to make the coin
Physical and Chemical
Properties of Elements
Physical Properties
• Property of an object that
can be observed or
measured ______________
________________________
• Examples:
– Density
– Color
– Melting Point
Chemical Properties
• _______________________
_______________________
• Must alter substance to
observe
• Indicates how a substance
_______with something else
• Examples:
– Flammability
Physical and Chemical
Changes
Physical Changes
• ____________________
of the substance
Chemical Changes
• ________________
________________
• Examples:
• Examples:
– Crush
– tear
– change in state (solidliquid-gas)
– food cooks
– iron rusts
– wood burns
Study Buddy Review
Classify each as a physical or chemical
property of matter:
•
•
•
•
•
•
•
•
•
•
Blue Color
Ability to Rust
Density
Flammability
Reacts with a base to form water
Boiling Point
Reacts with water to form a gas
Luster
Mass
Odor
The Periodic Table of Elements
(Section 4)
Chemical Elements
• Elements: Pure substances that __________
_____________________________________
– Composed of atoms
– Organized by the Periodic Table of Elements
Dobereiner’s Triads
THE LAW OF TRIADS:
The atomic mass of the middle element of the triad
is equal to the ________________________ of the
other two elements.
EXAMPLE:
Lithium
Sodium
Potassium
Atomic Mass of 7
Atomic Mass of 23
Atomic Mass of 39
According to Dobereiner’s Law, the atomic mass of sodium
Should equal the arithmetic mean of lithium and potassium.
(7+39)/2 = 23, which is the mass of sodium.
Problems with Dobereiner’s
Law of Triads.
1) _______________________________________
_______________________________________________________
2) The law did not work for very low or very high
massed elements such as F, Cl, and Br.
3) As techniques improved for measuring atomic
masses accurately, the law became obsolete.
Dobereiner’s research made chemists look at groups of
elements with similar chemical and physical properties.
Newland’s Law of Octaves
When placed in increasing order of their atomic
masses, every __________________________
and _________________________.
Li Be B C N
Na Mg Al Si P
K Ca
O
S
F
Cl
Problems with
Newland’s Law of Octaves
1) It was not valid for elements that had atomic
masses higher than Ca.
2) When more elements were discovered
(Noble gases) they could not be accommodated in his
table.
However, the modern periodic table does draw from the
concept of periods of eight.
Mendeleev and Meyer
• Published nearly identical schemes for classifying
elements
• Arranged elements by ______________________
• Mendeleev generally given more credit
– Published first
– More successful at demonstrating value of table
– Predicted discovery of new elements, properties
of new elements
Mendeleev’s Table: the first periodic table of the elements.
He arranged the table so that elements in the ____________
______________________________________.
Problems with Mendeleev’s Table:
1) The positions of isotopes could not be
accommodated within the table.
2) In order to make the elements fit the requirements,
Mendeleev was forced to put an element of slightly
higher atomic weight ahead of one of slightly lower
atomic weight.
Henry Moseley (1887-1915)
• Developed concept of ________________
– amount of positive charge in the nucleus
• Later determined that arranging periodic
table according to increasing atomic number
eliminated problems seen in Mendeleev’s
table
Why is it the “periodic” table?
• Periodic Law: when elements are
arranged in order of __________
_________________, their physical
and chemical properties show a
periodic pattern
Study Buddy Review
• Describe the contribution each person
below made to the development of the
periodic table:
–
–
–
–
–
Johan Dobereiner
John Newland
Dmitri Mendeleev
Julius Meyer
Henry Moseley
Parts of the Periodic Table
Parts of Periodic Table
• Groups/families: vertical columns
–
–
–
–
–
Alkali metals:
Alkali earth metals:
Boron, carbon, nitrogen, oxygen families
Halogens:
Noble gasses:
• Horizontal rows are called ___________
• There are 7 periods
1A
• The elements in the A groups are
called the representative elements
2A
3A 4A 5A 6A 7A
8A
0
Parts of Periodic Table
• Metals: __________ of staircase
• Nonmetals: __________ of staircase
• Metalloids: elements adjacent to staircase
(except Al, Po)
The group B are called the
transition metals
 These
are called the inner
transition metals and they
belong here
Study Buddy Review
• Identify the follow parts of the periodic table:
–
–
–
–
–
–
–
–
Halogens
family
Alkali metals
Metals
Inner transition metals
Noble gases
Metalloids
Period
The Atom
Early Models of the Atom
Atom
• Smallest particle of an
element that
____________________
____________________
____________________
Democritus & Kanada
• Kanada
Ancient Indian philosopher
4 elements
air
fire
earth
water
Made up of tiny particles
• Democritis
Greek Philosopher
~450 BC
Logic
___________________________
Contributing Principles to Idea of
Atom
• __________________
__________________
• Antoine and Marie
Lavoisier
• Conducted controlled
experiments and made
many quantitative
measurements
• Late 1700’s
http://images.search.yahoo.com/search/images/
Contributing Principles to Idea of
Atom
http://images.search.yahoo.com/search/images/
• Law of Definite
Composition
• A given compound
always
__________________
__________________
__________________
by mass
• Joseph Louis Proust
• 1799
John Dalton’s Atomic Theory (1803)
www.english.upenn.edu/~jlynch/Frank/People/dalton.html 2k
1. Elements composed of small
particles called _________
2. All atoms of a given element are
the same, but different from
other elements
3. Atoms ______________
__________________in a chemical
reaction
1. Compounds are composed of
atoms combined in simple
whole number ratios
Study Buddy Review
• Describe the
contribution of each
towards the historical
development of the
atom:
–
–
–
–
Lavoisier
Proust
Democritus
Dalton
What is inside the atom?
J.J. Thomson (1897)
• Cathode Ray Tube Experiments
Conclusions:
• Stream of negative particles
that have mass
• Named________________
• Atoms are not indivisible
• Found ratio:
(electrical charge of electron)
(mass of electron)
1.76 x 108 coulombs = 1 gram
of electrons
Robert Millikan (1909)
• Oil Drop
Experiment
Measured
_______________
_______________
• Charge of one
electron =
-1.6x10-19C
http://webphysics.davidson.edu/Alumni/ToHaynie/OilDrop/oilappa.htm
THUS….
Mass of e- =
Rutherford’s experiment
• English physicist Ernest Rutherford (1911)
• _________________________which can be
made a few atoms thick.
– alpha particles: positively charged helium nuclei
– A form of radioactivity
• When an alpha particle hits a fluorescent
screen, it glows.
How Rutherford explained results
• Atom is ____________
____________________
• Small dense, positive
piece at center.
(NUCLEUS)
• Alpha particles
are deflected by it if
they get close enough.
Credit for Subatomic Particles
• 1897 Thomson discovered the electron
– Used cathode ray tube
• (1918) Rutherford named positive charged particle
the proton
– Goldstein (1886) first discovered positively charged particle using
Cathode-ray tube with perforated cathode
– (1932) James Chadwick
– Discovered neutrons
Produced neutrons and their masses
Worked with cloud chambers
Subatomic Particles in Atom
Charge
Real mass
Relative
mass
p+
1.67 x 10 -24 g 1 amu
e-
9.11 x 10 -28 g 1/1840 amu
no
1.67 x 10 -24 g 1 amu
Study Buddy Review
• Name three subatomic
particles.
• Who is credited with
discovering each
particle?
• Describe the
Rutherford Gold Foil
Experiment.
Information from Periodic Table
Atomic Number and
Atomic Mass
• Chemical Symbol: abbreviation for element
name
• Atomic Number: ____________in nucleus
of atom (and electrons if neutral)
• Mass Number: __________________in
nucleus (whole number)
Isotopes
• Isotopes: atoms with the same # of protons
_____________________________
• Shorthand notation:
O168
O178
• Average Atomic Mass: weighted avg. mass
of atoms found in nature
Models of the Atom
Dalton Model of Atom
• Small, indivisible spheres
http://images.search.yahoo.com/search/images/
J.J. Thompson’s Model of Atom
• Plum Pudding Model,
1896
• Thought an atom was
like plum pudding
http://images.search.yahoo.com/search/images/
– Dough was positively
charged
– Raisins scattered
throughout the dough
were negatively charged
– Didn’t know about
neutrons at this time
Rutherford’s Model of the Atom
• Rutherford Model, 1911
• Thought atom was mostly
empty space
– Nucleus in center is dense,
positively charge
– Electrons (negatively
charged) are in empty
space surrounding nucleus
http://images.search.yahoo.com/search/images/
Bohr’s Model of the Atom
• Neils Bohr, 1913
• Similar to Rutherford’s
model
• Thought atom was
mostly empty space
– Nucleus in center is dense,
positively charge
– Electrons move in orbits
around the nucleus
http://images.search.yahoo.com/search/images/
(Modern) Quantum Mechanical Model
of the Atom
• Heisenberg,
Schrodinger, many
others, ~1926
• Think atom is mostly
empty space
– Nucleus in center is
dense, positively charge
– Electrons are around the
nucleus
– Cannot locate location of
electron at specific time
http://particleadventure.org/particleadventure/frameless/modern_atom.html