Announcements - Sailor Research Group HOMEsailorgroup.ucsd.edu/Chem6A_sailor/Chapter2.pdf · 2011-09-29 · Announcements Chem 6A Sept 27, 2011 ... Electron e 1 9.1x-1028 Proton p

Chem 6A Michael J. Sailor, UC San Diego

AnnouncementsChem 6A Sept 27, 2011

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1


Chapter 2: Matter

2

Chem 6A Michael J. Sailor, UC San Diego 3

Properties of sub-atomic particlesName Symbol Charge* Mass, g

Electron e-‐ -‐1 9.1 x 10-‐28

Proton p +1 1.673 x 10-‐24

Neutron n 0 1.675 x 10-‐24

*units are fundamental unit of charge, = 1.602 x 10-19 coulombs


The Periodic Table of the Elements

4

1 18

1 2

H 2 13 14 15 16 17 He1.0079 4.0026

3 4 5 6 7 8 9 10

Li Be B C N O F Ne6.941 9.01218 10.811 12.011 14.0067 15.9994 18.9984 20.1797

11 12 13 14 15 16 17 18

Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S Cl Ar22.9898 24.305 26.9815 28.0855 30.9738 32.066 35.4527 39.948

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr39.0983 40.078 44.9559 47.88 50.9415 51.9961 54.9381 55.847 58.9332 58.69 63.546 65.39 69.723 72.61 74.9216 78.96 79.904 83.8

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe85.4578 87.62 88.9059 91.224 92.9064 95.94 98.9063 101.07 102.906 106.42 107.868 112.411 114.82 118.71 121.75 127.6 126.905 131.29

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn132.905 137.327 138.906 178.49 180.948 183.85 186.207 190.2 192.22 195.08 196.967 200.59 204.383 207.2 208.98 208.982 209.987 222.018

87 88 89 104 105 106 107 108 109

Fr Ra Ac Unq Unp Unh Uns Uno Une223.02 226.025 227.028 - - - - - -

58 59 60 61 62 63 64 65 66 67 68 69 70 71

Lanthanides Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu140.12 140.91 144.24 146.92 150.35 151.96 157.25 158.92 162.5 164.93 167.26 168.93 173.04 174.97

90 91 92 93 94 95 96 97 98 99 100 101 102 103

Actinides Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr232.038 231.04 238.03 237.05 239.05 241.06 247.07 249.08 251.08 254.09 257.1 258.1 255 262.1


3 key experiments leading to the modern view of the atom

Person Experiment What it determined

J.J. Thomson1897

Effect of a charged plates on a cathode ray tube

mass/charge ratio of an electron, me/ze

Robert Millikan1909

Oil-drop experiment: suspending a charged drop of oil between two charged plates

charge on the electron, ze

Ernest Rutherford1910

Scattering of alpha-rays from metal foils

Atom consists of a very small, very dense nucleus


Electrons

Cathode Ray (or Crookes) Tube measures the charge/mass ratio of the electron

Effect of magnetic and electric fields on the deflection of the beam can determine the mass to charge ratio, me/ze


The CRT television display is a descendant of the Crookes tube


Determination of the charge of the electron


Problem: charge on the electron

Determine the fundamental charge on the electron, in esu

0

1 10-9

2 10-9

3 10-9

4 10-9

5 10-9

1 2 3 4 5 6 7 8 9 10

charge, esu

ch

arg

e,

esu

measurement

Charge on oil drop(esu)

9.60 x 10-10

1.92 x 10-9

2.40 x 10-9

2.88 x 10-9

4.80 x 10-9


Solution: charge on the electron

(1) Sort by charge:

0

1 10-9

2 10-9

3 10-9

4 10-9

5 10-9

9 1 6 2 3 4 10 8 5 7

charge, esu

ch

arg

e,

esu

measurement


0

1

2

3

4

5

6

9 1 6 2 3 4 10 8 5 7

Divide by LCD

ch

arg

e,

esu

/9.6

x1

0-1

0

measurement

11


(1) Sort by charge:(2) Divide by

smallest charge:


0

1

2

3

4

5

6

7

8

9

10

11

12

9 1 6 2 3 4 10 8 5 7

multiply by 2

ch

arg

e,

esu

/9.6

x1

0-1

0

measurement

12


(1) Sort by charge:(2) Divide by

smallest charge:(3) Multiply by 2:


Solution: charge on the electronEsu Divide by 9.6 x 10-10 Multiply by 2

9.60x10-10 1 21.92x10-9 2 42.40x10-9 2.5 52.88x10-9 3 6

4.80x10-9 5 10

So the fundamental charge on the electron is:(9.6 x 10-10)/2 = 4.8 x 10-10 esu


Discovery of the nucleus


3 key experiments leading to the modern view of the atom

Person Experiment What it determined

J.J. Thomson1897

Effect of a charged plates on a cathode ray tube

mass/charge ratio of an electron, me/ze

Robert Millikan1909

Oil-drop experiment: suspending a charged drop of oil between two charged plates

charge on the electron, ze

Ernest Rutherford1910

Scattering of alpha-rays from metal foils

Atom consists of a very small, very dense nucleus


A mass spectrometer measures masses* of ions

*more correctly, the mass to charge ratio, m/z


Definition of atom masses is based on 12C

• A carbon-12 atom is defined as our mass standard• it weighs exactly 12 atomic mass units (amu).

• 1 amu = 1.66054 x 10-24g

…so why does the periodic table list C as 12.011?


Mass ratios, isotopes, and %abundance

12C13C

12C, 13C

More 12C: bigger spot

Less13C: smaller spot

mass

inte

nsity

12 13 1411


Isotopes: mass ratios and percent abundance

Element Mass (position on detector)

Abundance (intensity on detector)12C 12.00 98.89

13C 13.003355 1.11Mass ratio: 1.0836129

Mass ratio:

€

13C12C

=13.003355

12=1.0836129


Problem: percent abundance of isotopes

A student uses a mass spectrometer to determine the masses and percent abundances of all the naturally occurring isotopes of chlorine, the values of which are presented below. Calculate the average mass of chlorine, in amu.

Isotope % abundant Atomic Mass, amu 35Cl 75.77 % 34.97 37Cl 24.23 % 36.97


Solution: percent abundance of the isotopes

This is just a weighted average:

Mass = (0.7577 x 34.97) + (0.2423 x 36.97) = 35.45 amu

The average of all naturally occurring isotopes is called the atomic mass (or atomic weight) of an element


Detection of peptides in human blood by mass spectrometry

mass spectrum of blood serum from human

inte

nsity

Villanueva, J. et al., Analytical Chemistry 2004, 76, 1560-1570

white = peptide present

blue = peptide not present


Application of mass spectrometry to detection of cancer

mass spectra of blood serum obtained from patients with and without brain tumors (Villanueva, J. et al., Analytical Chemistry 2004, 76, 1560)


The Periodic Table of the Elements

24

1 18

1 2

H 2 13 14 15 16 17 He1.0079 4.0026

3 4 5 6 7 8 9 10

Li Be B C N O F Ne6.941 9.01218 10.811 12.011 14.0067 15.9994 18.9984 20.1797

11 12 13 14 15 16 17 18

Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S Cl Ar22.9898 24.305 26.9815 28.0855 30.9738 32.066 35.4527 39.948

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr39.0983 40.078 44.9559 47.88 50.9415 51.9961 54.9381 55.847 58.9332 58.69 63.546 65.39 69.723 72.61 74.9216 78.96 79.904 83.8

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe85.4578 87.62 88.9059 91.224 92.9064 95.94 98.9063 101.07 102.906 106.42 107.868 112.411 114.82 118.71 121.75 127.6 126.905 131.29

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn132.905 137.327 138.906 178.49 180.948 183.85 186.207 190.2 192.22 195.08 196.967 200.59 204.383 207.2 208.98 208.982 209.987 222.018

87 88 89 104 105 106 107 108 109

Fr Ra Ac Unq Unp Unh Uns Uno Une223.02 226.025 227.028 - - - - - -

58 59 60 61 62 63 64 65 66 67 68 69 70 71

Lanthanides Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu140.12 140.91 144.24 146.92 150.35 151.96 157.25 158.92 162.5 164.93 167.26 168.93 173.04 174.97

90 91 92 93 94 95 96 97 98 99 100 101 102 103

Actinides Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr232.038 231.04 238.03 237.05 239.05 241.06 247.07 249.08 251.08 254.09 257.1 258.1 255 262.1


Bonding in Compounds

covalent ionic

Covalent bond = neutral atoms held together by sharing a pair of electrons

Ionic bond = charged atoms (ions) held together by electrostatic forces

€

E =z1z2q

2

4πεor1−2

Coulomb’s law:charge

distance

Na+

Cl-H

H

O ClCl

water moleculechlorine molecule


The rock salt lattice

Ionic solids are held together by ionic bonds


Energy of an ionic bondIonic bond = charged atoms

(ions) held together by electrostatic forces

€

E =z1z2q

2

4πεor1−2

Coulomb’s law:charge

distanceNa+Cl-

Energy of attraction between 1 Na+ and 1 Cl- is

€

E =z1z2q

2

4πε or1−2=

(+1)(−1)(1.602 ×10−19)2

(4)(3.14)(8.85 ×10−12)(2.81×10−10)= 8.2 ×10−19J

0.281 nm


Lattice enthalpies and ionic radius

650

700

750

800

850

900

950

3 3.2 3.4 3.6 3.8 4 4.2 4.4

Lattice Enthalpy vs 1/(Ionic radii)

Latt

ice

enth

alpy

, kJ/

mol

1/(Na-X) distance, Å- 1

NaF

NaCl

NaBr

NaI

Ion Radius (pm)F- 13.3

Cl- 18.1

Br- 19.6

I- 22.0

Lattice enthalpy = energy that holds the crystal together

The closer the ions, the stronger the lattice


Silberberg, pg. 53: Common Monatomic Ions


Covalent bonds

covalent

Covalent bond = neutral atoms held together by sharing a pair of electrons

•An assembly of atoms held together by covalent bonds is a molecule

•If it has a net charge, it is called a molecular ion

ClCl

water moleculechlorine molecule

H

H

O


Problem: Naming polyatomic ions (Table 2.5)

Write the names of the following ions:Write the names of the following ions:Write the names of the following ions:1. CH3CO2

-

2. Cr2O72-

3. ClO3-

4. MnO4-

acetatedichromatechloratepermanganate

Memorize all the ions, names, formulas and charges in Table 2.3, 2.4, and 2.5


Problem:

What is the MOLAR MASS of Aspirin (acetylsalicylic acid):

(C9H8O4)

O

O

CH3

O OH

H

H

H

H


Solution:

MOLAR MASS of Aspirin (acetylsalicylic acid):

O

O

CH3

O OH

H

H

H

H

(C9H8O4) = 9(12.011) + 8(1.0079) + 4(15.9994) = 180.16 g/mol


Problem:

What is the percent by mass of carbon in Aspirin?

(C9H8O4)

O

O

CH3

O OH

H

H

H

H


Solution: elemental composition of aspirin

Atom Number Molecular weight (g/mol)

Mass %by mass

C 9 12.011 108.099 60.00

H 8 1.0079 8.0632 4.48

O 4 15.9994 63.9976 35.52

TOTAL: 100.00


Extras

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Announcements - Sailor Research Group HOMEsailorgroup.ucsd.edu/Chem6A_sailor/Chapter2.pdf · 2011-09-29 · Announcements Chem 6A Sept 27, 2011 ... Electron e 1 9.1x-1028 Proton p