Download Chapter 1: The Mole

Chapter 1
Elements and Compounds
Measurements and observations are made in
the macroscopic world. We interpret these
measurements and observations using the
microscopic world. Chemistry is involved in
both worlds.
Chemistry: A Definition
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Find patterns
Develop models
Make predictions
Be quantitative
Experimental testing
Elements, Compounds and Mixtures
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Elements
Compounds
Mixtures
Homogeneous
Heterogeneous
Atomic Symbols
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Shorthand notation
Some derived from English names.
Bi for bismuth.
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Others derived from non-English names.
Fe for iron.
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Upper and lower case important.
CO and Co are different.
Chemical Formula
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Atomic symbols and subscripts
Compounds
Molecular
Ionic
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Molecular elements
e. g. O2, H2
Evidence for the Existence of Atoms
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Dalton’s Atomic Theory
Indestructible atoms
Elemental identity
Elemental distinction
Atomic combination
The Role of Measurement in
Chemistry
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Scientific Knowledge
Products
Processes
The Role of Measurement in
Chemistry
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Measurements
Numbers and units
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Scientific notation
SI and other units
Prefixes
Conversion factors
The Structure of Atoms
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Beyond Dalton’s Theory
Three subatomic particles that are
important for chemists:
Electron
Proton
Neutron
The Structure of Atoms
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Absolute vs Relative Charges
Electron charge = Proton charge (with the
sign reversed).
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Nucleus holds the protons and neutrons.
Atomic Number and Mass Number
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Both positive integers.
Mass Number (A)  Atomic Number (Z)
Z = number of protons.
A = Z + number of neutrons.
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X is Atomic Symbol.
A
Z
X
Isotopes
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Same Z
Different A
Identical chemistry
A1
Z1
X
A2
Z1
X
Isotopes
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Some elements have only one.
Some elements have a few.
Some elements have many.
% natural abundance is the percentage of
atoms occurring as a given isotope.
Isotopes
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Mass of an atom
Absolute mass
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Uses a mass unit: gram, ounce, …
Rarely used
Relative mass
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Relative to specific isotope of carbon
By convention 12C = 12.00000... amu
Ratio called atomic mass.
Used frequently: amu
The Difference Between Atoms and
Ions
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Atoms are neutral.
Ions are charged.
Positively charged ions: cations.
Negatively charged ions: anions.
Polyatomic Ions
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Many polyatomic anions.
A few polyatomic cations.
Polyatomic ions
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Spelling
Chemical Formula
Charge
Table 1.6
The Periodic Table
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Atomic number
Groups
Periods
Figure 1.8
The Periodic Table
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Metals
Nonmetals
Semimetals (metalloids)
Important to know where an element is
situated in the periodic table.
The Macroscopic, Atomic and
Symbolic Worlds of Chemistry
Figure 1.9
The Mass of an Atom
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Average masses reported.
Average masses are weighted averages.
amu used.
Chemical Reactions and the Law of
Conservation of Atoms
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Fundamental law of chemistry:
Conservation of Mass
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What does it mean?
In a chemical reaction, matter is neither
created nor destroyed.
Chemical Reactions and the Law of
Conservation of Atoms
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Established empirically.
May not be true, but no counter example
has ever been found.
Atomic model based on this law.
Example of scientific method.
Chemical Equations as a
Representation of Chemical
Reactions
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Heart of Chemistry
Chemical formulas used.
An arrow is used to separate reactants and
products.
Phase information is sometimes included.
Equation carries no implication as to how
fast the reaction occurs.
Chemical Equations as a
Representation of Chemical
Reactions
Reactants → Products
2Mg(s) + O2(g) → 2MgO(s)
Balancing Chemical Equations
Notice the equation did not read
Mg(s) + O2(g) → MgO(s).
Why not?
Balancing Chemical Equations
Notice the equation did not read
Mg(s) + O2(g) → MgO(s).
Why not?
Chemical equations must be balanced.