CHM 1045: General Chemistry and
Qualitative Analysis
Unit 2:
Elements and Compounds:
Atoms, Molecules & Ions
Dr. Jorge L. Alonso
Miami-Dade College –
Kendall Campus
Miami, FL
Textbook References:
•Modules #2 & 5
Atoms,
Molecules,
and Ions
The Early Development of the
Atomic Theory
Atoms,
Molecules,
and Ions
Ancient Atomic Theory
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
Atoms,
them are different shapes and/or arrangements Molecules,
and
and Ions
orientations with respect to each other.
Medieval Alchemy
(‫الخيمياء‬, al-khimia)
Jabir ibn Hayyan
Science as an early form of investigation, with
occult philosophical and spiritual traditions.
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
Atoms,
would cure all diseases and prolong
Molecules,
life indefinitely.
and Ions
Chemistry in the Age of Enlightment
Law of Conservation of Mass:
(1743 - 1794)
(s)
27 g
(l)
(g)
 25 g + 2 g
Atoms,
Molecules,
and Ions
{HgOMovie}
*
Law of Constant Composition
(or Definite Proportions)
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
(1754–1826)
In Water
Ratio H :O
1:8
Compared masses of
different elements within the
same compound.
In H-Peroxide
Ratio H : O
1 :16
Atoms,
Molecules,
and Ions
Dalton’s Law of Multiple
Proportion
John Dalton
(1766–1844).
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
mass Oxygen 32.0 g

 2.67
mass Carbon 12.0 g
C + O2 (low oxy.conc.)  CO
mass Oxygen 16.0 g

 1.33
mass Carbon 12.0 g
2.67 g
 2.00
1.33 g
Atoms,
Molecules,
and Ions
*
Dalton’s Atomic Theory (1801)
•AllAllmatter
1.
matterisismade
madeupupofofsmall
small
indivisible
particles
called
atoms.
indivisible
particles
called
atoms.
•The
2.
Theproperties
propertiesofofthe
theatoms
atomsofofone
one
element
differ
from
those
of of
all all
other
element
differ
form
those
elements.
other elements.
•Atoms
nor
3.
Atomscan
canneither
neither be created
created nor
destroyed.
destroyed.
•All
element are
4.
Allatoms
atomsof
of the
the same
same element
areidentical
identical
in mass,
size,
in mass,
size,
andand
physical
physicalproperties.
properties.
•Atoms
5.
Atomscombine
combineininsmall
smallwhole
whole
number
ratios
to to
form
compounds.
number
ratios
form
compounds.
Atoms,
Molecules,
and Ions
The Electron
Excess of electrons
{Electroscope
Rubber
band
rubs
Movie}
metals
inside
Electrically charged particles can
be rubbed-out of many
substances such as glass
rods, hair, shoes, rubber tires
and shoes. {Electroscope Movie*}
Lack of electrons
Rubber
band
Electric
motor
Van de Graaff
Generator
Atoms,
Molecules,
and Ions
The Electron
Batteries
(chemicals)
Electron
Rays
• cathode ray tubes produce negatively charged
particles (electrons) from chemicals in batteries.
• J. J. Thompson is credited with their
discovery (1897).
Movie 1
Movie 2
Movie 3
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.
4
2
He
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.
Difference
of 105 =
100,000
• Most of the volume of the atom is empty space.
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 were discovered by Rutherford in 1919.
{ProtonDiscoveryMovie}
• Neutrons were discovered by James Chadwick in 1932.
• Protons and neutrons have essentially the same mass.
Atoms,
• The mass of an electron is so small we ignore it.
Molecules,
and Ions
Elements
Pure substances that cannot be broken down into more
elemental particles by ordinary chemical means.
IA
A. Atomic number
B. Mass number
C. Isotopes
D. Atomic mass or weigh
IIA
IIB
IVB
VB
VIB
VIIB
VIII
IIIA
IB
IVA
VA
VIA
VIIIA
VIIA
IIB
Atoms,
Molecules,
and Ions
Elements & Atomic terminology
• Atomic number (Z) = #p
#p = #e- in a neutral atom
Identifies the element
• Mass number (A) = (#p+) + (#no)
A = Z + N
of the same element (same at. #), having
• Isotopes Atoms
different number of neutrons.
• Atomic mass or weigh (a.m.u. or grams)
The average mass of the isotopes of an element,
considering their natural % abundance.
Atoms,
Molecules,
and Ions
*
Isotopes
(atomic
number =1)
• Atoms of the same
element with different
masses (mass number)
• Isotopes have different
numbers of neutrons.
Atomic mass or weigh?
(atomic
number =2)
99.985%
0.015%
0%
Natural Abundance
0.000137%
99.999863%
Natural Abundance
(atomic
number =3)
7.59%
92.41%
Natural Abundance
Isotopes of Carbon: (isotope notation)
Mass number
Atomic number
Natural Abundance:
11
C
6
negligible
12
C
6
98.89%
13
C
6
1.11%
14
C
6
Atoms,
Molecules,
and Ions
negligible
Isotopes of Hydrogen
1H
2H
3H
99.985%
0.015%
negligible
Natural
Abundance
unstable, radioactive
Atoms,
Molecules,
and Ions
Isotopes of Carbon
12C
13C
14C
Natural
Abundance
98.89%
1.11%
negligible
Atoms,
Molecules,
and Ions
Table of Isotopes (partial)
Atoms,
Molecules,
and Ions
Determination of Atomic Mass
Mass spectrometer: can separate isotopes of an element based
on their charge and mass, & measure their % abundance.
South pole (-) of
magnet attracts
lighter isotope more
easily than heavier
isotope.
Ionizing
chamber
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 abundance
*
Isotope % Abund. f.Abund. X Mass # =
3He
0.01
(0.0001 x
4He
99.99
(0.9999 x 4) = +3.9996
3) = 0.0003
4.000
35Cl
75.77
Atomic Mass (Weigh):
37Cl
24.23
AM = (f1 x M#1) + (f2 x M#2) + …
24Mg
78.99
25Mg
10.00
26Mg
11.01
Atoms,
Molecules,
and Ions
200?
2007 (B)#2
More exact
Atomic Mass (Weigh):
AM = (f1 x M#1) + (f2 x M#2) + …
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:
Representative
Elements
Transition Metals
Representative
Elements
Atoms,
Molecules,
and Ions
Diatomic Molecules of Elements
Alonso’s Rule of 7 + 1:
•Start with element #7, Nitrogen, trace a 7 and count 7 elements.
•Plus 1 more element, #1 Hydrogen
At2
These seven + one elements occur naturally as
molecules containing two atoms (diatomic).
In compounds they may combine in other ratios.
NaCl, BaCl2, AlCl3,CCl4.
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.
Molecular Formulas:
H2O
CO2
H2O2
CO
CH4
Atoms,
Molecules,
and Ions
Structural Formulas: (Space-filling )
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 Atoms,
to the
Molecules,
chain.
and Ions
Covalent (Molecular) Compounds:
*
H2O(g)
• 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.
H2O(s)
H2O(l)
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
Molecular Formulas:
H2O
CO2
H2O2
CO
CH4
Atoms,
Molecules,
and Ions
Structural Formulas: (Space-filling )
Ionic Compounds
*
Atoms,
Molecules,
and Ions
Ionic Compounds (Salts):
• Composed of a Metal ion (cation, M+) combined with an NonMetal 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
Atoms,
Molecules,
and Ions
Anions
Ionic Nomenclature: Binary Salts
1+
1-
(A) Ions with Fixed Charges (Oxidation
Numbers)
2+
3+
3-
2-
Zn2+
Ag1+ Cd2+
Aluminum Nitride
Al
3+
3-
N  AlN
Aluminum Oxide
Al
3+
Name of 1st Element
2-
O  Al2O3
Aluminum Bromide
Al
3+
-
Br  AlBr3
Root of 2nd Element
Atoms,
Molecules,
-IDE
and
Ions
Ionic Nomenclature: Binary Salts
(B) Ions with Variable Oxidation Numbers
(Mostly Transition Metals)
Iron (II) Nitride
Fe
2+
IUPAC Nomenclature:
3-
N  Fe3N2
Iron (III) Nitride
Fe
3+
3-
N  FeN
Traditional Names:
Atoms,
Name of 1st Element (Roman Numeral) (or –ous,
-ic)
Molecules,
and Ions
Root of 2nd Element
-IDE
Ionic Nomenclature: Binary Salts
(B) Ions with Variable Oxidation Numbers
• Iron (Ferrum):
Exceptions
2+
3+
Fe (Iron II or Ferrous) Fe (Iron III or Ferric)
• Copper (Cuprum):
Cu 1+ (Copper I or Cuprous) Cu 2+ (Copper II or Cupric)
Atoms,
Molecules,
• Mercury (Hydragyrum):
and Ions
1+
2+
Hg (Mercury I or Mercurous) Hg (Mercury II or Mercuric)
Ionic Nomenclature: Salts with
Polyatomic Ions
Common Representative
“-ate” Oxyanions
Common
Polyatomic Ions
Na+ NO3 nitrate
Na+ PO4 3phosphate
Na+AsO4 3Arsenate
Na+ClO3 chlorate
Atoms,
Molecules,
and Ions
Ionic Nomenclature: Salts with
Polyatomic Ions
Name of 1st Element (Roman Numeral or –ous, -ic)
Name of Polyatomic ion (all end in -ATE)
Common Representative “-ate” Oxyanions
IIIA
IVA
VA
VIA
VIIA
BO3 3borate
CO3 2carbonate
NO3 nitrate
Oxygen
SiO3 2silicate
PO4 3phosphate
SO4 2sulfate
ClO3 chlorate
AsO4 3arsenate
SeO4 2sellenate
BrO3 bromate
TeO4 2tellurate
IO3 iodate
Atoms,
Molecules,
and Ions
Polyatomic Ion Mnemonics
Common Representative
“-ate” Oxyanions
IIIA
IVA
BO3 3CO3 2borate carbonate
SiO3 2silicate
VA
VIA
NO3 nitrate
Oxygen
PO4 3phosphate
AsO4 3arsenate
SO4 2sulfate
VIIA
Pattern in # oxygens:
ClO4 -
Per-(oxyanion)-ate
ClO3 chlorate
ClO3 -
(oxyanion)-ate
ClO2 -
(oxyanion)- ite
SeO4 2BrO3 Hypo-(oxyanion)-ite
sellenate bromate
ClO -
TeO4 2tellurate
IO3 iodate
Every step down the pattern
ion has one less oxygen.
Name of 1st Element (Roman Numeral or –ous, Atoms,
-ic)
Molecules,
and Ions
Name of Polyatomic ion (Per- Hypo –ATE –ITE)
Ionic Nomenclature:
other Polyatomic Ions
OHhydroxide
CNcyanide
SCNthiocyanate
C2H3O2acetate
CrO42chromate
Cr2O72dichromate
C2O42oxalate
O22peroxide
MnO4permanganate
+
NH4
ammonium
Atoms,
Molecules,
and Ions
Writing Ionic Formulas
Mg2+
OH-

MgOH2 Mg(OH)2
Mg 2+
O2-

Mg2O2
Mg 2+
PO43-

Mg3(PO4)2
Mg 2+
SO32-

MgSO3
MgO
Atoms,
 If these subscripts are not in the lowest whole-numberMolecules,
ratio,
and Ions
divide them by the greatest common factor.
Given Chemical Names,
determine Chemical Formula
• Calcium Nitrate
Ca2+
NO3-
Ca(NO3)2
• Iron (III) Hydroxide
Fe3+
OH-
Fe(OH)3
• Zinc Phosphate
Zn2+
PO43-
Zn3(PO4)2
• Copper (II) Oxide
Cu2+
O
2-
CuO
Atoms,
Molecules,
and Ions
Given Chemical Formula,
determine Chemical Names
•
•
•
•
•
•
•
K2O
NO2
KMnO4
Fe(OH)2
Cu2O
Zn(NO3)2
Cr2(SO3)5
Potassium Oxide
Nitrogen Dioxide
Potassium Permanganate
Iron (II) Hydroxide
Copper (I) Oxide
Zinc Nitrate
Chromium (V) Sulfite
Atoms,
Molecules,
and Ions
Hydrates (Hydrated Salts)
• Ionic substances containing water molecules incorporated into their crystalline structure
• release water upon heating, absorb water under cool, humid conditions
H2O
H2O
Heat (∆)
- 4H2O
- 2H2O
+4 H2O
+ 2H2O
Name of Ionic Salt
Cu(NO3)2.5H2O
Anhydrous
PREFIX- HydrateAtoms,
Molecules,
and Ions
*
Acid Nomenclature
Depends on the nomenclature ending of
the anion that composes the acid.
• -ide: hydro-(anion root) –ic acid
 HCl
Hydrochloric acid
Acid of
Binary -IDE
• -ate: (anion root) -ic acid
 HNO3
Nitric acid
• -ite: (anion root) -ous acid
 HNO2
Nitrous acid
Acid of
Polyatomic
Ion:-ATE -ITE
Atoms,
Molecules,
and Ions
Acid Nomenclature
Exercises: HCl, HClO3, HClO4 HBr, HI, HClO, HClO2
• Binary acid ends in -ide, add the prefix hydro- and change
the ending to -ic acid
 HCl: hydrochloric acid
 HBr: hydrobromic acid
 HI: hydroiodic acid
• Acid of polyatomic ion ends in -ate, change ending to -ic acid
Per-(oxyanion)-ate
 HClO3: chloric acid
(oxyanion)-ate
 HClO4: perchloric acid
(oxyanion)- ite
Hypo-(oxyanion)-ite
• Acid of polyatomic ion ends in -ite, change the ending to
-ous acid
Atoms,
Molecules,
 HClO2: chlorous acid
and Ions
 HClO: hypochlorous acid
Acidic Salts and Basic Salts
Acid Salts: salts of weak polyprotic acids. Are not necessarily acidic, but do neutralize bases.
Examples:
Acid
Salt
Acid Salt(s)
HNO3
NaNO3
-----------
H2CO3
Na2CO3
NaHCO3  sodium hydrogen carbonate
H3PO4
Na3PO4
Na2HPO4
NaH2PO4  sodium di-hydrogen
sodium mono-hydrogen
phosphate
phosphate
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.
Mg(OH) 2(s)
(Milk of Magnesia)
Fe(OH)3(s)
Cr(OH)
3(s))
solid salt
3+
↔ Cr
(aq) +
3 OH
(aq)
dissolved (aq) base
Atoms,
Molecules,
and Ions
Solubility Rule:
•
All OH- are insoluble except for IA metals, NH4+ & slightly soluble Ca 2+ Ba2+ & Sr2+
Basic Organic Nomenclature:
Alkanes and Alcohols
Organic Chemistry: deals with carbon compounds which form long chains of C
atoms bonded to other C atoms.
Alcohols: like alkanes,
Alkanes: Carbon-hydrogen compounds with single bonds
Name
# Carbons
but with organic –OH
substituting one H.
Structural Formula
Methane
1
CH4
Methanol CH3OH
Ethane
2
CH3CH3
Ethanol CH3CH2OH
Propane
3
CH3CH2CH3
Propanol
Butane
Pentane
4
5
CH3CH2CH2CH3
CH3CH2CH2CH2CH3
Butanol
Hexane
6
CH3CH2CH2CH2CH2CH3
Heptane
7
CH3CH2CH2CH2CH2CH2CH3
Octane
8
CH3CH2CH2CH2CH2CH2CH2CH3
Nonane
9
CH3 CH2 CH2CH2CH2CH2CH2CH2CH3
Decane
10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
Pentanol
Hexanol
Heptanol
Octanol
Atoms,
Nonanol Molecules,
and Ions
Decanol