copyright © by houghton mifflin company. all rights reserved. chapter 2 atoms, molecules, and ions

Copyright © by Houghton Mifflin Company. All rights reserved.

Chapter 2

Atoms, Molecules, and Ions


What is atom?

Electron

Nucleus

Atomic Structure

Copyright © Cengage Learning. All rights reserved 3

Greeks were the first to attempt to explain why chemical changes occur.

Alchemy dominated for 2000 years. Several elements discovered. Mineral acids prepared.

Robert Boyle was the first “chemist”. Performed quantitative experiments. Developed first experimental definition of an

element.

Early History of Chemistry


The Discovery of Electrons

J.J. Thomson –CRT experiment

Robert Millikan – Oil droplets experiment


Early Experiments to Characterize the atom

Measurement of electron

J.J. Thomson (1856-1940)

Cathode-ray tube experiment (1898-1903)

e/m = -1.76× 108 C/g

J. J. Thomson (1898—1903) Postulated the existence of negatively charged

particles, that we now call electrons, using cathode-ray tubes.

Determined the charge-to-mass ratio of an electron.

The atom must also contain positive particles that balance exactly the negative charge carried by electrons.



Cathode-ray tube


Deflection of rays


Plum-pudding model



Measurement of electron weight

Robert Millikan (1868-1953)

Nobel Prize in Physics in 1923

Oil droplets experiment (1909) m = 9.11X 10-31 Kg



Ernest Rutherford (1871-1937)

Nobel Prize in Chemistry in 1908


The Results from Rutherford The majority of a particles penetrated the foil

undeflected.(穿透 ) Some particles experienced slight deflections.

(小角度偏折 ) A few (about one in every 20000) suffered rather

serious deflections as they penetrated the foil.

(嚴重偏折 ) A similar number did not pass through the foil at

all but “bounced back” in the direction from which they had come.(反彈 )


Thomson’s model Rutherford’s model


The Model of Rutherford Most of the mass and all of the positive charge of an

atom are centered in a very small region called the nucleus. (原子重量集中於一個小區域 )

The atom is mostly empty space. The magnitude of the positive charge is different for

different atoms and is approximately one half the atomic weight of the element.(正電荷重量為原子的1/2)

There exist as many electrons outside the nucleus as there are units of positive charge on the nucleus. The atom as a whole is electrically neutral.(原子為電中性 )

Henri Becquerel (1896)

Discovered radioactivity by observing the spontaneous emission of radiation by uranium.

Nobel Prize in Physics in 1903 Three types of radioactive emission exist:

Gamma rays (ϒ) – high energy light Beta particles (β) – a high speed electron Alpha particles (α) – a particle with a 2+ charge



Founder of Radioactivity

Marie Sklodowska Curie ( Poland 1867-1934)

Found new element polonium (Po 釙 ) in 1898

Nobel Prize in Physics in 1903

Found new element radium (Ra 鐳 ) in 1898

Nobel Prize in chemistry in 1911


Modern View of Atomic Structure


Isotopes of Elements

Isotopes are identified by: Atomic Number (Z) – number of protons Mass Number (A) – number of protons plus

number of neutrons



Components of Atoms in Physics

　電量電子家族緲子家族陶子家族

夸克(quark

)

+2/3上夸克 u (up quark)

m ～ 0.01GeV

魅夸克 c (charm quark)m ～ 1.5GeV

頂夸克 t (top quark)

m ＞ 89GeV

-1/3下夸克 d

(down quark)m ～ 0.01GeV

奇夸克 s (strange quark)m ～ 0.15GeV

底夸克 b (bottom quark)m ～ 5.5GeV

輕子(lepton

)

0電子微中子 v

(electron neutrino)m ＜ 2×10-8GeV

緲子微中子v(muon neutrino)

m ＜ 2×10 －

4GeV

陶子微中子 v(tau

neutrino)m ＜ 0.035GeV

-1電子 e (electron)

m ＝ 5.11×10-4

GeV

緲子 ν(muon)m ＝ 0.106GeV

陶子 τ(tau)m ＝ 1.75GeV


Naming Simple Compounds

Binary Compounds (Type I; Ionic)

Binary Compounds (Type II; Ionic)

Binary Compounds (Type III; Contain Two Nonmetals)


Binary Compounds (Type I; Ionic)

Rules1. The cation is always named first and anion

second.

2. A monatomic cation takes its name from the name of element.

3. A monatomic anion is named by taking the first part of the element name and adding –ide.


Naming Compounds For Type I

1. NaCl

2. NaH

3. KI

4. MgO

5. BN

Binary Ionic Compounds (Type II) Metals in these compounds form more than one type of

positive ion. Charge on the metal ion must be specified. Roman numeral indicates the charge of the metal

cation. Transition metal cations usually require a Roman

numeral. Elements that form only one cation do not need to be

identified by a roman numeral.



Ion Systematic Name

Fe+3 Iron(III)

Fe+2 Iron(II)

Cu+2 Copper(II)

Cu+ Copper(I)

Co+3 Cobalt(III)

Co+2 Cobalt(II)

Sn+4 Tin(IV)

Sn+2 Tin(II)

Pb+4 Lead(IV)

Pb+2 Lead(II)



Rules for Polyatomic Ions

1. Contain polyatomic ions. ex. NH+4, CN-, SO4

-2

2. Polyatomic ions are assigned special names that must be memorized to name the compounds.3. For oxyanions, the name of the one with the smaller number of oxygen atoms ends in –ite, and the name of the one with the larger number of oxygen atoms ends in –ate4. When more than two oxyanions make up a series, hypo- (less than) for fewest oxygen atoms and per- (more than) for the most oxygen atoms are used.



CoBr2

CaCl2Al2O3

CrCl3


Binary Compounds (Type III; Contain Two Nonmetals)

Rules

1. The first element in the formula is named first,

using the full element name.

2. The second element is named as if it was an

anion.

3. Prefixes are used to denote the numbers of

atoms.

4. The prefix mono- is never used for naming the

first element.


Prefix Number Indicated

Mono- 1

Di- 2

Tri- 3

Tetra- 4

Penta 5

Hexa- 6

Hepta- 7

Octa- 8

Nona- 9

Deca- 10


Problems for naming

CuI NaClO4

SF2

Mg(OH)2

Ag2CrO4

Li3N


Question

Which is not the correct chemical formula for the compound named? potassium phosphate, K3PO4 iron(II) oxide, FeO calcium carbonate, CaCO3 sodium sulfide, NaS lithium nitrate, LiNO3


Answer

d) sodium sulfide, NaS

Sodium sulfide is a binary compound composed of a Group 1 element, whose charge in compounds is +1, and a Group 16 element, whose charge in binary compounds is commonly –2. This means that two sodium ions must be combined with one sulfide ion to form a neutral compound.


Question

Which of the following is not the correct chemical formula for the compound named? Li2O, lithium oxide

FePO4, iron(III) phosphate HF, hydrogen fluoride BaCl2, barium dichloride

Mg3N2, magnesium nitride


Answer

d) BaCl2, barium dichloride

The binary compound, BaCl2, is composed of a metal and a nonmetal. Its correct name is barium chloride (no prefix is needed).


Question

Which is the correct formula for copper(I) sulfide? CuS Cu2S

CuS2

Cu2S2

None of the above


Answer

b) Cu2S

The copper(I) ion has a +1 charge and the sulfide ion has a –2 charge.


Question

What is the correct name for this compound with the formula Mg3(PO4)2? Trimagnesium diphosphate Magnesium(II) phosphate Magnesium phosphate Magnesium(II) diphosphate Magnesium(III) diphosphate


Answer

c) Magnesium phosphate

The magnesium ion has a +2 charge and the phosphate ion has a –3 charge.

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