Copyright © Houghton Mifflin Company. All rights reserved.3–13–1 3.1 Internal Structure of an...

Copyright © Houghton Mifflin Company. All rights reserved. 3–1

3.1 Internal Structure of an Atom

Atoms were thought to be indivisible

In about 1900, it was learned that all atoms release negatively charged particles (electrons).

If there are negative particles, there must be positive particles (protons).


3.1 Internal Structure of an Atom

To make mass relationships work, there had to be neutral particles with about the same mass as protons (neutrons).


Charge and Mass Characteristics of Electrons, Protons, and Neutrons

Particle Mass(amu) Charge

electron 0.00054858 –1

proton 1.0073 +1

neutron 1.0087 0


Figure 3.1 The protons and neutrons of an atom are found in the central nuclear region, or nucleus, and the electrons are found in an electron cloud outside

the nucleus.


3.2 Atomic Number andMass Number

# of Protons = Z = Atomic Number# of Protons identifies the element

# Above element symbol on Periodic Table

# of Electrons = Z for neutral atom

“Protons give an element its identity, electrons give it its personality”

Darryl Ebbing to Bill Bryson


3.2 Atomic Number andMass Number

Mass # = # of Protons + # of Neutrons

# of Neutrons = Mass # - # of Protons


3.3 Isotopes and Atomic Masses

It is possible for atoms of the same element to have different numbers of neutrons.

These variants on an element are called isotopes.



Symbols for isotopes of an element:

1 2 3 12 13 14

H H H C C C 1 1 1 6 6 6

Protium Carbon-12

Deuterium Carbon-13

Tritium* Carbon-14*



The atomic mass of an element is a weighted average of the masses of the isotopes, on a relative scale.

Carbon-12 is defined to have a mass of exactly 12 atomic mass units (amu).



Atomic Mass of Chlorine:

75.53% of chlorine atoms are Chlorine 35, atomic mass = 34.97 amu

24.47% of chlorine atoms are Chlorine 37, atomic mass = 36.97 amu



Atomic Masses are given below the element’s symbol on the Periodic Table

7

NNitrogen14.0067


Chemistry at a Glance:Atomic Structure


3.4 The Periodic Law and the Periodic Table


Dmitri Mendeleev


The modern Periodic Table. Elements with similar chemical properties fall in the same vertical column.

PERIODIC TABLE OF THE ELEMENTS1 17 18

1A 7A 8A

1 1 2

H H HeHydrogen 2 13 14 15 16 Hydrogen Helium

1.00794 2A 3A 4A 5A 6A 1.00794 4.00260

3 4 5 6 7 8 9 10

Li Be B C N O F NeLithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon

6.941 9.01218 10.81 12.011 14.0067 15.9994 18.998403 20.1797

11 12 13 14 15 16 17 18

Na Mg Al Si P S Cl ArSodium Magnesium 3 4 5 6 7 8 9 10 11 12 Aluminum Silicon Phosphorus Sulfur Chlorine Argon

22.98977 24.305 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 26.98154 28.0855 30.97376 32.066 35.453 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 KrPotassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton

39.0983 40.078 44.9559 47.88 50.9415 51.996 54.9380 55.847 58.9332 58.69 63.546 65.39 69.72 72.61 74.9216 78.96 79.904 83.80

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 XeRubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon

85.4678 87.62 88.9059 91.224 92.9064 95.94 (98) 101.07 102.9055 106.42 107.8682 112.41 114.82 118.710 121.757 127.60 126.9045 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 RnCesium Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon

132.9054 137.33 138.9055 178.49 180.9479 183.85 186.207 190.2 192.22 195.08 196.9665 200.59 204.383 207.2 208.9804 (209) (210) (222)

87 88 89 104 105 106 107 108 109 110 111 112 114 116 118

Fr Ra **Ac Rf Db Sg Bh Hs MtFrancium Radium Actinium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium

(223) 226.0254 227.0278 (261) (262) (266) (264) (269) (268) (271) (272) (277) (289) (289) (293)

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

*Lanthanide Series Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb LuCerium Praesodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium

140.12 140.9077 144.24 (145) 150.36 151.96 157.25 158.9254 162.50 164.9304 167.26 168.9342 173.04 174.967

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

**Actinide Series Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No LrThorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium

232.0381 231.0359 238.0289 237.048 (244) (243) (247) (247) (251) (252) (257) (258) (259) (262)


Figure 3.4 In this periodic table, elements 58 - 71 and 90 through 13 (in color) are shown in their proper positions.


3.5 Metals, Nonmetals, etc.

Group (family) of elements--vertical columnPeriod (row) of elements--horizontal rowGroup 1A metals:alkali metalsGroup 2A metals: alkaline earth metalsGroups 1A – 8A: representative elementsGroups 1B – 8B: transition metalsGroup 7A: halogensGroup 8A: noble gases


Properties of Metals, Metalloids, and Nonmetals.

Metals

Metalloids (Semimetals)

Nonmetals

Conductors of Electricity Semiconductors of

Electricity Insulators of Electricity

Conduct Heat Well Conduct Heat Poorly

Metallic Luster Metallic Luster No Metallic Luster

Solid at Room Temp Solid at Room Temp State Varies with Molar

Mass

Malleable and Ductile Brittle Brittle


3.6 Electron Arrangement Within Atoms

Shells: Regions of space that contain electrons with about the same energyNumbered 1, 2, 3, 4

Correspond to rows on Periodic Table

Subshells: Regions of space within an electron shell that contain electrons with exactly the same energys, p, d, and f subshells

Correspond to regions on Periodic Table


Figure 3.7 The number of subshells within a shell is equal to the shell number, as shown here for the first four shells. Each individual subshell is denoted with both a number (its shell) and a letter (the type of subshell it is in).


Figure 3.8 An s orbital has a spherical shape

A p orbital has two lobesA d orbital has four lobes

An f orbital has eight lobes.


Figure 3.9 A summary of the interrelationships among shells, subshells, and orbitals for the first four shells.


Figure 3.10 The order of filling of various electron subshells is shown on the right-hand side of this diagram. Above the 3p subshell, subshells of different shells "overlap".


Figure 3.11 The order for filling electron subshells with electrons follows the order given by the arrows in this diagram. Start with the arrow at the top of the diagram and work toward the bottom of the diagram, moving from the bottom of one arrow to the top o the next-lower arrow.


3.7, 3.8 Electron Configurations And the Periodic Table

Elements within a family (group) have the same properties because their electron configurations are similar.

Elements in a family have the same number of electrons in their outermost (valence) shells.


Figure 3.12 Electron configurations and the positions of elements in the periodic table.


3.10 Nuclear Chemistry

Stable Nuclei: Do not change readilya.k.a. stable isotopes

Radioactive Nuclei: Undergo radioactive decaya.k.a. radioisotopes

Are transformed into different elements as part of radioactive decay


3.10 Nuclear Chemistry


3.11 Half-Life Decay of 80.0 mg of Iodine-131, t1/2 = 8.0 days.


Properties of Some Radionuclides.

Isotope

Half-Life

Emission

Use

Hydrogen-3 12 Years beta Water content of body

Carbon-14 5600 Years beta Radiocarbon dating

Iron-59 45 Days beta Anemia, bone marros

Cobalt-60 5.3 Years beta, gamma Cancer Therapy

Iodine-123 13 Hours gamma Diagnosis of Thyroid Cancer

Iodine-131 8.1 Days beta, gamma Treatment of Thyroid Cancer


3.12 Types of Radioactivity

Table 3.4 Characteristics of the Three Most Common Types of Radiation Given

off by Radioactive Atoms.


3.13 Radioactive Decay Equations (XI-1)

Sum of A’s (mass numbers) and Z’s (atomic numbers) on each side of the equation must be equal.


Alpha () EmissionHelium Nucleus ( particle) is Ejected

A 4 A–4

X + Y Z 2 Z–2

204 4 200

Pb + Hg 82 2 80

4 4 2+

= He

2 2


Beta () EmissionElectron ( particle) is Ejected

0 1–

= e –1

1 0 1

n + p 0 –1 1

A 0 A

X + Y Z –1 Z+1

14 0 14

C + N 6 –1 7


Gamma () Emission

No change in nucleus

Rays usually accompany other emissions

Release of energy


Positron (1+) EmissionPositively charged electron is emitted

A cyclotron is used to produce F-181 0 1

p + n 1 1 0

A 0 A

X + Y Z 1 Z–1

18 0 18

F + O 9 1 8


3.14 Biological Effects of Radiation

Called “Ionizing Radiation”

Knocks electrons out of their proper places

Produces reactive species where they don’t belong

Effect is similar to burning but penetrates more deeply than heat


Figure 3.15 Alpha, beta, and gamma radiations differ in penetrating ability.


Dose Effects

REM = Roentgen Equivalent in Man

1 Roentgen 1.8 x 1012 Ion Pairs gram of tissue

Dose, in REM’s Effects

0 – 25 None

25 – 100 Reduction of Blood Cells, No Symptoms

100 – 200 Nausea, Fatigue, Reduction of Blood Cells

200 – 300 Recovery in a Few Months

300 – 600 Some Deaths

600 + Most Die


3.15 Nuclear Medicine

Diagnostic Use: Tracers – “Make Noise”

A radioisotope will do the same chemistry as a stable isotope, can be used to see if some-thing is behaving normally


Properties of Radionuclides for Diagnoses

Short half-life (just long enough to prepare and administer)

Stable, nontoxic “daughters”

-Emitter so radiation gets out ( and just burn)

Reactivity with diseased tissue “hot spot” or “cold spot”


3.15 Nuclear Medicine

Therapy: “Hurt Something”

The radioisotope should get to target organ or tumor and emit radiation that destroys


Properties of Radionuclides for Therapy

Short half-life (just long enough to prepare and administer)

Stable, nontoxic “daughters”

or -Emitter to burn in concentrated area ( isn’t localized enough)

Reactivity with diseased tissue “hot spot” not “cold spot”


Other Medically Important Radiation

X-raysSlightly lower energy than -rays

Produced by beaming -particles on metal

Heavy elements are opaque to x-rays although they are not radioactive

Iodine, Barium



MRI (Magnetic Resonance Imaging)Magnetic field and radio-frequency beam

Not ionizing, very low energy

Can see water in tissue; hydrogen is active nucleus



UltrasoundHigh frequency sound energy

Not ionizing, very low energy

Looks for echoes, sound bounces off hard or stiff surfaces

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