chapter 2

HSTMr.WatsonDr. S. M. Condren

Atoms, Molecules

& Ions

Chapter 2

HST

HSTMr.Watson

Quantum Corral

http://www.almaden.ibm.com/vis/stm/corral.html

HSTMr.Watson

Scanning Tunneling Microscope

HSTMr.Watson

HSTMr.Watsonht

tp:/

/mrs

ec.w

isc.

edu/

http://mrsec.wisc.edu/

Developed in collaboration with theInstitute for Chemical Education and the

Magnetic Microscopy CenterUniversity of Minnesota

http://www.physics.umn.edu/groups/mmc/

HSTMr.Watson

Pull Probe StripProbe

Sample

Pull Probe Strip

http://w

ww

.nsf.g

ov/m

ps/dm

r/mrse

c.htm

http://www.nsf.gov/mps/dmr/mrsec.htm

HSTMr.Watson

(a) (b)

North South

(c)

Which best represents the poles?

HSTMr.Watson

Atoms & MoleculesAtoms

can exist alone or enter into chemical combination

the smallest indivisible particle of an element

Molecules

a combination of atoms that has its own characteristic set of properties

HSTMr.Watson

Law of Constant Composition

A chemical compound always contains the same elements in the same proportions by mass.

HSTMr.Watson

Law of Multiple Proportions

the same elements can be combined to form different compounds by combining the elements in different proportions

HSTMr.Watson

Dalton’s Atomic Theory

Postulates

proposed in 1803

know at least 2 for first exam

HSTMr.Watson


Postulate 1

An element is composed of tiny particles called atoms.

All atoms of a given element show the same chemical properties.

HSTMr.Watson


Postulate 2Atoms of different elements have different properties.

HSTMr.Watson


Postulate 3

Compounds are formed when atoms of two or more elements combine.

In a given compound, the relative number of atoms of each kind are definite and constant.

HSTMr.Watson


Postulate 4

In an ordinary chemical reaction, no atom of any element disappears or is changed into an atom of another element.

Chemical reactions involve changing the way in which the atoms are joined together.

HSTMr.Watson

Radioactivity

HSTMr.Watson

Radioactivity

Alpha – helium-4 nucleus

Beta – high energy electron

Gamma – energy resulting from transitions from one nuclear energy level to another

HSTMr.Watson

Alpha Radiation

composed of 2 protons and 2 neutrons

thus, helium-4 nucleus

+2 charge

mass of 4 amu

creates element with atomic number 2 lower

Ra226 Rn222 + He4()

HSTMr.Watson

Beta Radiation

composed of a high energy electron which was ejected from the nucleus

“neutron” converted to “proton”

very little mass

-1 charge

creates element with atomic number 1 higher

U239 Np239 + -1

HSTMr.Watson

Gamma Radiation

nucleus has energy levels

energy released from nucleus as the nucleus changes from higher to lower energy levels

no mass

no charge

Ni60* Ni60 +

HSTMr.Watson

Cathode Ray Tube

HSTMr.Watson

Thompson’s Charge/Mass Ratio

HSTMr.Watson

Millikin’s Oil Drop

HSTMr.Watson

Rutherford’s Gold Foil

HSTMr.Watson

Rutherford’s Model of the Atom

HSTMr.Watson

Rutherford’s Model of the Atom

atom is composed mainly of vacant space

all the positive charge and most of the mass is in a small area called the nucleus

electrons are in the electron cloud surrounding the nucleus

HSTMr.Watson

Structure of the Atom Composed of:

protons

neutrons

electrons

HSTMr.Watson

Structure of the Atom

Composed of:

protons

neutrons

electrons

protons– found in nucleus– relative charge of +1– relative mass of 1.0073 amu

HSTMr.Watson


Composed of:

protons

neutrons

electronsneutrons

– found in nucleus– neutral charge– relative mass of 1.0087 amu

HSTMr.Watson


Composed of:

protons

neutrons

electrons

electrons– found in electron cloud– relative charge of -1– relative mass of 0.00055 amu

HSTMr.Watson

Size of Nucleus

If the nucleus were1” in diameter,

the atom would be 1.5 miles in diameter.

HSTMr.Watson

Ions

charged single atom

charged cluster of atoms

HSTMr.Watson

Ions

cations– positive ions

anions– negative ions

ionic compounds– combination of cations and anions– zero net charge

HSTMr.Watson

Atomic number, Z

the number of protons in the nucleus

the number of electrons in a neutral atom

the integer on the periodic table for each element

HSTMr.Watson

Isotopes

atoms of the same element which differ in the number of neutrons in the nucleus

designated by mass number

HSTMr.Watson

Mass Number, A

integer representing the approximate mass of an atom

equal to the sum of the number of protons and neutrons in the nucleus

HSTMr.Watson

Masses of Atoms

Carbon-12 Scale

HSTMr.Watson

Isotopes of Hydrogen H-1, 1H, protium

1 proton and no neutrons in nucleus

only isotope of any element containing no neutrons in the nucleus

most common isotope of hydrogen

HSTMr.Watson

Isotopes of Hydrogen H-2 or D, 2H, deuterium

1 proton and 1 neutron in nucleus

HSTMr.Watson

Isotopes of Hydrogen H-3 or T, 3H, tritium

1 proton and 2 neutrons in nucleus

HSTMr.Watson

Isotopes of Oxygen

O-16

8 protons, 8 neutrons, & 8 electrons

O-17


O-18


HSTMr.Watson

The radioactive isotope 14C has how many neutrons?

6, 8, other

HSTMr.Watson

The identity of an element is determined by the number of which particle?

protons, neutrons, electrons

HSTMr.Watson

Mass Spectrometer

HSTMr.Watson

Mass Spectra of Neon

HSTMr.Watson

Measurement of Atomic Masses

Mass Spectrometer

a simulation is available at

http://www.colby.edu/chemistry/

OChem/DEMOS/MassSpec.html

HSTMr.Watson

Atomic Masses andIsotopic Abundances

natural atomic masses =

sum[(atomic mass of isotope)

*(fractional isotopic abundance)]

HSTMr.Watson

Example: Chlorine has two isotopes, Cl-35 and Cl-37, which have masses of 34.96885 and 36.96590 amu, respectively. The natural atomic mass of chlorine is 35.453 amu. What are the percent abundances of the two isotopes?

let x = fraction Cl-35 y = fraction Cl-37

x + y = 1 y = 1 - x

(AW Cl-35)(fraction Cl-35) + (AW Cl-37)(fraction Cl-37) = 35.453

Thus:34.96885*x + 36.96590*y = 35.453

HSTMr.Watson


let x = fraction Cl-35

y = fraction Cl-37

x + y = 1 <=> y = 1 - x

HSTMr.Watson



y = fraction Cl-37

x + y = 1 <=> y = 1 - x


HSTMr.Watson



y = fraction Cl-37

x + y = 1 <=> y = 1 - x


34.96885*x + 36.96590*y = 35.453

34.96885*x + 36.96590*(1-x) = 35.453

HSTMr.Watson

Example: Chlorine has two isotopes, Cl-35 and Cl-37, which have masses of 34.96885 and 36.96590 amu, respectively. The natural atomic mass of chlorine is 35.453 amu. What are the percent abundances of the two isotopes?let x = fraction Cl-35 y = fraction Cl-37x + y = 1 <=> y = 1 - x


34.96885*x + 36.96590*y = 35.45334.96885*x + 36.96590*(1-x) = 35.453(34.96885 - 36.96590)x + 36.96590 =

35.453

HSTMr.Watson

Example: Chlorine has two isotopes, Cl-35 and Cl-37, which have masses of 34.96885 and 36.96590 amu, respectively. The natural atomic mass of chlorine is 35.453 amu. What are the percent abundances of the two isotopes?let x = fraction Cl-35

y = fraction Cl-37

x + y = 1 <=> y = 1 - x


34.96885*x + 36.96590*y = 35.453

34.96885*x + 36.96590*(1-x) = 35.453

(34.96885 - 36.96590)x + 36.96590 = 35.453

HSTMr.Watson



y = fraction Cl-37

x + y = 1 <=> y = 1 - x


34.96885*x + 36.96590*y = 35.453

34.96885*x + 36.96590*(1-x) = 35.453

(34.96885 - 36.96590)x + 36.96590 = 35.453

(34.96885 - 36.96590)x = (35.453 - 36.96590)

HSTMr.Watson


y = fraction Cl-37

x + y = 1 <=> y = 1 - x


34.96885*x + 36.96590*y = 35.453

34.96885*x + 36.96590*(1-x) = 35.453

(34.96885 - 36.96590)x + 36.96590 = 35.453

(34.96885 - 36.96590)x = (35.453 - 36.96590)

- 1.99705x = - 1.5129

HSTMr.Watson


y = fraction Cl-37

x + y = 1 <=> y = 1 - x


34.96885*x + 36.96590*y = 35.453

34.96885*x + 36.96590*(1-x) = 35.453

(34.96885 - 36.96590)x + 36.96590 = 35.453

(34.96885 - 36.96590)x = (35.453 - 36.96590)

- 1.99705x = - 1.5129

1.99705x = 1.5129

HSTMr.Watson


y = fraction Cl-37

x + y = 1 <=> y = 1 - x


34.96885*x + 36.96590*y = 35.453

34.96885*x + 36.96590*(1-x) = 35.453

(34.96885 - 36.96590)x + 36.96590 = 35.453

(34.96885 - 36.96590)x = (35.453 - 36.96590)

- 1.99705x = - 1.5129

1.99705x = 1.5129

x = 0.7553 <=> 75.53% Cl-35

HSTMr.Watson

Example: Chlorine has two isotopes, Cl-35 and Cl-37, which have masses of 34.96885 and 36.96590 amu, respectively. The natural atomic mass of chlorine is 35.453 amu. What are the percent abundances of the two isotopes?let x = fraction Cl-35 y = fraction Cl-37x + y = 1 <=> y = 1 - x(AW Cl-35)(fraction Cl-35) + (AW Cl-37)(fraction Cl-37) = 35.45334.96885*x + 36.96590*y = 35.45334.96885*x + 36.96590*(1-x) = 35.453(34.96885 - 36.96590)x + 36.96590 = 35.453(34.96885 - 36.96590)x = (35.453 - 36.96590)- 1.99705x = - 1.5129

1.99705x = 1.5129 x = 0.7553 <=> 75.53% Cl-35

y = 1 - x

HSTMr.Watson


1.99705x = 1.5129 x = 0.7553 <=> 75.53% Cl-35

y = 1 - x = 1.0000 - 0.7553

HSTMr.Watson


1.99705x = 1.5129 x = 0.7553 <=> 75.53% Cl-35

y = 1 - x = 1.0000 - 0.7553 = 0.2447

HSTMr.Watson


let x = fraction Cl-35 y = fraction Cl-37x + y = 1 <=> y = 1 - x(AW Cl-35)(fraction Cl-35) + (AW Cl-37)(fraction Cl-37) = 35.45334.96885*x + 36.96590*y = 35.45334.96885*x + 36.96590*(1-x) = 35.453(34.96885 - 36.96590)x + 36.96590 = 35.453(34.96885 - 36.96590)x = (35.453 - 36.96590)- 1.99705x = - 1.5129

1.99705x = 1.5129 x = 0.7553 <=> 75.53% Cl-35

y = 1 - x = 1.0000 - 0.7553 = 0.2447 24.47% Cl-37

HSTMr.Watson

Development of Periodic Table

Newlands - English

1864 - Law of Octaves - every 8th element has similar

properties

HSTMr.Watson

Development of Periodic Table

Dmitri Mendeleev - Russian

1869 - Periodic Law - allowed him to predict properties of

unknown elements

HSTMr.Watson

Mendeleev’s Periodic Table

the elements are arranged according to increasing atomic weights

HSTMr.Watson

Missing elements: 44, 68, 72, & 100 amu

Mendeleev’s Periodic Table

HSTMr.Watson

Properties of Ekasilicon

HSTMr.Watson

Modern Periodic TableMoseley, Henry Gwyn Jeffreys

1887–1915, English physicist.

Studied the relations among bright-line spectra of different elements.

Derived the ATOMIC NUMBERS from the frequencies of vibration of X-rays emitted by each element.

Moseley concluded that the atomic number is equal to the charge on the nucleus.

This work explained discrepancies in Mendeleev’s Periodic Law.

HSTMr.Watson

Modern Periodic Table

the elements are arranged according to increasing atomic numbers

HSTMr.Watson

I A II A III B IV B V B VI B VII B VIII B I B II B III A IV A V A VI A VII A VIII A1 1 2

1 H H He1.008 1.008 4.0026

3 4 5 6 7 8 9 10

2 Li Be B C N O F Ne6.939 9.0122 10.811 12.011 14.007 15.999 18.998 20.183

11 12 13 14 15 16 17 18

3 Na Mg Al Si P S Cl Ar22.99 24.312 26.982 28.086 30.974 32.064 35.453 39.948

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

4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr39.102 40.08 44.956 47.89 50.942 51.996 54.938 55.847 58.932 58.71 63.54 65.37 69.72 72.59 74.922 78.96 79.909 83.8

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

5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe85.468 87.62 88.906 91.224 92.906 95.94 * 98 101.07 102.91 106.42 107.9 112.41 114.82 118.71 121.75 127.61 126.9 131.29

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

6 Cs Ba **La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn132.91 137.33 138.91 178.49 180.95 183.85 186.21 190.2 192.22 195.08 196.97 200.29 204.38 207.2 208.98 * 209 * 210 * 222

87 88 89 104 105 106 107 108 109 110 111 112 113 114 115 116 118

7 Fr Ra ***Ac Rf Ha Sg Ns Hs Mt Uun Uuu Uub Uut Uuq Uup Uuh Uuo* 223 226.03 227.03 * 261 * 262 * 263 * 262 * 265 * 268 * 269 * 272 * 277 *284 *285 *288 *292 *294

Based on symbols used by ACS S.M.Condren 2007

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

* Designates that **Lanthanum Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Luall isotopes are Series 140.12 140.91 144.24 * 145 150.36 151.96 157.25 158.93 162.51 164.93 167.26 168.93 173.04 174.97

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

*** Actinium Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Series 232.04 231.04 238.03 237.05 * 244 * 243 * 247 * 247 * 251 * 252 * 257 * 258 * 259 * 260

Periodic Table of theElements

Periodic Table of the ElementsPeriodic Table of the Elements

HSTMr.Watson

Organization of Periodic Table

period - horizontal row

group - vertical column

HSTMr.Watson

Family Names

Group IA alkali metalsGroup IIA alkaline earth metalsGroup VIIA halogensGroup VIIIAnoble gasestransition metalsinner transition metalslanthanum series rare earthsactinium series trans-uranium series

HSTMr.Watson

Types of Elements

metals

nonmetals

metalloids - semimetals

HSTMr.Watson

Elements, Compounds, and Formulas

Elements

can exist as single atoms or molecules

Compounds

combination of two or more elements

molecular formulas for molecular compounds

empirical formulas for ionic compounds

HSTMr.Watson

Organic CompoundsOrganic Chemistry

branch of chemistry in which carbon compounds and their reactions are studied.

the chemistry of carbon-hydrogen compounds

HSTMr.Watson

Inorganic Compounds Inorganic Chemistry

field of chemistry in which are studied the chemical reactions and properties of all the chemical elements and their compounds, with the exception of the hydrocarbons (compounds composed of carbon and hydrogen) and their derivatives.

HSTMr.Watson

Molecular and Structural Formulas

HSTMr.Watson

Bulk Substances

mainly ionic compounds– empirical formulas– structural formulas

HSTMr.Watson

Models of Sodium Chloride

NaCl “table salt”

HSTMr.Watson

How many atoms are in the formula Al2(SO4)3?

3, 5, 17

HSTMr.Watson

Naming Binary Molecular Compounds

For compounds composed of two non-metallic elements, the more metallic element is listed first.

To designate the multiplicity of an element, Greek prefixes are used:

mono => 1; di => 2; tri => 3; tetra => 4; penta => 5; hexa => 6; hepta => 7; octa => 8

HSTMr.Watson

Common CompoundsH2O

water

NH3

ammonia

N2O

nitrous oxide

CO

carbon monoxide

CS2

carbon disulfide

SO3

sulfur trioxide

CCl4carbon tetrachloride

PCl5phosphorus

pentachloride

SF6

sulfur hexafluoride

HSTMr.Watson

Alkanes - CnH2n+2

methane - CH4

ethane - C2H6

propane - C3H8

butanes - C4H10

pentanes - C5H12

hexanes - C6H14

heptanes - C7H16

octanes - C8H18

nonanes - C9H20

decanes - C10H22

HSTMr.Watson

Burning of Propane Gas

HSTMr.Watson

Butanes

HSTMr.Watson

Ionic Bonding

Characteristics of compounds with ionic bonding:

non-volatile, thus high melting points

solids do not conduct electricity, but melts (liquid state) do

many, but not all, are water soluble

HSTMr.Watson

Ion Formation

HSTMr.Watson

ValanceCharge on Ions

compounds have electrical neutrality

metals form positive monatomic ions

non-metals form negative monatomic ions

HSTMr.Watson

Valence of Metal Ions

Monatomic Ions

Group IA => +1

Group IIA => +2

Maximum positive valence

equals

Group A #

HSTMr.Watson

Valence of Non-Metal Ions

Monatomic Ions

Group VIA => -2

Group VIIA => -1

Maximum negative valence

equals

(8 - Group A #)

HSTMr.Watson

Charges of Some Important Ions

HSTMr.Watson

Polyatomic Ions

more than one atom joined together

have negative charge except for NH4+ and

its relatives

negative charges range from -1 to -4

HSTMr.Watson

Polyatomic Ionsammonium NH4

+

perchlorateClO41-

cyanide CN1-

hydroxide OH1-

nitrate NO31-

sulfate SO42-

carbonate CO32-

phosphate PO43-

HSTMr.Watson

Names of Ionic Compounds

1. Name the metal first.

If the metal has more than one oxidation state, the oxidation state is specified by Roman numerals in parentheses.

2. Then name the non-metal,

changing the ending of the non-metal to

-ide.

HSTMr.Watson

NomenclatureNaCl

sodium chloride

Fe2O3

iron(III) oxide

N2O4

dinitrogen tetroxide

KI

potassium iodide

Mg3N2

magnesium nitride

SO3

sulfur trioxide

HSTMr.Watson

NomenclatureNH4NO3

ammonium nitrate

KClO4

potassium perchlorate

CaCO3

calcium carbonate

NaOH

sodium hydroxide

HSTMr.Watson

Nomenclature Drill

Available for PCs:–

http://science.widener.edu/svb/pset/nomen_b.html

– in the Chemistry Resource Center– , Links

http://en.wikipedia.org/wiki/IUPAC_nomenclature_of_organic_chemistry

HSTMr.Watson

How many moles of ions are there per mole of Al2(SO4)3?

2, 3, 5

HSTMr.Watson

Chemical Equation

reactants

products

coefficients

reactants -----> products

HSTMr.Watson

Writing and BalancingChemical Equations

Write a word equation.

Convert word equation into formula equation.

Balance the formula equation by the use of prefixes (coefficients) to balance the number of each type of atom on the reactant and product sides of the equation.

HSTMr.Watson

Example

Hydrogen gas reacts with oxygen gas to produce water.

Step 1.

hydrogen + oxygen -----> water

Step 2.

H2 + O2 -----> H2O

Step 3.

2 H2 + O2 -----> 2 H2O

HSTMr.Watson

Example

Iron(III) oxide reacts with carbon monoxide to produce the iron oxide (Fe3O4) and carbon dioxide.

iron(III) oxide + carbon monoxide -----> Fe3O4 + carbon dioxide

Fe2O3 + CO -----> Fe3O4 + CO2

3 Fe2O3 + CO -----> 2 Fe3O4 + CO2

chapter 2

Documents