Atoms,Molecules,

and Ions

Unit 2:Elements and Compounds:

Atoms, Molecules & Ions

CHM 1045: General Chemistry and Qualitative Analysis

Dr. Jorge L. AlonsoMiami-Dade College –

Kendall CampusMiami, FL

Textbook References: •Modules #2 & 5

Atoms,Molecules,

and Ions

The Early Development of the

Atomic Theory

Atoms,Molecules,

and Ions

Leucippus of Miletus & Democritus of Abdera (Gk. 5th Cent BC)

• More philosophical than experimental in origin. • Matter is made up of very small individual atomos -

objects that are indivisible. • Everything is made up of these atoms, which move

around in a void (a vacuum). • The different physical properties -- color, taste, and

so on -- of materials come about because atoms in them are different shapes and/or arrangements and orientations with respect to each other.

Ancient Atomic Theory

Atoms,Molecules,

and Ions

Medieval Alchemy (al-khimia ,الخيمياء)

Science as an early form of investigation, with

occult philosophical and spiritual traditions.Jabir ibn Hayyan

Merlin the Magician

Principal aim of Alchemist:

• the transmutation of common metals into gold or silver.

Cinnabar (red powder) Hg

Zn, Cu, Fe Au or Ag

• the creation of a "panacea," or the elixir of life, a remedy that supposedly would cure all diseases and prolong life indefinitely.

Atoms,Molecules,

and Ions

Chemistry in the Age of Enlightment

27 g 25 g + 2 g (s) (l) (g)

(1743 - 1794)

{HgOMovie}

Law of Conservation of Mass:

Atoms,Molecules,

and Ions

Expt. Water Hydrogen + Oxygen

#1 9.0 g 1.0 g 8.0 g

#2 18.0 g 2.0 g 16.0 g

#3 13.5 g 1.5 g 12.0 g

Expt. Hydrogen Peroxide

Hydrogen + Oxygen

#1 17.0 g 1.0 g 16.0 g

#2 34.0 g 2.0 g 32.0

#3 25.5 g 1.5 g 24.0 g

Law of Constant Composition (or Definite Proportions)

(1754–1826)

Compared masses of different elements within the same compound.

In Water Ratio H :O

1 : 8

In H-Peroxide Ratio H : O

1 :16

*

Atoms,Molecules,

and Ions

Dalton’s Law of Multiple Proportion

When two elements form two different compounds, the mass ratio of the elements in one compound is related to the mass ratio in the other compound by a small whole number.

C + O2 (high oxy.conc.) CO2

C + O2 (low oxy.conc.) CO

2.67 g 12.0g 0.32

Carbon massOxygen mass

1.33 g 12.0g 0.16

Carbon massOxygen mass

John Dalton (1766–1844).

2.00 g 1.33g 67.2

Atoms,Molecules,

and Ions

Dalton’s Atomic Theory (1801)

1. All matter is made up of small indivisible particles called atoms.

2. The properties of the atoms of one element differ form those of all other elements.

3. Atoms can neither be created nor destroyed.

4. All atoms of the same element are identical in mass, size, and physical properties.

5. Atoms combine in small whole number ratios to form compounds.

•All matter is made up of small indivisible particles called atoms.•The properties of the atoms of one element differ from those of all other elements.•Atoms can neither be created nor destroyed.•All atoms of the same element are identical in mass, size, and physical properties.•Atoms combine in small whole number ratios to form compounds.

*

Atoms,Molecules,

and Ions

{Electroscope Movie}

                              

The Electron

Electrically charged particles can be rubbed-out of many substances such as glass rods, hair, shoes, rubber tires and shoes.

Excess of electrons

Lack of electrons{Electroscope Movie*}

Van de Graaff Generator

Electric motor

Rubber band

Rubber band rubs metals inside

Atoms,Molecules,

and Ions

The Electron

Movie 1 Movie 2 Movie 3

• cathode ray tubes produce negatively charged particles (electrons) from chemicals in batteries.

• J. J. Thompson is credited with their

discovery (1897).

Batteries (chemicals)

Electron Rays

Atoms,Molecules,

and Ions

The Atom, circa 1900

• “Plum pudding” model, put forward by J. J. Thompson.

• Positive sphere of matter with negative electrons imbedded in it.

Atoms,Molecules,

and Ions

Discovery of the Nucleus

In 1909 Ernest Rutherford shot particles at a thin sheet of gold foil and observed the pattern of scatter of the particles.

*

He42

Atoms,Molecules,

and Ions

The Nuclear Atom

Since some particles were deflected at large angles, J. J. Thompson’s model could not be correct.

{*Rutherfords Experiment}

Atoms,Molecules,

and Ions

The Nuclear Atom According to Rutherford

• He postulated a very small, dense nucleus with the electrons around the outside of the atom.

• Most of the volume of the atom is empty space.

Difference of 105 = 100,000

Atoms,Molecules,

and Ions

Historical Development of Atomic Theory

{Bohr Planetary vs. Quantum Model}

Atoms,Molecules,

and Ions

Scanning Tunneling Microscopy (STM)

Atoms,Molecules,

and Ions

‘Seeing’ Atoms: Scanning Tunneling Microscope

Atoms,Molecules,

and Ions

‘Seeing’ Atoms: Scanning Tunneling Microscope

Atoms,Molecules,

and Ions

Subatomic Particles: Charge & Mass

• Protons and neutrons have essentially the same mass.• The mass of an electron is so small we ignore it.

• Protons were discovered by Rutherford in 1919.

• Neutrons were discovered by James Chadwick in 1932.

{ProtonDiscoveryMovie}

Atoms,Molecules,

and Ions

ElementsPure substances that cannot be broken down into more

elemental particles by ordinary chemical means.

IIIA IVA VA VIA VIIA

IA

IIB IVB VB VIB VIIB VIII IB IIB

VIIIA

IIAA. Atomic number

B. Mass number

C. Isotopes

D. Atomic mass or weigh

Atoms,Molecules,

and Ions

Elements & Atomic terminology

• Atomic number (Z) = #p

• Mass number (A) = (#p+) + (#no)

A = Z + N

• Isotopes

• Atomic mass or weigh (a.m.u. or grams)

Atoms of the same element (same at. #), having different number of neutrons.

The average mass of the isotopes of an element, considering their natural % abundance.

#p = #e- in a neutral atom Identifies the element

Atoms,Molecules,

and Ions

• Atoms of the same element with different masses (mass number)

Isotopes

• Isotopes have different numbers of neutrons.

Isotopes of Carbon: (isotope notation)

116C

126C

136C

146C

Mass number

Atomic number

99.985% 0.015% 0% Natural Abundance

0.000137% 99.999863% Natural Abundance

7.59% 92.41% Natural Abundance

Natural Abundance: negligible 98.89% 1.11% negligible

*

(atomic number =1)

(atomic number =2)

(atomic number =3)Atomic mass or weigh?

Atoms,Molecules,

and Ions

Isotopes of Hydrogen1H 2H 3H

Natural

Abundance 99.985% 0.015% negligible

unstable, radioactive

Atoms,Molecules,

and Ions

Isotopes of Carbon

Natural

Abundance 98.89% 1.11% negligible

12C 13C 14C

Atoms,Molecules,

and Ions

Table of Isotopes (partial)

Atoms,Molecules,

and Ions

Determination of Atomic MassMass spectrometer: can separate isotopes of an element based on their charge and mass, & measure their % abundance.

Ionizing chamber

South pole (-) of magnet attracts lighter isotope more easily than heavier isotope.

Atoms,Molecules,

and Ions

Mass Spectrometer

Mass Spectrum of Germanium (Ge)

Atoms,Molecules,

and Ions

Atomic Mass (Weight): the average mass of isotopes of an element,

considering their natural abundanceIsotope % Abund. f.Abund. X Mass # =

3He 0.01 (0.0001 x 3) = 0.0003

4He 99.99 (0.9999 x 4) = +3.9996

4.000

35Cl 75.77

37Cl 24.23

24Mg 78.99

25Mg 10.00

26Mg 11.01

Atomic Mass (Weigh):

AM = (f1 x M#1) + (f2 x M#2) + …

*

Atoms,Molecules,

and Ions

2007 (B)#2

Atomic Mass (Weigh):

AM = (f1 x M#1) + (f2 x M#2) + …

200?

More exact

Atoms,Molecules,

and Ions

Atoms,Molecules,

and Ions

Properties of Metal, Nonmetals,and Metalloids

Atoms,Molecules,

and Ions

Organization or the Periodic Table: Groups (Families)

The following four groups are known by their names:

Transition Metals

Representative Elements

Representative Elements

Atoms,Molecules,

and Ions

Diatomic Molecules of Elements

These seven + one elements occur naturally as molecules containing two atoms (diatomic).

In compounds they may combine in other ratios. NaCl, BaCl2, AlCl3,CCl4.

At2

Alonso’s Rule of 7 + 1:

•Start with element #7, Nitrogen, trace a 7 and count 7 elements.

•Plus 1 more element, #1 Hydrogen

Atoms,Molecules,

and Ions

Compounds• Pure substances (cannot be separated by

physical means).• Compounds can be broken down

(decomposed) into more elemental particles (elements) by ordinary chemical means.

H2O CO2 H2O2 CO CH4

Molecular Formulas:

Structural Formulas: (Space-filling )

Atoms,Molecules,

and Ions

Classification of Compounds

Covalent (Molecular) Compounds:

Non-Metals + Non-Metals.

Acids: Hydrogen + Nonmetals (polar covalent)

Ionic Compounds

Salts: Metal + Non-Metal

Bases: Metals + Hydroxide Ion (OH-)

Acid Salts: Metal + Acid (Hydrogen + Nonmetal)

Organic Compounds: covalent compounds containing carbon (C) atom chains, with mostly H & O atoms attached to the chain.

Atoms,Molecules,

and Ions

• Composed of a Non-Metal combined with another Non-Metal.

• Are mostly gases, liquids, and sometimes amorphous solids.

• Have low melting points• Bonded atoms share electrons.

Covalent (Molecular) Compounds:

HH22OO(s) (s)

*

HH22OO(l) (l)

HH22OO(g) (g)

Atoms,Molecules,

and Ions

Nomenclature: Molecular Compound

Prefix*- (name of 1st Element)

Prefix- (root of 2nd Element) - IDE

* Prefix mono- not used for 1st element

H2O CO2 H2O2 CO CH4

Molecular Formulas:

Structural Formulas: (Space-filling )

Atoms,Molecules,

and Ions

Ionic Compounds *

Atoms,Molecules,

and Ions

Ionic Compounds (Salts):• Composed of a Metal ion (cation, M+) combined with an Non-

Metal ion (anion, N-); atoms exchange transfer electrons.• Are Crystalline Solids. • Have high melting points• Smallest component particle is called a formula unit, not a

molecule.

Cations

Anions

Atoms,Molecules,

and Ions

(A) Ions with Fixed Charges (Oxidation Numbers)

Zn2+

Cd2+Ag1+

Ionic Nomenclature: Binary Salts

Name of 1st Element Root of 2nd Element -IDE

1+

2+ 3+ 3- 2-

1-

Aluminum Nitride Aluminum Oxide Aluminum Bromide

Al3+ N3- AlN Al3+ O2- Al2O3 Al3+ Br- AlBr3

Atoms,Molecules,

and Ions

Ionic Nomenclature: Binary Salts

Name of 1st Element (Roman Numeral) (or –ous, -ic) Root of 2nd Element -IDE

(B) Ions with Variable Oxidation Numbers (Mostly Transition Metals)

Iron (II) Nitride Iron (III) Nitride

Fe2+ N3- Fe3N2 Fe3+ N3- FeN

Traditional Names:IUPAC Nomenclature:

Atoms,Molecules,

and Ions

Ionic Nomenclature: Binary Salts

• Iron (Ferrum):

Fe 2+ (Iron II or Ferrous) Fe 3+ (Iron III or Ferric) • Copper (Cuprum):

Cu 1+ (Copper I or Cuprous) Cu 2+ (Copper II or Cupric)• Mercury (Hydragyrum):

Hg 1+ (Mercury I or Mercurous) Hg 2+ (Mercury II or Mercuric)

(B) Ions with Variable Oxidation Numbers

ExceptionsExceptions

Atoms,Molecules,

and Ions

Common Representative “-ate” Oxyanions

Ionic Nomenclature: Salts with Polyatomic Ions

Common Polyatomic Ions

NO3 -

nitrate

PO4 3-

phosphate

AsO4 3-

Arsenate

ClO3 -

chlorate

Na+

Na+

Na+

Na+

Atoms,Molecules,

and Ions

Common Representative “-ate” OxyanionsIIIA IVA VA VIA VIIA

BO3 3-

borate

CO3 2-

carbonate

NO3 -

nitrate

Oxygen

SiO3 2-

silicate

PO4 3-

phosphate

SO4 2-

sulfate

ClO3 -

chlorate

AsO4 3-

arsenate

SeO4 2-

sellenate

BrO3 -

bromate

TeO4 2-

tellurate

IO3 -

iodate

Ionic Nomenclature: Salts with Polyatomic Ions

Name of 1st Element (Roman Numeral or –ous, -ic)

Name of Polyatomic ion (all end in -ATE)

Atoms,Molecules,

and Ions

Common Representative “-ate” Oxyanions

IIIA IVA VA VIA VIIA

BO3 3-

borate

CO3 2-

carbonate

NO3 -

nitrate

Oxygen

SiO3 2-

silicate

PO4 3-

phosphate

SO4 2-

sulfate

ClO3 -

chlorate

AsO4 3-

arsenate

SeO4 2-

sellenate

BrO3 -

bromate

TeO4 2-

tellurate

IO3 -

iodate

Pattern in # oxygens:

Per-(oxyanion)-ate

(oxyanion)-ate

(oxyanion)- ite

Hypo-(oxyanion)-ite

Every step down the pattern ion has one less oxygen.

Name of 1st Element (Roman Numeral or –ous, -ic)

Name of Polyatomic ion (Per- Hypo –ATE –ITE)

Polyatomic Ion Mnemonics

ClO3 -

ClO2 -

ClO -

ClO4 -

Atoms,Molecules,

and Ions

Ionic Nomenclature: other Polyatomic Ions

NH4+

ammonium

OH-

hydroxide

CN-

cyanide

SCN-

thiocyanate

C2H3O2-

acetate

MnO4-

permanganate

CrO42-

chromate

Cr2O72-

dichromate

C2O42-

oxalate

O22-

peroxide

Atoms,Molecules,

and Ions

Writing Ionic Formulas

If these subscripts are not in the lowest whole-number ratio, divide them by the greatest common factor.

Mg2+ OH-

Mg 2+ O2-

Mg 2+ PO43-

Mg 2+ SO32-

Mg3(PO4)2

MgOH2

Mg2O2

MgSO3

Mg(OH)2

MgO

Atoms,Molecules,

and Ions

Given Chemical Names, determine Chemical Formula

• Calcium Nitrate

• Iron (III) Hydroxide

• Zinc Phosphate

• Copper (II) Oxide

Ca2+ NO3-

Fe3+ OH-

Zn2+ PO43-

Cu2+ O2-

Ca(NO3)2

Fe(OH)3

Zn3(PO4)2

CuO

Atoms,Molecules,

and Ions

• K2O

• NO2

• KMnO4

• Fe(OH)2

• Cu2O

• Zn(NO3)2

• Cr2(SO3)5

Given Chemical Formula, determine Chemical Names

Potassium Oxide

Nitrogen Dioxide

Potassium Permanganate

Iron (II) Hydroxide

Copper (I) Oxide

Zinc Nitrate

Chromium (V) Sulfite

Atoms,Molecules,

and Ions

Name of Ionic Salt PREFIX- Hydrate

Hydrates (Hydrated Salts)

+ 2H2O

• Ionic substances containing water molecules incorporated into their crystalline structure

• release water upon heating, absorb water under cool, humid conditions

+4 H2O

- 2H2O- 4H2O

Anhydrous

Heat (∆)

H2O H2O

Cu(NO3)2.5H2O

Atoms,Molecules,

and Ions

Acid Nomenclature

Depends on the nomenclature ending of the anion that composes the acid.

• -ide: hydro-(anion root) –ic acidHCl

• -ate: (anion root) -ic acidHNO3

• -ite: (anion root) -ous acid

HNO2

Hydrochloric acid

Nitric acid

Nitrous acid

Acid of Binary -IDE

Acid of Polyatomic

Ion:-ATE -ITE

*

Atoms,Molecules,

and Ions

Acid Nomenclature

• Binary acid ends in -ide, add the prefix hydro- and change the ending to -ic acid HCl: hydrochloric acidHBr: hydrobromic acidHI: hydroiodic acid

Exercises:

• Acid of polyatomic ion ends in -ate, change ending to -ic acidHClO3: chloric acid

HClO4: perchloric acid

HCl, HClO3, HClO4 HBr,

• Acid of polyatomic ion ends in -ite, change the ending to -ous acidHClO2: chlorous acid

HClO: hypochlorous acid

HI, HClO, HClO2

Per-(oxyanion)-ate

(oxyanion)-ate

(oxyanion)- ite

Hypo-(oxyanion)-ite

Atoms,Molecules,

and Ions

Acidic Salts and Basic SaltsAcid Salts: salts of weak polyprotic acids. Are not necessarily acidic, but do neutralize bases.

Basic Salts: salts of weak polyhydroxy bases. They do not dissolve well in water and thus exists mostly in the undissociated solid salt state instead of the dissolved basic state. They do neutralize acids.

Examples:

Acid Salt

HNO3 NaNO3

H2CO3 Na2CO3

H3PO4 Na3PO4

Solubility Rule:• All OH- are insoluble except for IA metals, NH4

+ & slightly soluble Ca 2+ Ba2+ & Sr2+

Mg(OH) 2(s) Fe(OH)3(s) Cr(OH) 3(s))

(Milk of Magnesia)

Acid Salt(s)

-----------

NaHCO3

Na2HPO4 NaH2PO4

sodium hydrogen carbonate

sodium mono-hydrogen phosphate

sodium di-hydrogen phosphate

↔ Cr3+ (aq) + 3 OH-

(aq)

solid salt dissolved (aq) base

Atoms,Molecules,

and Ions

Basic Organic Nomenclature: Alkanes and Alcohols

Name # Carbons Structural Formula

Methane 1 CH4

Ethane 2 CH3CH3

Propane 3 CH3CH2CH3

Butane 4 CH3CH2CH2CH3

Pentane 5 CH3CH2CH2CH2CH3

Hexane 6 CH3CH2CH2CH2CH2CH3

Heptane 7 CH3CH2CH2CH2CH2CH2CH3

Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3

Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3

Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Organic Chemistry: deals with carbon compounds which form long chains of C atoms bonded to other C atoms.

Alkanes: Carbon-hydrogen compounds with single bondsAlcohols: like alkanes, but with organic –OH substituting one H.

Methanol CH3OH

Ethanol CH3CH2OH

Propanol

Butanol

Pentanol

Hexanol

Heptanol

Octanol

Nonanol

Decanol