The Components of Matter · 2010-08-30 · Atomic Weight ¾For elements with more than one isotope, the atomic weight reported in the periodic table represents a weighted average

8/30/2010

1

The Components of MatterChapter 2

Element, Atom, Compound, and Molecule

CHEMICAL ELEMENTS - pure substances that cannot be decomposed by ordinary means to other substances.

An ATOM is the smallest particle of an element that has the chemical properties of the element. c e ca p ope t es o t e e e e t.

CHEMICAL COMPOUNDS are composed of two or more kinds of atoms and so can be decomposed to those atoms.

A MOLECULE is the smallest unit of a compound that retains the chemical characteristics of the compound.

Elements, Compounds, and MixturesMolecule: two or more atoms join together chemically. Example: H2, H2O, CO2, C6H6, O2, Cl2, C2H6O

Compound: Molecule that contains at least two different elements.

Example: H2O, CO2, C6H6, C2H6O

8/30/2010

2

Sample Problem

Postulates of Dalton’s Atomic Theory (1808)

All matter is made of atoms

All atoms of a given element are identical

Compounds are formed by a combination of two or more p ydifferent kinds of atoms

A chemical reaction is arrangement of atoms present in the reacting substances

Atoms are indivisible and indestructible. Atoms cannot be created or converted to other atom types

Three Laws

1. Mass Conservation: Total mass of substances does not change in a reaction

180 g of glucose +

192 g of oxygen gas

264 g of carbon dioxide +

108 g of water

8/30/2010

3

Three Laws

2. Definite Composition: The components of a compound is the same irrespective of the source of the compound

Calcium Carbonate: Made up of calcium, oxygen, and carbon in constant proportion of mass

i.e. 40% calcium, 12% carbon and 48% oxygen

Three Laws

3. Multiple Proportion: If A and B reacts to form two compounds, the masses of B that combines with a fixed mass of A in the two compounds can be expressed as a ratio of small whole number

Consider two compounds

Carbon oxide I Carbon oxide II--------------------------------------------------------------------

g of oxygen/100 g compound 57.1 72.7g of carbon/100 g compound 42.9 27.3

g of oxygen/g of carbon 1.33 2.66

Ratio of ‘g of oxygen/g of carbong of oxygen/g of carbon’ in compound II and compound I is “2”

Electricity and Radioactivity

Objects can bear an electric chargeTwo types of charges- positive and negativeSubatomic particles?

Marie Curie suggested that atoms of certain substances emit rays when they disintegrate. (1898)These are radioactive materials like uranium, polonium, radium.

Contradicted Dolton’s idea that atoms are indivisible

234U → 230Th + 4He92 90 2

(alpha-ray)

8/30/2010

4

Evidence for Sub-atomic ParticlesThomson experiments with Cathode-Ray Tubes (1897)

Discovery of The Electrons

Cathode rays: beam of negatively charged particle known as electrons

By balancing the effects of the electrical and magnetic fields, the charge/mass (e/m) ratio was determined for the electronelectron

Same charge/mass ratio in experiments using 20 different metals as cathodes and several different gasses

Electrons are present in atoms of all elements!!

Millikan’s Oil Drop Experiment Determination of Charge of an Electron

By balancing the electrostatic attractive and gravitation forces,electron charge (-1.60 x 10-19C) was determined. From e and e/m values, electron mass was calculated (9.109388 x 10-28g)

8/30/2010

5

In 1886, Goldstein, using equipment similar to cathode ray tube, discovered particles with charge equal and opposite to that of electron, but much larger mass

Rutherford later (1911) found these particles to be identical

Evidence for Sub-atomic Particles

to hydrogen atoms minus one electron

Chadwick (1932) discovered particle with similar mass to proton but zero charge

Named these particles protons

Neutron

Properties of Subatomic Particles

Subatomic Particle

Location in Atom

Symbol Mass (grams) Relative Mass

Relative Charge

neutron nucleus n0 1.674927 x 10-24 1 0

proton nucleus p+ 1.672622 x 10-24 1 +1

electron Moving around

outside the nucleus

e- 9.109383 x 10-28 1/1836 -1

Evidence for the nucleus

Three subatomic particles: electron, proton and neutron

How these particles are arranged in an atom?

Thomson’s model of atomic structure: “plum pudding” or “chocolate chip cookie” model

Atoms consisted of negatively charged electrons embedded in a cloud of positive chargeThe negative and positive charges balance and result in the atom being neutral

--

-

-

--

++

+

+

+

+

Electron

Positive charge

8/30/2010

6

Evidence for The Nucleus

In 1911, Geiger and Rutherford studied the interaction of positively charged particles (α-particles) with thin metal foils

If the “plum pudding” hypothesis (model) were true, what would happen to α-particles fired at a metal foil?

--

-

-

--

++

+

+

+

+

Electron

Positive charge

Scattering of α-particles

Scattering of α-particlesObservation…..

“It was about as credible as if you fired a 15-inch shell at a piece of paper and it came back and hit you.” Ernest Rutherford

8/30/2010

7

Scattering of α -particles

Rutherford’s hypothesis:Positive charge concentrated in one tiny region called the nucleus(now known to be about 10-15 m in diameter)Electrons were thought to be distributed throughout the remainder of the atom (10-10 m in diameter)

Inside the Atom

Rutherford also noted that not all the mass of the atom was accounted for by the protons

Chadwick’s neutron

Rutherford proposed a solar system-like model for the yatom

Properties of Subatomic Particles

8/30/2010

8

Inside the Atom

Review:Protons and neutrons contribute nearly all the mass

Protons and neutrons are tightly bound together in the nucleusRadius of nucleus is only 10-5 that of the atomVolume is only 10-15 than of the entire atom

Electrons surround the nucleus as a large “cloud” of negative charge density

Most of the atom’s volume is occupied by electrons

But how are these electrons really arranged around the nucleus?

Atomic and Mass Numbers

Atomic number = The number of protons in the nucleus of an element

Symbolized by the letter Z

Mass number = The total number of protons and neutrons in the

nucleus

Symbolized by the letter A

X is element symbol

A


8/30/2010

9

Na11

23

A Sodium (Na) atom has 11 protons and 12 neutrons. What is the symbol for a sodium atom?

Identify the atomic number, mass number, and number of neutrons of


Identify the atomic number, mass number, and number of neutrons of the following elements:

Z A Number of neutronsC6

12

2963 Cu

82207Pb

IsotopesIndividual atoms have a defined number of protons, electrons and neutrons

What are isotopes?

Atoms of the same element with the same atomic numberbut different mass numbers.

Same number of protons but different number of neutrons

Isotopes

Each element has a characteristic number (and relative abundance) of isotopes

Phosphorus (P) has one naturally occurring isotope with 16 neutrons

C b (C) h h 6 (98 93%

P3115

Also known as phosphorus-31

Carbon (C) has two isotopes, one has 6 neutrons (98.93% abundant), the other has 7 neutrons (1.07% abundant)

Chlorine (Cl) has two isotopes18 neutrons (75.53%)20 neutrons (24.47%)

C126 C13

6Also known as carbon-12

Also known as carbon-13

8/30/2010

10

Relative Masses

The mass of an atom cannot be determined by simply adding up the mass of its constituent protons, neutrons and electrons

Some mass is converted to energy, which is used to hold the nucleus together (binding energy)

d ff l d h h ll b d b d h It is difficult to predict how much mass will be used to bind the nucleus together

Fortunately, the atomic mass of each element can be determined experimentally using very sensitive instruments (mass spectrometer)

Mass Spectrometer

http://www.youtube.com/watch?v=J-wao0O0_qM

Relative MassesFor example the mass of a 12C atom is measured to be 1.9926 x 10-23 g

An exceedingly small number!!!!!!!!!

Rather than work with awkwardly small numbers, atomic masses are converted into more easily handled units

Conversion unit is called the atomic mass unit, μ, μ

By convention, the atomic mass unit is equal to 1/12 the mass of a 12C atom

(1/12)(1.9926 x 10-23g) = 1 μ = 1.6605 x 10-24 gThe atomic mass of 12C is exactly 12 μ

8/30/2010

11

Some Basic Concepts

Atomic MassRelative

Absolute Atomic Mass Mass of a C-atom1.9926 x 10-23 g

12 μ

Converting to bigger Converting to bigger numbersnumbers

Atomic Weight

Mole

12.011

12.011g

Taking contributions Taking contributions of many isotopes of many isotopes and averaging them and averaging them

Amount in grams Amount in grams numerically equal to its numerically equal to its atomic weightatomic weight

Some Basic Concepts1. For the number

of neutrons a. 31b. 15c. 16

P3115

2. The measured atomic mass of a 31P atom is 5.1433 x 10-23 g The converted relative mass is

a. 8.5404 x 10–47

b. 3.2285 x 10–2

c 30 974

1μ = 1.6605 x 10-24 g

d. 46 c. 30.974

3. 1 mole of Phosphorous is a. 8.5404 x 10–47 g

b. 3.2285 x 10–2g

c. 30.974g

1 mole = amount in grams numerically equal to its atomic weight

Atomic Weight

For elements with more than one isotope, the atomic weightreported in the periodic table represents a weighted average of the atomic masses of the naturally occurring isotopes

In other words, it’s the weight of an average atom

For example:3535Cl (75.53 % abundance) has atomic mass = 34.97μ37Cl (24.47 % abundance) has atomic mass = 36.97μ

Atomic weight =

μμμ 35.45100

).97(24.47)(36).97(75.53)(34=

+

8/30/2010

12

Some Basic Concepts

Magnesium: 24Mg (78.99%); 23.9850 μ25Mg (10.00%); 24.9858 μ26Mg (11.01%); 25.9826 μ

3. The atomic weight of magnesium a. 24.3060b. 23.9999c. 24.1096d. 24.9858e. 24.0000

Concept of Mole

How many atoms will be there?Will there be equal number of atoms in all of them?

Concept of Avogadro’s Number

1 mole of any substances will have same number of particles

The magic number is 6.023 ×1023

1 mole of Ca

1 mole of water

6.023 ×1023 6.023 ×1023

1 mole of photons

6.023 ×1023

8/30/2010

13

Concept of Mole

Different mass and volume but each contains 6.022 x 1023 atoms

Mass, Mole, and Atom Conversions

Moles x = gramsgrams

1 molGrams x = moles1 mol

grams

Molar mass of Aluminum = 27.0 g/mol. Determine the mass

of 0.35 mol of Al.


Determine the number of moles of Tin in 36.5 g Tin. Molar mass of Tin = 117.7 g/mol.

Determine the number of atoms in 36.5 g Tin.

8/30/2010

14

Periodic Table of the Elements1 IA

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 VIIIA

1 H

1.008

IIA

IIIA

IVA

VA

VIA

VIIA

2 He4.003

3 Li

6.941

4 Be 9.012

5 B

10.81

6 C

12.011

7 N

14.007

8 O

15.999

9 F

18.998

10 Ne20.179

11 Na 22.990

12 Mg 24.305

IIIB

IVB

VB

VIB

VIIB

[------VIIIB------]

IB

IIB

13 Al

26.982

14 Si

28.086

15 P

30.974

16 S

32.06

17 Cl

35.453

18 Ar

39.94819 K

39 098

20 Ca 40 08

21 Sc

44 956

22 Ti

47 90

23 V

50 942

24 Cr

51 996

25 Mn 54 938

26 Fe

55 847

27 Co 58 933

28 Ni 58 70

29 Cu 63 546

30 Zn 65 38

31 Ga 69 72

32 Ge 72 59

33 As 74 922

34 Se 78 96

35 Br

79 904

36 Kr 83 8039.098 40.08 44.956 47.90 50.942 51.996 54.938 55.847 58.933 58.70 63.546 65.38 69.72 72.59 74.922 78.96 79.904 83.80

37 Rb 85.468

38 Sr 87.62

39 Y

88.906

40 Zr 91.22

41 Nb 92.906

42 Mo 95.94

43 Tc (98)

44 Ru 101.07

45 Rh 102.91

46 Pd 106.4

47 Ag 107.87

48 Cd 112.41

49 In

114.82

50 Sn 118.69

51 Sb 121.75

52 Te

127.60

53 I

126.90

54 Xe

131.3055 Cs 132.91

56 Ba 137.33

57# La

138.91

72 Hf

178.49

73 Ta

180.95

74 W

183.85

75 Re 186.21

76 Os 190.2

77 Ir

192.22

78 Pt

195.09

79 Au 196.97

80 Hg 200.59

81 Tl

204.37

82 Pb 207.2

83 Bi

200.98

84 Po(209)

85 At (210)

86 Rn(222)

87 Fr (223)

88 Ra 226.03

89† Ac 227.03

104 Rf (261)

105 Db (262)

106 Sg (263)

107 Bh (262)

108 Hs (265)

109 Mt (268)

DLC 1o/97

# 58 Ce 140.12

59 Pr

140.91

60 Nd 144.24

61 Pm (145)

62 Sm 150.4

63 Eu 151.96

64 Gd 157.25

65 Tb

158.93

66 Dy 162.50

67 Ho 164.93

68 Er

167.26

69 Tm168.93

70 Yb173.04

71 Lu

174.97

† 90 Th

232.04

91 Pa

231.04

92 U

238.03

93 Np 237.05

94 Pu (244)

95 Am (243)

96 Cm (247)

97 Bk (247)

98 Cf (251)

99 Es (252)

100 Fm (257)

101 Md(258)

102 No(259)

103 Lr (260)

The Periodic Table

Ne

He

8A

Groups: the columns in the periodic table

Elements in the same group have similar chemical properties

Kr

Xe

Rn

Ar

CaK Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Periods: the rows in the periodic table

p

H

Li Be

Na Mg


Ar

Ne

He

F

ClSPSiAl

B C N O

1A

2A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

3A 4A 5A 6A 7A

8AAlkali Metals

Rb

Cs

Fr Ra

Ba

Sr XeITeSbSnInCdAgPdRhRuTcMoNbZrY

La

Ac Rf

Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Db Sg Bh Hs Mt

LuYbTmErHoDyTbGdEuSmPmNdPrCe

Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

8/30/2010

15

H

Li Be

Na Mg


Ar

Ne

He

F

ClSPSiAl

B C N O

1A

2A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

3A 4A 5A 6A 7A

8AAlkaline Earth Metals

Rb

Cs

Fr Ra

Ba


La

Ac Rf


Db Sg Bh Hs Mt



H

Li Be

Na Mg


Ar

Ne

He

F

ClSPSiAl

B C N O

1A

2A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

3A 4A 5A 6A 7A

8AHalogens

Rb

Cs

Fr Ra

Ba


La

Ac Rf


Db Sg Bh Hs Mt



H

Li Be

Na Mg


Ar

Ne

He

F

ClSPSiAl

B C N O

1A

2A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

3A 4A 5A 6A 7A

8ANoble Gases

Rb

Cs

Fr Ra

Ba


La

Ac Rf


Db Sg Bh Hs Mt



8/30/2010

16

Metals, nonmetals and metalloids1 IA

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 VIIIA

1 H

1.008

IIA

IIIA

IVA

VA

VIA

VIIA

2 He4.003

3 Li

6.941

4 Be 9.012

5 B

10.81

6 C

12.011

7 N

14.007

8 O

15.999

9 F

18.998

10 Ne20.179

11 Na 22.990

12 Mg 24.305

IIIB

IVB

VB

VIB

VIIB

[------VIIIB------]

IB

IIB

13 Al

26.982

14 Si

28.086

15 P

30.974

16 S

32.06

17 Cl

35.453

18 Ar

39.94819 K

39.098

20 Ca 40.08

21 Sc

44.956

22 Ti

47.90

23 V

50.942

24 Cr

51.996

25 Mn 54.938

26 Fe

55.847

27 Co 58.933

28 Ni 58.70

29 Cu 63.546

30 Zn 65.38

31 Ga 69.72

32 Ge 72.59

33 As 74.922

34 Se 78.96

35 Br

79.904

36 Kr 83.80

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 5437 Rb 85.468

38 Sr 87.62

39 Y

88.906

40 Zr 91.22

41 Nb 92.906

42 Mo 95.94

43 Tc (98)

44 Ru 101.07

45 Rh 102.91

46Pd 106.4

47 Ag 107.87

48 Cd 112.41

49 In

114.82

50 Sn 118.69

51 Sb 121.75

52Te

127.60

53I

126.90

54Xe

131.3055 Cs 132.91

56 Ba 137.33

57# La

138.91

72 Hf

178.49

73 Ta

180.95

74 W

183.85

75 Re 186.21

76 Os 190.2

77 Ir

192.22

78 Pt

195.09

79 Au 196.97

80 Hg 200.59

81 Tl

204.37

82 Pb 207.2

83 Bi

200.98

84 Po(209)

85 At (210)

86 Rn(222)

87 Fr (223)

88 Ra 226.03

89† Ac 227.03

104 Rf (261)

105 Db (262)

106 Sg (263)

107 Bh (262)

108 Hs (265)

109 Mt (268)

DLC 1o/97

# 58 Ce 140.12

59 Pr

140.91

60 Nd 144.24

61 Pm (145)

62 Sm 150.4

63 Eu 151.96

64 Gd 157.25

65 Tb

158.93

66 Dy 162.50

67 Ho 164.93

68 Er

167.26

69 Tm168.93

70 Yb173.04

71 Lu

174.97

† 90 Th

232.04

91 Pa

231.04

92 U

238.03

93 Np 237.05

94 Pu (244)

95 Am (243)

96 Cm (247)

97 Bk (247)

98 Cf (251)

99 Es (252)

100 Fm (257)

101 Md(258)

102 No(259)

103 Lr (260)

Nonmetals

Metals

Metalloids

Metals

• Left side of the periodic table– except H

• Properties:• Properties:– lustrous (shiny)

– good thermal and electrical conductors

– malleable

– solids at RT • except Hg = liquid

Non-Metals

• Right side of table– plus H

• Properties:• Properties:– Dull appearance

– Brittle when solids

– Do not conduct heat or electricity well

– Primarily solids or gases at RT• Bromine = liquid

8/30/2010

17

Metalloids

• Stair step between metals and non-metals

• Properties in between metals and non-metalsProperties in between metals and non metals– Si: brittle but semi-conductor

H

Li Be

Na Mg


Ar

Ne

He

F

ClSPSiAl

B C N O

1A

2A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

3A 4A 5A 6A 7A

8AMain Group or Representative

Elements

Rb

Cs

Fr Ra

Ba


La

Ac Rf


Db Sg Bh Hs Mt



H

Li Be

Na Mg


Ar

Ne

He

F

ClSPSiAl

B C N O

1A

2A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

3A 4A 5A 6A 7A

8ATransition Metals

Rb

Cs

Fr Ra

Ba


La

Ac Rf


Db Sg Bh Hs Mt



8/30/2010

18

H

Li Be

Na Mg


Ar

Ne

He

F

ClSPSiAl

B C N O

1A

2A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

3A 4A 5A 6A 7A

8ALanthanide Series

Rb

Cs

Fr Ra

Ba


La

Ac Rf


Db Sg Bh Hs Mt



H

Li Be

Na Mg


Ar

Ne

He

F

ClSPSiAl

B C N O

1A

2A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

3A 4A 5A 6A 7A

8A

Actinide Series

Rb

Cs

Fr Ra

Ba


La

Ac Rf


Db Sg Bh Hs Mt



The Periodic Table

Terminology of Periodic Table

Periods: Horizontal rows

Groups: Vertical columns

Main group elements: 1A - 8AGroup 1A: Alkali metal family

fGroup 2A: Alkaline earth metal familyGroup 7A: Halogen FamilyGroup 8A: Noble gas family

Transition metals or elements: 1B - 8B

Lanthanides: elements 58 – 71

Actinides: elements 90 – 103

Metals, nonmetals and metalloids

8/30/2010

19

We know where the protons and neutrons are located in an atom. But how are electrons really arranged around the nucleus?

Laws of mass1. Law of mass conservation: the total mass of substances does

not change during a chemical reaction.

“Matter cannot be created or destroyed”

Laws of mass2. Law of definitive composition: no matter what its source, a

particular compound is composed of the same elements in the same parts (fractions) by mass.

8/30/2010

20

Calculating the mass of an element in a compound

Laws of massLaw of multiple proportions: 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 ratio of small whole number.

Example: Formation of CO and CO2Example: Formation of CO and CO2

Inside the Atom

Review:

Three elementary particles: proton, electron and neutron

Protons contribute all the positive charge

Electrons contribute all the negative charge

Neutral atoms have net charge of zero, thus an equal number of protons g , q pand electrons

Protons and neutrons contribute nearly all the mass

Protons and neutrons are tightly bound together in the nucleus

Electrons surround the nucleus as a large “cloud” of negative charge

density

8/30/2010

21

The atomic notation of Silver is

109

Ag47

• Draw the diagram showing the arrangement of protons, neutrons d l t i il t and electrons in a silver atom.

• Draw the diagram showing the result of alpha-particle scattering experiment using silver foil.

Mole Concept

MoleOne mole is the amount of a substance that contains as many elementary entities (atoms, molecules, or other particles) as there are in exactly 12 g of carbon-12 isotope.

1 mole contains Avogadro's number of elementary entities.

Avogadro’s number: 6 02214155 x 1023 particles Avogadro s number: 6.02214155 x 10 particles

Molar massThe mass in grams of one mole of any element (6.022 x 1023 atoms of that element).

Units: grams per mole (g/mol).

An element’s molar mass is the amount in grams numerically equal to its atomic weight.


Determine the number of gallium (Ga) atoms present in 52.0 g of gallium.

8/30/2010

22


Symbol 65Cu 86Kr _______ ______

# of protons _____ _____ 78 ______

# of neutrons _____ ______ 117 46

# of electrons ______ ______ ____ 36

Name of the Element _____________ ______ ________

Symbol 65Cu 86Kr 195Pt 82Kr

# of protons 29 36 78 36

# of neutrons 36 50 117 46


# of electrons 29 36 78 36

Name of the copper Krypton Platinum Krypton

Element

The atomic notation of Silver is

109

Ag47

• Draw the diagram showing the arrangement of protons, neutrons d l t i il t and electrons in a silver atom.

• Draw the diagram showing the result of alpha-particle scattering experiment using silver foil.

8/30/2010

23

Three Kinds of Radiation

Alpha (α), beta (β), and gamma (γ)

Radiation Electric chargeα +2β -1γ 0

Documents

The Components of Matter · 2010-08-30 · Atomic Weight ¾For elements with more than one isotope, the atomic weight reported in the periodic table represents a weighted average