The Components of Matter
Chapter 2
Chapter 2; Atoms, Molecules,
and Ions
I.
Atomic Structure
a.
b.
II.
Cathode Ray Tube
Rutherford Scattering Experiment
Atomic Number, Mass Number,
Isotopes, and Ions
III. Period Trends
IV. Naming and Classifying Compounds
V. Molecular vs. Empirical Formulas
The Electron
• Streams of negatively charged particles were
found to emanate from cathode tubes.
• J. J. Thompson is credited with their discovery
(1897).
The Electron
Thompson measured the charge/mass ratio of the
electron to be 1.76 × 108 coulombs/g.
Millikan Oil Drop Experiment
Once the charge/mass
ratio of the electron was
known, determination of
either the charge or the
mass of an electron
would yield the other.
Millikan Oil Drop Experiment
Robert Millikan
(University of Chicago)
determined the charge on
the electron in 1909.
Radioactivity:
• The spontaneous emission of radiation by
an atom.
• First observed by Henri Becquerel.
• Also studied by Marie and Pierre Curie.
Radioactivity
• Three types of radiation were discovered by
Ernest Rutherford:
α particles
β particles
γ rays
Subatomic Particles
Particle
Mass
(g)
Charge
(Coulombs)
Charge
(units)
Electron (e-) 9.1 x 10-28 -1.6 x 10-19
-1
Proton (p+)
+1
1.67 x 10-24 +1.6 x 10-19
Neutron (n) 1.67 x 10-24
0
0
−24

Nucleonmass  1.67 x10 g  1830
=
=
−
28
Electronmass  9.11x10 g 
1
12C is the reference mass: 1 amu = 1/12 mass of 12C
Rutherford’s Model of
the Atom
atomic radius ~ 100 pm = 1 x 10-10 m
nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m
Atomic number (Z) = number of protons in nucleus (identity of
the element)
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Mass Number
A
Element Symbol
X
Atomic Number
Z
1
1H
235
92
2
1H
U
(D)
238
92
3
1H
(T)
U
Isotopes are atoms of the same element (X) with different
numbers of neutrons in their nuclei
The number of protons is constant these are all hydrogen
Isotopes
mass # –protons = neutrons
How many protons, neutrons, and electrons are in 146
C?
6 protons, 8 (14 - 6) neutrons, 6 electrons
How many protons, neutrons, and electrons are in 116
6 protons, 5 (11 - 6) neutrons, 6 electrons
C?
Change the
Number of….
You’ll get a
different….
Protons
Element
Neutrons
Isotope
Electrons
Ion
Natural lithium is:
7.42% 6Li (6.015 amu)
92.58% 7Li (7.016 amu)
Average atomic mass of lithium:
(7.42 x 6.015) + (92.58 x 7.016) = 6.941 amu
100%
(.0742 x 6.015)+(.9258 x 7.016)= 6.941 amu
The average weight of atoms in a distribution of isotope atoms found
in nature is determined by multiplying each mass by its percentage
abundance and summing all the products:
=
mass
n
∑ mass ⋅ fractional abundace
i =1
i
General Division of Compounds
Compounds
Organic Compounds
Originally from “living matter”
Inorganic Compounds
Metals and other elements
Form inorganic compounds
i.e. “non-living matter”
Covalent Compounds
[Sharing of Electrons]
Formation of a Covalent Bond between Two H Atoms
Inorganic Compounds
Ionic
Molecular
Aqueous Acid
Bases
An ion is an atom, or group of atoms, that has a net
positive or negative charge.
cation – ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation.
Na
11 protons
11 electrons
Na+
11 protons
10 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.
Cl
17 protons
17 electrons
Cl-
17 protons
18 electrons
A monatomic ion contains only one atom
Na+, Cl-, Ca2+, O2-, Al3+, N3-
A polyatomic ion contains more than one atom
OH-, CN-, NH4+, NO3-
Ions
+
27
3
How many protons and electrons are in 13 Al ?
13 protons, 10 (13 – 3) electrons
2- ?
Se
How many protons and electrons are in 78
34
34 protons, 36 (34 + 2) electrons
Noble Gas
Halogen
Group
Alkali Metal
Alkali Earth Metal
Period
Predicting Ion Charges
• Metal Atoms Produce Positive Ions
• Family A; Charge = Group #
• Family B; Charge is Positive but Variable
• Nonmetal Atoms Produce Negative Ions
• Charge = Group # - 8
Common Monatomic Ions
Charge
+1
+2
+3
Cations
Formula
Name
H+
Anions
Formula
Name
hydrogen
H-
hydride
Li+
lithium
F-
fluoride
Na+
sodium
Cl-
chloride
K+
potassium
Br-
bromide
Cs+
cesium
I-
iodide
Ag+
silver
Mg2+
magnesium
oxide
Ca2+
calcium
O2-
sulfide
Sr2+
strontium
S2-
Ba2+
barium
Zn2+
zinc
Cd2+
cadmium
Al3+
aluminum
Charge
-1
-2
Common ions are in blue.
-3
N3-
nitride
Metals With Several Oxidation
States
Element
Copper
Cobalt
Iron
Manganese
Tin
Ion Formula
Systematic Name
Common Name
Cu+1
copper(I)
cuprous
Cu+2
copper(II)
cupric
Co+2
cobalt(II)
Co+3
cobalt (III)
Fe+2
iron(II)
ferrous
Fe+3
iron(III)
ferric
Mn+2
manganese(II)
Mn+3
manganese(III)
Sn+2
tin(II)
stannous
Sn+4
tin(IV)
stannic
1. Please give the name (correct spelling) of the element whose symbol is listed:
F ______________
Si_______________
Na _____________
Ne ______________
2. Perform the following calculation and report your answer to the correct number
of significant figures:
14.678 - 12.322 + 7.45 =
3. Perform the following calculation and report your answer to the correct number
of significant figures:
4.6 + 12.3 /5.06
4. You should know that there are roughly 2.2 pounds in a kilogram (useful when
you travel outside the U.S.). If there are exactly 7000 grains in a pound, how many
grams are represented by 20. grains?
ionic compounds consist of a combination of cations
and an anions
• the formula is always the same as the empirical formula
• the sum of the charges on the cation(s) and anion(s) in each
formula unit must equal zero
The ionic compound NaCl
Formula of Ionic Compounds
2 x +3 = +6
3 x -2 = -6
Al2O3
Al3+
1 x +2 = +2
Ca2+
1 x +2 = +2
Na+
O22 x -1 = -2
CaBr2
Br1 x -2 = -2
Na2CO3
CO32-
A molecular formula shows the exact number of
atoms of each element in the smallest unit of a
substance
An empirical formula shows the simplest
whole-number ratio of the atoms in a substance
molecular
empirical
H2O
H2O
C6H12O6
CH2O
O3
O
N2H4
NH2
Chemical Formulas
The subscript to the right of
the symbol of an element
tells the number of atoms of
that element in one
molecule of the compound.
Molecular Compounds
Molecular compounds are
composed of molecules and
almost always contain only
nonmetals.
Law of Conservation of Mass:
.
The total mass of substances does not
change during a chemical reaction
reactant 1
+
total mass
calcium oxide
CaO
product
reactant 2
+
+
=
carbon dioxide
CO2
total mass
calcium carbonate
CaCO
3
56.08g
+
44.00g
100.08g
Calculating the Mass of an Element in a Compound
Ammonium Nitrate
How much nitrogen(N) is in 455kg of ammonium nitrate?
ammonium nitrate =
NH4NO3Mass of Cpd is:
The Formula
4 x H = 4 x 1.008 = 4.032 g
2 x N = 2 X 14.01 = 28.02 g
3 x O = 3 x 16.00 = 48.00 g
Therefore g nitrogen/g cpd
28.02g N
= 0.3500gN/g cpd
80.052g cpd
80.052 g
455kg x 1000g/kg = 455,000g NH4NO3
455,000g cpd x 0.3500g N/g cpd = 1.59 x 105g nitrogen
or:
28.02 kg nitrogen
455 kg NH4NO3 X
= 159 kg Nitrogen
80.052 kg NH4NO4
Chemical Nomenclature
Compounds
• Ionic Compounds
– often a metal + nonmetal
– Name positive ion; then negative ion
– Don’t state the number of ions in name
Naming Ions
–Name of monoatomic metal cation is metal name
–Name of monoatomic anion (nonmetal), add
“ide”to element stem
–Name of polyatomic ion ; read off chart
Some Common Polyatomic Ions
Formula
Name
Formula
Name
H3O+
hydronium
Cations
NH4
+
ammonium
Common Anions
CH3COO-
acetate
CO3-2
carbonate
CN-
cyanide
CrO4-2
chromate
OH-
hydroxide
Cr2O7-2
dichromate
ClO3-
chlorate
O2-2
peroxide
NO2-
nitrite
SO4-2
sulfate
NO3-
nitrate
PO4-3
phosphate
MnO4-
permanganate
Oxoanions, Hydrates & Binary Covalent Compounds
No. of O atoms
Naming oxoanions
Prefixes
Root
Suffixes
per
root
ate
ClO4-
perchlorate
root
ate
ClO3-
chlorate
root
ite
ClO2-
chlorite
root
ite
ClO-
hypochlorite
hypo
Examples
Numerical Prefixes for Hydrates and Binary Covalent Compounds
Number
Prefix
Number
Prefix
Number
1
mono
4
tetra
8
octa
2
di
5
penta
9
nona
3
tri
6
hexa
10
deca
7
hepta
Prefix
Oxy Acids
• Formed by the combination of hydrogen
and most polyatomic ions
• Name after the root of the anion plus the
following endings:
• -ic acid if the polyatomic ion ended with –
ate
• -ous if the anion ended with –ite
• Mineral acids use common names
Oxyacids
•
•
•
•
•
•
•
•
C2H3O2- acetate ion
CO32- carbonate ion
NO3- nitrate ion
PO43- phosphate ion
ClO- hypochlorite ion
ClO2- chlorite ion
ClO3- chlorate ion
ClO4- perchlorate ion
•
•
•
•
•
•
•
•
HC2H3O2 acetic acid
H2CO3 carbonic acid
HNO3 nitric acid
H3PO4 phosphoric a.
HClO hypochlorous a.
HClO2 chlorous acid
HClO3 chloric acid
HClO4 perchloric acid
Determining Names and Formulas of
Ionic Compounds Containing
Polyatomic Ions
PROBLEM: Give the systematic names or the formula or the formulas for the
names of the following compounds:
(a) Fe(ClO4)2
PLAN:
(b) sodium sulfite
(c) Ba(OH)2 8H2O
Note that polyatomic ions have an overall charge so when writing a
formula with more than one polyatomic unit, place the ion in a set of
parentheses.
SOLUTION:
(a) ClO4- is perchlorate; iron must have a 2+ charge. This is iron(II)
perchlorate.
(b) The anion sulfite is SO32- therefore you need 2 sodiums per sulfite.
The formula is Na2SO3.
(c) Hydroxide is OH- and barium is a 2+ ion. When water is included in
the formula, we use the term “hydrate” and a prefix which indicates the
number of waters. So it is barium hydroxide octahydrate.
Some Polyatomic Ions
NH4+
ammonium
SO42-
sulfate
CO32-
carbonate
SO32-
sulfite
bicarbonate
NO3
-
nitrate
ClO3-
chlorate
NO2-
nitrite
Cr2O72-
dichromate
SCN-
thiocyanate
HCO3
CrO4
-
2-
chromate
-
OH
hydroxide
Chemical Nomenclature
Compounds
Mg(OH)2
magnesium hydroxide
KNO3
potassium nitrate
K2O
potassium oxide
Transition metal ionic compounds
– indicate charge on metal with Roman numerals
(Stock Method)
FeCl2
2 Cl- = -2, so Fe is +2
iron(II) chloride
FeCl3
3 Cl- = -3, so Fe is +3
iron(III) chloride
Cr2S3 3 S-2 = -6, so Cr is +3 (6/2)
chromium(III) sulfide
Chemical Nomenclature
molecular Compounds
• State the number of atoms in the name
(formula can not be predicted).
• State name of first nonmetal atom in the
first word; second word is second nonmetal
stem + -ide. Use Greek prefixes when
appropriate.
Molecular Compounds
HI
hydrogen iodide
NF3
nitrogen trifluoride
SO2
sulfur dioxide
N2Cl4
dinitrogen tetrachloride
NO2
nitrogen dioxide
N2O
dinitrogen monoxide
TOXIC!
Laughing Gas
Chemical Nomenclature
Compounds
AQUEOUS ACIDS
Binary Aqueous Acids
hydro+nonmetal stem +-ic Acid
Ternary Aqueous Acids
Nonmetalstem -ic Acid
Chemical Nomenclature
Compounds
BASES
Name like ionic compounds; Don’t state # of
ions
•
•
Name + ion in first word
Second word is hydroxide
Sodium Hydroxide: NaOH