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The Components of Matter

Chapter 2


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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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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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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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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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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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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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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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explains the mass laws

Mass conservation


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Definite composition


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Multiple proportions


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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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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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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


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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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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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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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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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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Figure 2.16 Some common monatomic ions of the elements.

Can you see any patterns?


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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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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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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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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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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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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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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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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.


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Mixtures

Heterogeneous mixtures :

Homogeneous mixtures :

Solutions :

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Chapter 2 - slcchemistry.files.wordpress.com · cannot be broken down into any simpler substances by physical or chemical means. Molecule - a structure that consists of two or more