Transcript Chapter 3-part 1

Chapter 3 Atoms and
Elements
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3.1 Elements and Symbols
Elements are
• pure substances that cannot be separated into simpler
•
substances by ordinary laboratory processes.
the building blocks of matter.
gold
carbon
aluminum
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Sources of Some Element Names
Some elements are
named for planets,
mythological figures,
minerals, colors,
scientists, and
places.
TABLE 3.1
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Symbols of Elements
A symbol
• represents the name of an element.
• consists of 1 or 2 letters.
• starts with a capital letter.
1-Letter Symbols
C
carbon
N nitrogen
F
fluorine
O oxygen
2-Letter Symbols
Co
cobalt
Ca
calcium
Al
aluminum
Mg
magnesium
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Symbols from Latin Names
Several symbols are derived from Latin names as shown
below.
Cu, copper (cuprum)
Fe, iron (ferrum)
Au, gold (aurum)
Ag, silver (argentum)
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Physical Properties of Elements
The physical properties of an element
• are observed or measured without changing its identity.
• include the following:
Shape
Density
Color
Melting point
Odor and taste Boiling point
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Physical Properties of Elements
Some physical properties of
copper are:
Color
Luster
Melting point
Boiling point
Conduction
of electricity
Conduction
of heat
Red-orange
Very shiny
1083 °C
2567 °C
Excellent
Excellent
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Example
Select the correct symbol for each.
A. Phosphorous
1) K
2) P
3) Ph
B. Aluminum
1) Al
2) Au
3) An
C. Iron
1) Ir
2) FE
3) Fe
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Examples
Select the correct name for each symbol.
A. Ne
1) neon
2) nitrogen
3) nickel
B. K
1) potassium
2) phlogiston 3) phosphorus
C. Au
1) silver
2) agean
3) gold
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3.3The Periodic Table
Development of the Periodic Table
Mendeleev’s Periodic Table (1871)
Until the discovery of the proton, the elements were typically
organized by increasing atomic weight.
The modern organization is by increasing atomic number.
Groups and Periods
On the periodic table,
• elements are arranged according to similar properties.
• groups contain elements with similar properties in vertical
columns.
• periods are horizontal rows of elements.
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Groups and Periods
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Names of Some Representative
Elements
Group Numbers
Group Numbers
• use the letter A for the representative elements (1A to 8A) and
the letter B for the transition elements.
• also use numbers 1-18 to the columns from left to right.
Elements and the Periodic Table
Alkali Metals
Group 1A (1), the alkali metals, includes lithium,
sodium, and potassium.
Halogens
Group 7A (17), the
halogens, includes
chlorine, bromine,
and iodine.
Examples
Identify the element described by the following:
A. Group 7A (17), Period 4
1) Br
2) Cl
3) Mn
B. Group 2A (2), Period 3
1) beryllium
2) boron
3) magnesium
C. Group 5A (15), Period 2
1) phosphorus
2) arsenic
3) nitrogen
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Metals, Nonmetals, and Metalloids
The heavy zigzag line separates metals and
nonmetals.
• Metals are located to the left.
• Nonmetals are located to the right.
• Metalloids are located along the heavy zigzag line
between the metals and nonmetals.
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Metals, Nonmetals, and Metalloids on the
Periodic Table
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Properties of Metals, Nonmetals, and
Metalloids
Metals
• are shiny and ductile.
• are good conductors of heat and electricity.
Nonmetals
• are dull, brittle, and poor conductors.
• are good insulators.
Metalloids
• are better conductors than nonmetals, but not as good as metals.
• are used as semiconductors and insulators.
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Comparing a Metal, Metalloid, and
Nonmetal
TABLE 3.4
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SUMMARY
 Periods: 7 horizontal rows.
 Groups: 18 vertical columns.
 International standard: 1-18
 US system: 1A-8A, 1B-8B
Examples
Identify each of the following elements as
1) metal, 2) nonmetal, or 3) metalloid.
A. sodium
B. iodine
C. Argon
D. iron
E. Silicon
____
____
____
____
____
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Examples
Match the elements to the description.
A. Metals in Group 4A (14)
1) Sn, Pb
2) C, Si
3) C, Si, Ge, Sn
B. Nonmetals in Group 5A (15)
1) As, Sb, Bi
2) N, P 3) N, P, As, Sb
C. Metalloids in Group 4A (14)
1) C, Si, Ge,
2) Si, Ge
3) Si, Ge, Sn, Pb
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3.4 The Atom
The Law of Multiple Proportions and Dalton’s Atomic Theory
•
Elements are made up of tiny particles called atoms.
•
Each element is characterized by the mass of its atoms. Atoms
of the same element have the same mass, but atoms of
different elements have different masses.
•
The chemical combination of elements to make different
chemical compounds occurs when atoms join in small wholenumber ratios.
•
Chemical reactions only rearrange how atoms are combined in
chemical compounds; the atoms themselves don’t change.
Atomic Structure: Electrons
Cathode-Ray Tubes: J. J. Thomson (1856-1940) proposed that cathode rays
must consist of tiny negatively charged particles. We now call them
electrons.
Rutherford’s Gold Foil Experiment
Copyright © 2009 by Pearson Education, Inc.
Rutherford’s Gold Foil Experiment
In Rutherford’s gold foil experiment, positively
charged particles
•
were aimed at atoms of gold.
•
mostly went straight through the atoms.
•
were deflected only occasionally.
Conclusion:
There must be a small, dense, positively charged
nucleus in the atom that deflects positive particles that
come close.
Subatomic Particles
Atoms contain subatomic particles.
•
•
•
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Protons have a positive (+) charge.
Electrons have a negative (-) charge.
Neutrons are neutral.
Like charges repel and unlike charges attract.
Structure of the Atom
An atom consists
• of a nucleus that
contains protons
and neutrons.
• of electrons in a
large, empty space
around the nucleus.
Atomic Mass Scale
On the atomic mass scale,
• 1 atomic mass unit (amu) has a mass equal to 1/12 of the
mass of the carbon-12 atom.
• a proton has a mass of about 1 (1.007) amu.
• a neutron has a mass of about 1 (1.008) amu.
• an electron has a very small mass, 0.000 549 amu.
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Particles in the Atom
TABLE 3.5
Examples
Identify each statement as describing a
1) proton, 2) neutron, or 3) electron.
A. found outside the nucleus
B. has a positive charge
C. is neutral
D. found in the nucleus
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Examples

Is each of the following statements true or false?
◦ Protons are heavier than electrons
◦ Protons are attracted to neutrons
◦ Electrons are small that they have no electrical charge
◦ The nucleus contains all the protons and neutrons of an
atom
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