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2-1
The Components of Matter
Chapter 2
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2-2
Chapter 2: The Components of Matter
2.1 Elements, Compounds, and Mixtures: An Atomic Overview
2.2 The Observations That Led to an Atomic View of Matter
2.3 Dalton’s Atomic Theory
2.4 The Observations That Led to the Nuclear Atom Model
2.5 The Atomic Theory Today
2.6 Elements: A First Look at the Periodic Table
2.7 Compounds: Introduction to Bonding
2.8 Compounds: Formulas, Names, and Masses
2.9 Classification of Mixtures
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2-3
Definitions for Components of Matter
Element - the simplest type of substance with unique physical and
chemical properties. An element consists of only one type of atom. It
cannot be broken down into any simpler substances by physical or
chemical means.
Molecule - a structure that consists of two or
more atoms that are chemically bound together
and thus behaves as an independent unit.
Figure 2.1
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2-4
Compound - a substance
composed of two or more elements
which are chemically combined.
Mixture - a group of two or more
elements and/or compounds that
are physically intermingled.
Definitions for Components of Matter
Figure 2.1
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2-6
The total mass of substances does not change during a chemical
reaction.
reactant 1 + reactant 2 product
total mass total mass=
calcium oxide + carbon dioxide calcium carbonate
CaO + CO2CaCO
3
56.08g + 44.00g 100.08g
Law of Mass Conservation:
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2-7
No matter the source, a particular compound is
composed of the same elements in the same parts
(fractions) by mass.
Calcium carbonate
Analysis by Mass
(grams/20.0g)
Mass Fraction
(parts/1.00 part)
Percent by Mass
(parts/100 parts)
8.0 g calcium
2.4 g carbon
9.6 g oxygen
20.0 g
40% calcium
12% carbon
48% oxygen
100% by mass
0.40 calcium
0.12 carbon
0.48 oxygen
1.00 part by mass
Law of Definite (or Constant) Composition:
Figure 2.2
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2-8
Sample Problem 2.1 Calculating the Mass of an Element in a Compound
PROBLEM: Pitchblende is the most commercially important compound of
uranium. Analysis shows that 84.2 g of pitchblende contains
71.4 g of uranium, with oxygen as the only other element. How
many grams of uranium can be obtained from 102 kg of
pitchblende?
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2-9
If elements A and B react to form two compounds, the different
masses of B that combine with a fixed mass of A can be expressed
as a ratio of small whole numbers.
Example: Carbon Oxides A & B
Carbon Oxide I : 57.1% oxygen and 42.9% carbon
Carbon Oxide II : 72.7% oxygen and 27.3% carbon
Assume that you have 100g of each compound.
In 100 g of each compound: g O = 57.1 g for oxide I & 72.7 g for oxide IIg C = 42.9 g for oxide I & 27.3 g for oxide II
Law of Multiple Proportions:
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Dalton’s Atomic Theory
The Postulates
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Dalton’s Atomic Theory
explains the mass laws
Mass conservation
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2-12
Dalton’s Atomic Theory
explains the mass laws
Definite composition
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2-13
Dalton’s Atomic Theory
explains the mass laws
Multiple proportions
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2-14
Figure 2.4
Experiments to determine the properties of cathode rays.
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Experiments to Determine the Properties of Cathode Rays
OBSERVATION
1. Ray bends in magnetic field.
2. Ray bends towards positive
plate in electric field.
CONCLUSION
consists of charged particles
consists of negative particles3. Ray is identical for any cathode.
particles found in all matter
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2-16
Figure 2.5Millikan’s oil-drop experiment
for measuring an electron’s charge.
(1909)
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Millikan used his findings to also calculate the mass of an
electron.
mass of electron =mass
charge
Xcharge
determined by J.J. Thomson and
others
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Figure 2.6Rutherford’s a-scattering experiment
and discovery of the atomic nucleus.
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Figure 2.7 General features of the atom today.
•The atom is an electrically neutral, spherical entity composed of a positively
charged central nucleus surrounded by one or more negatively charged
electrons.
•The atomic nucleus consists of protons and neutrons.
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2-20
Properties of the Three Key Subatomic Particles
Charge Mass
Relative Absolute(C)* Relative(amu)† Absolute(g)
Location
in the AtomName(Symbol)
Electron (e-)
Neutron (n0)
Proton (p+)
Table 2.2
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2-21 Figure 2.8
Atomic Symbols, Isotopes, Numbers
X =
A =
Isotope =
A
Z
Z =
N =
X The Symbol of the Atom or Isotope
See Laboratory Tools
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Figure 2.9The Mass Spectrometer and Its Data
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Sample Problem 2.2 Determining the Number of Subatomic
Particles in the Isotopes of an Element
PROBLEM: Silicon(Si) is essential to the computer industry as a major
component of semiconductor chips. It has three naturally
occurring isoltopes: 28Si, 29Si, and 30Si. Determine the number
of protons, neutrons, and electrons in each silicon isotope.
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2-24
Sample Problem 2.3 Calculating the Atomic Mass of an Element
PROBLEM: Silver(Ag: Z = 47) has 46 known isotopes, but only two occur
naturally, 107Ag and 109Ag. Given the following mass
spectrometric data, calculate the atomic mass of Ag:
Isotope Mass(amu) Abundance(%)
107Ag
109Ag
106.90509
108.90476
51.84
48.16
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The Modern Reassessment of the Atomic Theory
1. All matter is composed of atoms. The atom is the smallest body that
retains the unique identity of the element.
2. Atoms of one element cannot be converted into atoms of another
element in a chemical reaction. Elements can only be converted
into other elements in nuclear reactions.
3. All atoms of an element have the same number of protons and
electrons, which determines the chemical behavior of the element.
Isotopes of an element differ in the number of neutrons, and thus
in mass number. A sample of the element is treated as though its
atoms have an average mass.
4. Compounds are formed by the chemical combination of two or more
elements in specific ratios.
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Figure 2.10 The modern periodic table.
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Figure 2.11
The formation of an ionic compound.
Transferring electrons from the atoms of one
element to those of another results in an ionic
compound.
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2-28
Figure 2.12 Factors that influence the strength of ionic bonding.
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Sample Problem 2.4 Predicting the Ion and Element Forms
PROBLEM: What monatomic ions do the following elements form?
(a) Iodine (Z = 53) (b) Calcium (Z = 20) (c) Aluminum (Z = 13)
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Formation of a covalent bond between two H atoms.Figure 2.13
Covalent bonds form when elements share electrons, which usually
occurs between nonmetals.
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2-31
Replace w/
Figure 2.14
1eElements that occur as molecules.
1A 2A 3A 4A 5A 6A 7A 8A
(1) (2) (13) (14) (15) (16) (17) (18)
H2
N2 O2 F2
P4 S8 Cl2
Se8 Br2
I2
diatomic molecules tetratomic molecules octatomic molecules
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2-32
A polyatomic ion
Figure 2.15
Elements that are polyatomic.
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Types of Chemical Formulas
An empirical formula indicates the relative number of atoms of
each element in the compound. It is the simplest type of formula.
A molecular formula shows the actual number of atoms of
each element in a molecule of the compound.
A structural formula shows the number of atoms and the
bonds between them, that is, the relative placement and
connections of atoms in the molecule.
A chemical formula is comprised of element symbols and numerical
subscripts that show the type and number of each atom present in the
smallest unit of the substance.
The empirical formula for hydrogen peroxide is HO.
The molecular formula for hydrogen peroxide is H2O2.
The structural formula for hydrogen peroxide is H-O-O-H.
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2-34
Figure 2.16 Some common monatomic ions of the elements.
Can you see any patterns?
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2-35
Common Monoatomic IonsTable 2.3
H- hydride
Na+ sodium
H+ hydrogen
Li+ lithium fluorideF-
Cs+ cesium
K+ potassium
Ag+ silver
chlorideCl-
bromideBr-
iodideI-
Mg2+ magnesium
Sr2+ strontium
Ca2+ calcium
Zn2+ zinc
Ba2+ barium
Cd2+ cadmium
Al3+ aluminum
+1
+2
+3
Cations
Charge Formula Name
Anions
Charge Formula Name
-1
-2
-3
oxideO2-
sulfideS2-
nitrideN3-
Common ions are in blue.
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Naming binary ionic compounds
The name of the cation is the same as the name of the metal.
Many metal names end in -ium.
The name of the anion takes the root of the nonmetal name
and adds the suffix -ide.
Calcium and bromine form calcium bromide.
The name of the cation is written first, followed by that of the anion.
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Sample Problem 2.5 Naming Binary Ionic Compounds
PROBLEM: Name the ionic compound formed from the following pairs of
elements:
(a) magnesium and nitrogen (b) iodine and cadmium
(c) strontium and fluorine (d) sulfur and cesium
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Sample Problem 2.6 Determining Formulas of Binary Ionic Compounds
PROBLEM: Write empirical formulas for the compounds named in Sample
Problem 2.5.
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Metals With Several Oxidation States
Element
Table 2.4 (partial)
Ion Formula Systematic Name Common Name
Copper Cu+1
Cu+2
copper(I)
copper(II)
cuprous
cupric
CobaltCo+2
Co+3
cobalt(II)
cobalt (III)
ferrous
Iron
Fe+2 iron(II)
Fe+3 iron(III) ferric
ManganeseMn+2 manganese(II)
Mn+3 manganese(III)
TinSn+2 tin(II)
Sn+4 tin(IV)
stannous
stannic
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Sample Problem 2.7 Determining Names and Formulas of Ionic
Compounds of Elements That Form More
Than One Ion
PROBLEM: Give the systematic names for the formulas or the formulas for
the names of the following compounds:
(a) tin(II) fluoride (b) CrI3
(c) ferric oxide (d) CoS
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Some Common Polyatomic Ions
Formula
Cations
NH4+
Common Anions
H3O+
Formula
ammonium hydronium
Name Name
CH3COO- acetate
CN- cyanide
OH- hydroxide
ClO3- chlorate
NO2- nitrite
NO3- nitrate
MnO4- permanganate
CO3-2 carbonate
CrO4-2 chromate
Cr2O7-2 dichromate
O2-2 oxide
SO4-2 sulfate
PO4-3 phosphate
Table 2.5 (partial)
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Naming oxoanions
Prefixes Root Suffixes Examples
rootper ate ClO4- perchlorate
ateroot ClO3- chlorate
iteroot ClO2- chlorite
itehypo root ClO- hypochlorite
No
. o
f O
ato
ms
Figure 2.17
Numerical Prefixes for Hydrates and Binary Covalent Compounds
Number Prefix Number Prefix Number Prefix
1 mono
2 di
3 tri
4 tetra
5 penta
6 hexa
7 hepta
8 octa
9 nona
10 deca
Table 2.6
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2-43
Sample Problem 2.8 Determining Names and Formulas of Ionic
Compounds Containing Polyatomic Ions
PROBLEM: Give the systematic names or the formula or the formulas for the
names of the following compounds:
(a) Fe(ClO4)2(b) sodium sulfite (c) Ba(OH)2 8H2O
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2-44
Sample Problem 2.9 Recognizing Incorrect Names and Formulas
of Ionic Compounds
PROBLEM: Something is wrong with the second part of each statement.
Provide the correct name or formula.
(a) Ba(C2H3O2)2 is called barium diacetate.
(b) Sodium sulfide has the formula (Na)2SO3.
(c) Iron(II) sulfate has the formula Fe2(SO4)3.
(d) Cesium carbonate has the formula Cs2(CO3).
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2-45
Naming Acids
1) Binary acids solutions form when certain gaseous compounds
dissolve in water.
For example, when gaseous hydrogen chloride(HCl) dissolves in
water, it forms a solution called hydrochloric acid. Prefix hydro- +
anion nonmetal root + suffix -ic + the word acid - hydrochloric acid
2) Oxoacid names are similar to those of the oxoanions, except for
two suffix changes:
Anion “-ate” suffix becomes an “-ic” suffix in the acid. Anion “-ite”
suffix becomes an “-ous” suffix in the acid.
The oxoanion prefixes “hypo-” and “per-” are retained. Thus, BrO4-
is perbromate, and HBrO4 is perbromic acid; IO2- is iodite, and
HIO2 is iodous acid.
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2-46
Sample Problem 2.10 Determining Names and Formulas of Anions
and Acids
PROBLEM: Name the following anions and give the names and formulas of
the acids derived from them:
(a) Br - (b) IO3- (c) CN - (d) SO4
2- (e) NO2-
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2-47
Sample Problem 2.11 Determining Names and Formulas of Binary
Covalent Compounds
SOLUTION:
PROBLEM: (a) What is the formula of carbon disulfide?
(c) Give the name and formula of the compound whose
molecules each consist of two N atoms and four O atoms.
(b) What is the name of PCl5?
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2-48
Sample Problem 2.12 Recognizing Incorrect Names and Formulas
of Binary Covalent Compounds
(a) SF4 is monosulfur pentafluoride.
(c) N2O3 is dinitrotrioxide.
(b) Dichlorine heptaoxide is Cl2O6.
PROBLEM: Explain what is wrong with the name of formula in the second
part of each statement and correct it:
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Sample Problem 2.13 Calculating the Molecular Mass of a Compound
(a) tetraphosphorous trisulfide (b) ammonium nitrate
PROBLEM: Using the data in the periodic table, calculate the molecular (or
formula) mass of the following compounds:
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2-50
Sample Problem 2.14 Determining Formulas and Names from Molecular
Depictions
PROBLEM: Each box contains a representation of a binary compound.
Determine its formula, name, and molecular (formula) mass.
(a) (b)
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Allowed to react chemically
therefore cannot be separated by
physical means.
Figure 2.19 The distinction between mixtures and compounds.
S
Fe
Physically mixed therefore can be
separated by physical means; in
this case by a magnet.