Download Lecture 4

Chemistry 103
Lecture 4
Outline
I. Matter Classified (CH3)
II. The Periodic Table (CH4)
- The “Atom” defined
- History
- Atomic Symbols
- Atomic Mass
Density in Review
• What mass of gold (density = 19.3g/cm3)
occupies the same volume as 80.0g of
lithium (density = 0.534g/cm3)?
Chemical vs Physical???
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Popping a balloon
Burning a marshmellow
Snapping a twig
Water evaporating from a lake
Metabolizing a meal
Frying an egg
Matter
Pure Substance
Element Compound
Mixture
Pure Substances: Compounds
• Compounds
– A chemical combination of 2 or more elements.
– A pure substance that can be broken down into simpler
substances by chemical means.
Salt (NaCl)
Table sugar (C12H22O11)
Water (H2O)
NOTE: CO is different from Co
Elements in a Compound
“Table salt” is
a compound
that contains
the elements
sodium and
chlorine.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Pure Substances
Elements and Compounds
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Elements and compounds have definite compositions, and each has a set of
properties that are unique.
Which formulas represent elements (A) and which represent compounds
(B)?
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C
CO2
NH3
C60
(A)
(B)
(B)
(A)
Matter
Pure Substance
Element Compound
Mixture
MATTER
• Mixtures: a physical combination of two or
more pure substances in which each
substance retains its own chemical identity
Mixtures
A mixture is a type of matter that consists of:
• Two or more substances that are physically mixed, not
chemically combined
• Two or more substances in different proportions
• Substances that can be separated by physical methods
Example: Pasta and water can be separated with a strainer.
Matter
Pure Substance
Element
Compound
Mixture
Heterogeneous Homogeneous
Mixtures
• Homogeneous Mixtures (solutions)
– The composition is uniform throughout
– The different parts of the mixture are not visible
– air, salt water, alloys (i.e. brass, bronze)
• Heterogeneous Mixtures
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–
–
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The composition of substances is not uniform
The composition varies from one part of the mixture to another
The different parts of the mixture are visible
potting soil, oil and water
Classification of Matter
Elements v. Compounds v.
Mixtures
• Identify each of the following as an element(A),
compound(B), homogeneous mixture(C), or
heterogeneous mixture(D).
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carbon monoxide (CO)
oxygen (O2)
salt mixed with sugar
salt mixed with water
oil and water
A closer look at Elements &
The Periodic Table
Modern
Periodic Table
• Mendeleev – Father of the Periodic Table
• Periodic Law of the Elements – when elements are arranged in a
particular order (increasing atomic number), elements of similar
properties occur at periodic intervals
• Arranged into:
– Groups/families – vertical columns
– Periods – horizontal rows
http://www.woodrow.org/teachers/chemistry/institutes/1992/MENDELEEV.GIF
Arrangement of the Periodic Table
The blocks of the periodic table:
The Periodic Table – All Stretched
Out
Names of Some Representative
Elements
• Several groups of representative elements are
known by common names.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Organization of the Periodic Table
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Metals
– Have luster, are malleable, conduct electricity
Nonmetals
– Do not have the properties of metals
Metalloids
– Have some metallic properties and some nonmetallic properties
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A closer look still
The Conjecture of Atoms
• As early as 500 B.C., Greek Philosophers
proposed that all matter is made up of atoms
– Atom:
• The smallest individual particle of an element that
maintains the properties of that element
• Atomos - indivisible
http://members.aol.com/dcaronejr/ezmed/atom.jpg
http://www.aperfectworld.org/clipart/science_technology/atom.gif
Dalton’s Law of Atomic Theory
1. All matter is composed of
extremely small particles called
atoms.
2. Atoms of a given element are
identical in their physical and
chemical properties.
3. Atoms of different elements
differ in their physical and
chemical properties.
http://www.kjemi.uio.no/software/dalton/graphics/john_dalton.gif
Dalton’s Law of Atomic Theory
4.
Atoms of different elements
combine in simple, wholenumber ratios to form
compounds.
5. In chemical reactions, atoms are
combined, separated, or
rearranged but never created,
destroyed, or changed.
http://www.kjemi.uio.no/software/dalton/graphics/john_dalton.gif
Atom Defined
• An atom is the smallest particle of an
element that can exist and still have the
properties of the element. The fundamental
building block of matter.
Subatomic Particles
Today, we know that atoms are made up of
smaller, more fundamental particles called
subatomic particles.
Protons, Electrons & Neutrons
Electron Discovered
• 1898 - J.J. Thomson Proposed the “Raisin
Muffin” model of the atom.
e-
e-
e-
Rutherford’s Gold-Foil
Experiment
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Structure of the Atom
• An atom is composed of a nucleus and an area
called the electron cloud
– The nucleus is very small compared to the size of the
atom
– The nucleus contains the protons and the neutrons
– The electrons are constantly moving around in the
electron cloud
– In a neutral atom, the number of electrons is equal to
the number of protons
Atoms:
Composed of 3 Subatomic Particles
Symbol
Relative
Charge
Mass
Proton
p or p+
+1
1.673x10-24g
Neutron
n or no
0
1.675x10-24g
Electron
e-
-1
9.110x10-28g
The Atom
• The nucleus of an atom carried most of the
mass. A matchbox full of material of such
density would weigh 2.5 billion tons
The Atom
If an atom were scaled upwards in size so
that the nuclei was 2 cm in diameter, the
atom would have a diameter twice the
length of a football field
Atomic Symbols
Mass number =
number of protons +
number of neutrons
Charge =
A
Z
Atomic number =
number of protons
Defines the
element
X
Q
Number of protons number of electrons
Atomic Number
The atomic number
• Is specific for each element
• Is the same for all atoms of an element
• Is equal to the number of protons in an atom
• Appears above the symbol of an element
Atomic Number
Symbol
11
Na
Learning Check
State the number of protons in each:
1. A nitrogen atom
A) 5 protons
B) 7 protons
C) 14 protons
2. A sulfur atom
A) 32 protons
C) 6 protons
3. A barium atom
A) 137 protons
B) 16 protons
B) 81 protons
C) 56 protons
Variability in the Number
of Electrons and Neutrons
• Isotopes
– Atoms of the same element (same number of protons) with
different numbers of neutrons
• Ions
– Charged particles that have either lost or gained electrons
– These have the same number of protons and neutrons, but a
number of electrons that differs from the number of protons
Atomic Symbols
Mass number =
number of protons +
number of neutrons
Charge =
A
Z
Atomic number =
number of protons
X
Q
number of protons –
number of electrons
Learning Check
An atom has 14 protons and 20 neutrons.
1. Its atomic number is
A) 14
B) 16
C) 34
B) 16
C) 34
B) Ca
C) Se
2. Its mass number is
A) 14
3. The element is
A) Si
Atomic Symbols
Mass number =
number of protons +
number of neutrons
Charge =
A
Z
Atomic number =
number of protons
X
Q
number of protons –
number of electrons
Using Atomic Symbols to Calculate
Numbers of Subatomic Particles
• How many electrons, neutrons, and protons
are in the following particles?
# protons
40Ca
40Ca2+
14C
12C
#electrons
#neutrons
Learning Check
Write the nuclear symbols for atoms with the
following subatomic particles:
A. 8 p+, 8 n, 8 e-
___________
B. 17p+, 20n, 18e-
___________
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