Ch02 Lecture PPT

7/30/2019 Ch02 Lecture PPT

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Chapter 2

Atoms, Molecules,

and Ions

John D. Bookstaver

St. Charles Community College

Cottleville, MO

Lecture Presentation

2012 Pearson Education, Inc.


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Atoms,

Molecules,

and Ions 2012 Pearson Education, Inc.

Atomic Theory of Matter

The theory that

atoms are thefundamental

building blocks

of matter

reemerged in

the earlynineteenth

century,

championed

by John

Dalton.


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Atoms,

Molecules,


Dalton's Postulates

Each element is

composed of extremely

small particles calledatoms.


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Atoms,

Molecules,


Dalton's Postulates

All atoms of a given

element are identical to

one another in massand other properties,

but the atoms of one

element are different

from the atoms of allother elements.


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Atoms,

Molecules,


Dalton's Postulates

Atoms of an element

are not changed into

atoms of a differentelement by chemical

reactions; atoms are

neither created nor

destroyed in chemicalreactions.


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Atoms,

Molecules,


Dalton's Postulates

Compounds areformed when atoms ofmore than one elementcombine; a givencompound always hasthe same relativenumber and kind of

atoms.


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Atoms,

Molecules,


Law of Conservation of MassThe total mass of substances present at the

end of a chemical process is the same as the

mass of substances present before the

process took place.

The law of constant composition

The law of multiple proportions

The law of conservation of energy


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Atoms,

Molecules,

and Ions

Practice Questions

1) Which one of the following is not one of the postulates of Dalton's atomic theory?

A) Atoms are composed of protons, neutrons, and electrons.

B) All atoms of a given element are identical; the atoms of different elements aredifferent and have different properties.

C) Atoms of an element are not changed into different types of atoms by chemical

reactions: atoms are neither created nor destroyed in chemical reactions.

D) Compounds are formed when atoms of more than one element combine; a given

compound always has the same relative number and kind of atoms.

E) Each element is composed of extremely small particles called atoms.

2) Consider the following selected postulates of Dalton's atomic theory:

(i) Each element is composed of extremely small particles called atoms.

(ii) Atoms are indivisible.

(iii) Atoms of a given element are identical.

(iv) Atoms of different elements are different and have different properties.

Which of the postulates is(are) no longer considered valid?

A) (i) and (ii) B) (ii) only C) (ii) and (iii)

D) (iii) only E) (iii) and (iv)


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a.

A. the law of conservation of matterB. the law of multiple proportions

C. the law of constant composition

D. the law of conservation of grams


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b.

A. The second compound must have twice as many oxygen

atoms per carbon atom as the first compound.

B. The second compound must have half as many oxygen

atoms per carbon atom as the first compound.

C. The second compound contains half as many carbon atoms

as the first compound.

D. The first compound contains half as many carbon atoms as

the second compound.


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Atoms,

Molecules,


The Electron

Streams of negatively charged particles were found to

emanate from cathode tubes, causing fluorescence.

J. J. Thomson is credited with their discovery (1897).


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Atoms,

Molecules,


The Electron

Thomson measured the charge/mass ratio ofthe electron to be 1.76 108 coulombs/gram(C/g).


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Atoms,

Molecules,


Millikan Oil-Drop Experiment

Once the charge/mass

ratio of the electron

was known,determination of either

the charge or the mass

of an electron would

yield the other.


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Atoms,

Molecules,


Millikan Oil-Drop Experiment

Robert Millikan

(University of Chicago)

determined the charge

on the electron in

1909.


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Atoms,

Molecules,


Radioactivity

Radioactivity is the spontaneous emission of

radiation by an atom.

It was first observed by Henri Becquerel. Marie and Pierre Curie also studied it.


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Atoms,

Molecules,


Radioactivity

Three types of radiation were discovered byErnest Rutherford: particles

particles

rays


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Atoms,

Molecules,


The Atom, circa 1900

The prevailing theory

was that of the plum

pudding model, putforward by Thomson.

It featured a positive

sphere of matter with

negative electronsimbedded in it.


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Atoms,

Molecules,


Discovery of the Nucleus

Ernest

Rutherford shot

particles at athin sheet of

gold foil and

observed the

pattern of scatterof the particles.


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Atoms,

Molecules,


The Nuclear Atom

Since some particles

were deflected at

large angles,

Thomsons model

could not be correct.


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Atoms,

Molecules,


The Nuclear Atom

Rutherford

postulated a very

small, densenucleus with the

electrons around the

outside of the atom.

Most of the volumeof the atom is empty

space.


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Atoms,

Molecules,


Other Subatomic Particles

Protons were discovered by Rutherford in

1919.

Neutrons were discovered by James

Chadwick in 1932.


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Atoms,

Molecules,


Subatomic Particles

Protons and electrons are the only particles that

have a charge.

Protons and neutrons have essentially the same

mass. The mass of an electron is so small we ignore it.


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Atoms,

Molecules,

and Ions

Practice Problems

1) Which statement below correctly describes the responses of alpha, beta, and gamma

radiation to an electric field?

A) Both beta and gamma are deflected in the same direction, while alpha shows no response.

B) Both alpha and gamma are deflected in the same direction, while beta shows no response.

C) Both alpha and beta are deflected in the same direction, while gamma shows no response.

D) Alpha and beta are deflected in opposite directions, while gamma shows no response.

E) Only alpha is deflected, while beta and gamma show no response.

2) The charge on an electron was determined in the __________.

A) cathode ray tube, by J. J. Thompson B) Rutherford gold foil experiment

C) Millikan oil drop experiment D) Dalton atomic theory

E) atomic theory of matter

3) __________-rays consist of fast-moving electrons.

A) Alpha B) Beta C) Gamma

D) X E) none of the above


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Atoms,

Molecules,

and Ions

Practice Problems4) The gold foil experiment performed in Rutherford's lab __________.

A) confirmed the plum-pudding model of the atom

B) led to the discovery of the atomic nucleus

C) was the basis for Thomson's model of the atom

D) utilized the deflection of beta particles by gold foil

E) proved the law of multiple proportions

5) In the Rutherford nuclear-atom model, __________.

A) the heavy subatomic particles, protons and neutrons, reside in the nucleusB) the three principal subatomic particles (protons, neutrons, and electrons) all have essentially

the same mass

C) the light subatomic particles, protons and neutrons, reside in the nucleus

D) mass is spread essentially uniformly throughout the atom

E) the three principal subatomic particles (protons, neutrons, and electrons) all have essentially

the same mass and mass is spread essentially uniformly throughout the atom

6) Cathode rays are __________.

A) Neutrons B) x-rays C) electrons

D) Protons E) atoms


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Atoms,

Molecules,


Symbols of Elements

Elements are symbolized by one or two

letters.


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Atoms,

Molecules,


Symbols of Elements

All atoms of the same element have the same

number of protons, which is called the atomic

number, Z.


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Atoms,

Molecules,


Symbols of Elements

The mass of an atom in atomic mass units

(amu) is the total number of protons and

neutrons in the atom.


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Atoms,

Molecules,


Isotopes

Isotopes are atoms of the same element with

different masses.

Isotopes have different numbers of neutrons.


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Atoms,

Molecules,


Atomic Mass

Atomic and

molecular masses

can be measuredwith great accuracy

using a mass

spectrometer.


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Atoms,

Molecules,


Average Mass

Because in the real world we use large

amounts of atoms and molecules, we use

average masses in calculations. Average mass is calculated from the

isotopes of an element weighted by their

relative abundances.


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Atoms,

Molecules,

and Ions

Practice Problems1) There are __________ electrons, __________ protons, and __________ neutrons in an atom

of .

A) 132, 132, 54 B) 54, 54, 132 C) 78, 78, 54

D) 54, 54, 78 E) 78, 78, 132

2) An atom of the most common isotope of gold, 197Au, has __________ protons, __________

neutrons, and __________ electrons.

A) 197, 79, 118 B) 118, 79, 39 C) 79, 197, 197

D) 79, 118, 118 E) 79, 118, 79

3) Which combination of protons, neutrons, and electrons is correct for the isotope of copper ,

A) 29 p+, 34 n, 29 e- B) 29 p+, 29 n, 63 e-

C) 63 p+, 29 n, 63 e- D) 34 p+, 29 n, 34 e-

E) 34 p+, 34 n, 29 e-

4) Which isotope has 45 neutrons?

A) Kr B) Br C) Se D) Cl E) Rh


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Atoms,

Molecules,

and Ions

Practice Problems5) The element X has three naturally occurring isotopes. The isotopic masses (amu) and %

abundances of the isotopes are given in the table below. The average atomic mass of the

element is __________ amu.

6) An unknown element is found to have three naturally occurring isotopes with atomic masses

of 35.9675 (0.337%), 37.9627 (0.063%), and 39.9624 (99.600%). Which of the following is the

unknown element?

A) Ar

B) K

C) Cl

D) Ca

E) None of the above could be the unknown element.


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Atoms,

Molecules,


Periodic Table

The periodic

table is a

systematic catalogof the elements.

Elements are

arranged in order

of atomic number.


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Atoms,

Molecules,


Periodic Table

The rows on the

periodic chart are

periods.

Columns aregroups.

Elements in the

same group have

similar chemical

properties.


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Atoms,

Molecules,


Periodicity

When one looks at the chemical properties of

elements, one notices a repeating pattern ofreactivities.


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Atoms,

Molecules,


Groups

These five groups are known by their names.


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Atoms,

Molecules,


Periodic Table

Nonmetals are

on the right side

of the periodictable (with the

exception of H).


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Atoms,

Molecules,


Periodic Table

Metalloids

border the

stair-step line

(with the

exception of Al,

Po, and At).


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Atoms,

Molecules,


Periodic Table

Metals are on

the left side of

the chart.


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Atoms,

Molecules,


Chemical Formulas

The subscript to the rightof the symbol of an

element tells the number

of atoms of that element

in one molecule of thecompound.


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Atoms,

Molecules,


Chemical Formulas

Molecular compoundsare composed of

molecules and almost

always contain only

nonmetals.


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Atoms,

Molecules,


Diatomic Molecules

These seven elements occur naturallyas molecules containing two atoms:

Hydrogen

Nitrogen

Oxygen

Fluorine

Chlorine Bromine

Iodine


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Atoms,

Molecules,


Types of Formulas

Empirical formulas give the lowest whole-

number ratio of atoms of each element in a

compound. Molecular formulas give the exact number

of atoms of each element in a compound.


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Atoms,

Molecules,


Types of Formulas

Structural formulas show

the order in which atoms are

bonded. Perspective drawings also

show the three-dimensional

array of atoms in a

compound.


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Atoms,

Molecules,


Ions

When atoms lose or gain electrons, they

become ions.

Cations are positive and are formed by elements

on the left side of the periodic chart.

Anions are negative and are formed by elements

on the right side of the periodic chart.


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Atoms,

Molecules,


Ionic Bonds

Ionic compounds (such as NaCl) aregenerally formed between metals and

nonmetals.


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Atoms,

Molecules,


Writing Formulas

Because compounds are electrically neutral,

one can determine the formula of a

compound this way: The charge on the cation becomes the subscript

on the anion.

The charge on the anion becomes the subscript

on the cation.

If these subscripts are not in the lowest whole-

number ratio, divide them by the greatest common

factor.


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Atoms,

Molecules,


Common Cations


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Atoms,

Molecules,


Common Anions


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Atoms,

Molecules,

and Ions

Practice Problems

1) There are __________ protons, __________ neutrons, and __________ electrons in 131I-.

2) There are __________ protons, __________ neutrons, and __________ electrons in 238U+5.

3) Which species has 48 electrons?

4) What is the formula of the compound formed between strontium ions and nitrogen ions?

A) SrN B) Sr3N2 C) Sr2N3 D) SrN2 E) SrN3

5) Magnesium reacts with a certain element to form a compound with the general formula MgX.

What would the most likely formula be for the compound formed between potassium and

element X?

A) K2X B) KX2 C) K2X3 D) K2X2 E) KX


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2012 Pearson Education, Inc.

Practice Problems

Which of the formulas below does not represent acompound that actually exists?

a. CaCO3

b. H2O2

c. KMnO4

d. Na2PO

3


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Atoms,

Molecules,


Inorganic Nomenclature

Write the name of the cation.

If the anion is an element, change itsending to -ide; if the anion is a polyatomicion, simply write the name of thepolyatomic ion.

If the cation can have more than onepossible charge, write the charge as aRoman numeral in parentheses.


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Atoms,

Molecules,


Patterns in Oxyanion Nomenclature

When there are two oxyanions involving the

same element:

The one with fewer oxygens ends in -i te. The one with more oxygens ends in -ate.

NO2 : nitrite; SO32 : sulfite

NO3

: nitrate; SO42

: sulfate


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Atoms,

Molecules,



Central atoms on the second row have bond

to at most three oxygens; those on the thirdrow take up to four.

Charges increase as you go from rightto left.


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Atoms,

Molecules,



The one with the second fewest oxygens ends in -i te.

ClO2 : chlorite

The one with the second most oxygens ends in -ate.

ClO3

: chlorate


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Atoms,

Molecules,



The one with the fewest oxygens has the prefixhypo- and ends in -i te.

ClO: hypochlorite

The one with the most oxygens has the prefix

per- and ends in -ate.

ClO4: perchlorate


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Atoms,

Molecules,


Acid Nomenclature

If the anion in the acid

ends in -ide, change

the ending to -ic acid

and add the prefixhydro- .

HCl: hydrochloric acid

HBr: hydrobromic acid

HI: hydroiodic acid


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Atoms,

Molecules,


Acid Nomenclature


ends in -i te, change the

ending to -ous acid.

HClO: hypochlorous acid HClO2: chlorous acid


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Atoms,

Molecules,


Acid Nomenclature


ends in -ate, change

the ending to -ic acid.

HClO3: chloric acid HClO4: perchloric acid


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Atoms,

Molecules,


Nomenclature of Binary Compounds

The less electronegativeatom is usually listed first.

A prefix is used to denotethe number of atoms ofeach element in thecompound (mono- is notused on the first element

listed, however) .


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Atoms,

Molecules,



The ending on the more

electronegative element

is changed to -ide.

CO2: carbon dioxide

CCl4: carbon tetrachloride


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Atoms,

Molecules,



If the prefix ends with aoro and the name of theelement begins with a

vowel, the twosuccessive vowels areoften elided into one.

N2O5: dinitrogen pentoxide


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Atoms,

Molecules,


Nomenclature of Organic Compounds

Organic chemistry is the study of carbon.

Organic chemistry has its own system ofnomenclature.


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Atoms,

Molecules,



The simplest hydrocarbons (compoundscontaining only carbon and hydrogen) arealkanes.


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Atoms,

Molecules,



The first part of the names just listed

correspond to the number of carbons(meth-= 1, eth-= 2, prop-= 3, etc.).


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Atoms,

Molecules


When a hydrogen in an alkane is replaced with

something else (a functional group, like -OH in

the compounds above), the name is derived fromthe name of the alkane.

The ending denotes the type of compound.

An alcohol ends in -ol

Ch02 Lecture PPT

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