Prof.H.A.Mohammed
General Chemistry – Chem 101
Taibah University
Faculty of Science and Arts
Chemistry Department
General
Chemistry
Chem. 101
For
Chemistry , Physics and Biology
Students
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
General Chemistry (101 Chem.)
Course Description
Syllabus : The course will cover the following topics
:‫ﻳﺣﺗﻭﻱ ﺍﻟﻣﻘﺭﺭﻋﻠﻰ ﺍﻟﻣﻭﺿﻭﻋﺎﺕ ﺍﻟﺗﺎﻟﻳﺔ‬
U
‫• ﺍﻻﺳﺱ ﺍﻟﻛﻳﻣﻳﺎﺋﻳﺔ‬
1-Chemical Foundations
‫• ﺍﻟﺫﺭﺍﺕ ﻭﺍﻟﺟﺯﻳﺋﺎﺕ ﻭﺍﻻﻳﻭﻧﺎﺕ‬
2-Atoms, Molecules and Ions
‫• ﺍﻟﺣﺳﺎﺑﺎﺕ ﺍﻟﻛﻳﻣﻳﺎﺋﻳﺔ‬
3-Stoichiometry
‫ﺍﻧﻭﺍﻉ ﺍﻟﺗﻔﺎﻋﻼﺕ ﺍﻟﻛﻳﻣﻳﺎﺋﻳﺔ‬
4-Types of Chemical Reactions
‫• ﺍﻟﺑﻧﺎء ﺍﻟﺫﺭﻱ ﻭﺍﻟﺗﺻﻧﻳﻑ ﺍﻟﺩﻭﺭﻱ‬
5-Atomic Structure and
Periodicity
‫• ﺍﻟﺗﺭﺍﺑﻁ ﺍﻟﻛﻳﻣﻳﺎﺋﻲ‬
6-Chemical Bonding
Prof.H.A.Mohammed
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General Chemistry – Chem 101
U
Prof.H.A.Mohammed
General Chemistry – Chem 101
Chapter 1: Chemical Foundations
Chemistry: An overview
1.1 The Scientific Method
1.2 Units of Measurement
1.3 Uncertainty in Measurement
1.4 Significant Figures and Calculations
1.5 Dimensional Analysis
1.6 Temperature
1.7 Classification of Matter
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Chemical Foundations
Chemistry: An overview
‫ﻣﻘﺩﻣﺔ‬:‫ﺍﻟﻛﻳﻣﻳﺎء‬
1.1 The Scientific Method
‫ﺍﻟﻁﺭﻳﻘﺔ ﺍﻟﻌﻠﻣﻳﺔ‬
1.2 Units of Measurement
‫ﻭﺣﺩﺍﺕ ﺍﻟﻘﻳﺎﺱ‬
‫ﺍﻟﺷﻙ ﻓﻲ ﺍﻟﻘﻳﺎﺱ‬
1.3 Uncertainty in Measurement
Chemistry: An overview:
U
• An Observational Science
• An Experimental Science
• A Laboratory Science
• An Interesting Science
• An Important Science
• A “Hard” Science
What Is Chemistry?
U
The Study of Matter and its Properties, the Changes that Matter
Undergoes, and the Energy Associated with those Changes.
For example: Oxygen atom, hydrogen atom, water molecule
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Water turning to oxygen and hydrogen
Everything is made of tiny particles called atoms and molecules.
Chemists study these particles, looking at the kinds, numbers, structure,
size which produce varying chemical and physical properties
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Humans are by nature curious.
Science is just exploring nature.
A scientists is just a person exploring.
You begin to organize your thoughts into Observation, you group those
observations into Hypotheses, using Experimentation, and formulate
Laws or Theories
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
1.1 Steps in the Scientific Method
1--Observations
• quantitative : water boils at 100C
• qualitative: the sky is blue, water is liquid
2.Formulating hypotheses
• possible explanation for the observation
3.Performing experiments : gathering new information to
decide whether the hypothesis is valid Theory (Model)
• A set of tested hypotheses that give an overall
explanation of some natural phenomenon.
Natural Law
The same observation applies to many different systems
Example - Law of Mass Conservation “In a chemical
reaction matter is either created nor destroyed.”
Speed of Light, E = mc2
Law vs. Theory
A law summarizes what happens;
A theory (model) is an attempt to explain why it happens.
Laws : Very specific, “What will happen” often expressed
in mathematical equations.
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Theories: Very general, “Why it will happen,” often includes
many “Laws
1.2 Units of Measurement
The Fundamental SI Units
Physical Quantity
Name of Unit
Abbreviation
Mass
kilogram
kg
Length
meter
m
Time
second
s
Temperature
kelvin
K
Electric current
ampere
A
Amount of substance
mole
mol
Luminous intensity
candela
cd
Prefixes Used to Modify Standard Unit
1. kilo = 1000 times base unit = 103
k=1000
or
k = 103
1 kg = 103g
• nano = 10-9 times the base unit
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
n = 10-9
n=.000000001 or
1 nL = 10-9L
Information
2 significant figures
7.8 km Given:
? mi Find:
Conversion Factor:1 km = 0.6214 mile
0.6214 mi
km → mi Solution Map:
1 km
Example:
Convert 7.8 km to
miles.
Apply the solution map: •
7.8 km ×
0.6214 mile
= mi
1 km
= 4.84692 mi
Significant figures and round:•
= 4.8 mi
2 significant figures
۲۰
Tro's "Introductory Chemistry",
Chapter 2
A digit that must be estimated is called uncertain.
A measurement always has some degree of uncertainty
Precision and Accuracy
Accuracy refers to the agreement of
a particular value with the true value.
‫ﻣﺩﻯ ﺗﻁﺎﺑﻕ ﺍﻟﻘﺭﺍءﺓ ﺍﻟﻣﻘﺎﺳﺔ ﻣﻊ ﺍﻟﻘﺭﺍءﺓ ﺍﻟﺻﺣﻳﺣﺔ‬
Precision refers to the degree of agreement
among several elements of the same quantity.
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
‫ﻣﺩﻯ ﺗﻁﺎﺑﻕ ﺍﻟﻘﺭﺍءﺍﺕ ﺍﻟﻣﻘﺎﺳﺔ ﻣﻊ ﺑﻌﺿﻬﺎ ﺍﻟﺑﻌﺽ‬
‫ﺑﻌﺾ ﺍﻻﺩﻭﺍﺕ ﺍﻟﻤﻌﻤﻠﻴﺔ ﺍﻟﻤﺴﺘﺨﺪﻣﺔ ﻟﻘﻴﺎﺱ ﺍﻟﺤﺠﻢ‬
۲۲
Prof.H.A.Mohammed
Prepared by Dr. Amjad Shraim and Dr.
Fethi Kooli
10
General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
The difference between accuracy
and precision
‫ﻋﺪﻡ ﺍﻟﺼﺤﺔ ﻭ ﻋﺪﻡ ﺍﻟﺪﻗﺔ‬
‫ﺍﻟﻔﺮﻕ ﺑﻴﻦ ﺍﻟﺪﻗﺔ ﻭﺍﻟﺼﺤﺔ‬
‫ﺍﻟﺪﻗﺔ‬
‫ﺍﻟﺼﺤﺔ ﻭ ﺍﻟﺪﻗﺔ‬
۲۳
1.4 Significant Figures and Calculations
Rules for Counting significant figures
1-Non-Zero integers
2-Zeros:
(a)Leading zeros
(b) Capitive zero
(c) trailing zeros
3. Exact numbers
1-Nonzero integers always count as significant figures
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
2-Zeros
(a)Leading zeros do not count as significant figures.
(b)Captive zeros always count as significant figures
16.07 has 4 sig.figs
(c) Trailing zeros are significant only if t the number contains
a decimal point.
9.300 has 4 sig figs
3-Exact numbers have an infinite number of significant figures
1 inch = 2.54 cm, exactly
Multiplication and Division
# sig figs in the result equals the number in the least precise
measurement used in the calculation.
6.38 x 2.0 =12.76
13 (2 sig figs)
Addition and Subtraction:
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
# sig figs in the result equals the number of decimal places in
the least precise measurement.
6.8 + 11.934 =
22.4896 ~ =22.5
(3 sig. figs)
Numbers
1-Exact
2-Measured: Significant Figures
• Exact: Sometimes you can determine an exact value for a quality
of an object.
• Often by counting.
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
• Books on a table.
• Sometimes by definition
• 1 cm is exactly 1/100th of 1 meter.
• Measured: Whenever you use an instrument to compare a quality
of an object to a standard, there is uncertainty in the comparison.
Writing a Number in Scientific Notation, Continued
0.00012340
1.
Locate the decimal point.
0.00012340
2.
Move the decimal point to obtain a number between 1 and 10.
1.2340
3.
Multiply the new number by 10n .
• Where n is the number of places you moved
the decimal point.
1.2340 x 104
4.
If you moved the decimal point to the left, then n is +;
if you moved it to the right, then n is − .
1.2340 x 10-4
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Writing a Number in Standard Form: ( 1.234 x 10-6 )
• Since exponent is -6, make the number smaller by moving the
decimal point to the left 6 places.
• When you run out of digits to move around, add zeros.
• Add a zero in front of the decimal point for decimal numbers.
000 001.234
0.000 001 234
How many sig figs?
45.8736
6
•All digits count
0.000239
3
•Leading 0’s don’t
0.00023900
5
•Trailing 0’s do
48000.
5
•0’s count in decimal form
48000
2
•0’s don’t count w/o decimal
3.982×106
4
•All digits count
1.00040
6
•0’s between digits count as well
as trailing in decimal form
Rounding
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
When rounding to the correct number of significant figures, if the number
after the place of the last significant figure is:
0 to 4, round down.
Drop all digits after the last significant figure and leave the last significant
figure alone.
5 to 9, round up.
Drop all digits after the last significant figure and increase the last
significant figure by one
1.5 Dimensional
Analysis
‫ﺍﻟﺘﺤﻮﻳﻞ ﺑﻴﻦ ﺍﻟﻮﺣﺪﺍﺕ ﺍﻟﻤﺨﺘﻠﻔﺔ‬
Proper use of “unit factors” leads to
proper units in your answer.
OK:
NOT OK:
1 kilometer
0.62137 mile
=
0.62137 mile
1 kilometer
1 kilometer
1 mile
=
0.62137 mile
0.62137 kilometer
Copyright©2000 by Houghton Mifflin
Company. All rights reserved.
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Temperature Scales and Interconversions
Kelvin ( K ) - The “Absolute temperature scale” begins at
absolute zero and only has positive values.
Celsius ( oC ) - The temperature scale used by science,
formally called centigrade and most
commonly used scale around the world.
Water freezes at 0oC, and boils at 100oC.
Fahrenheit ( oF ) - Commonly used scale in America for
our weather reports. Water freezes at 32oF,
and boils at 212oF.
T (in K) = T (in oC) + 273.15
T (in oF) = 9/5 T (in oC) + 32
T (in oC) = T (in K) - 273.15
T (in oC) = [ T (in oF) - 32 ] 5/9
Problem 3-8:Temperature Conversions
(a) The boiling point of Liquid Nitrogen is -195.8 oC, what is
the temperature in Kelvin and degrees Fahrenheit?
T (in K) = T (in oC) + 273.15
T (in K) =
T (in oF) = 9/5 T (in oC) + 32
T (in oF) =
(b)The normal body temperature is 98.6oF, what is it in Kelvin
and degrees Celsius?
T (in oC) = [ T (in oF) - 32] 5/9
T (in oC) =
T (in K) = T (in oC) + 273.15
T (in K) =
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
1.6 Density
• Inverse relationship between mass and volume.
• Solids = g/cm3
– 1 cm3 = 1 mL
Density =
Mass
Volume
• Liquids = g/mL
• Gases = g/L
• Volume of a solid can be determined by water
displacement—Archimedes Principle.
• Density : solids > liquids > gases
– Except ice is less dense than liquid water!
٥٦
1.7 Clssification of Matter
Any matter can exist in one of 3 States
• (a) Gas
Prof.H.A.Mohammed
(b) Liquid
(c) Solid
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Solids
• The particles in a solid are packed
close together and are fixed in
position.
– Although they may vibrate.
• The close packing of the particles
results in solids being
incompressible.
• The inability of the particles to
move around results in solids
retaining their shape and volume
when placed in a new container
and prevents the particles from
flowing.
Tro's "Introductory Chemistry",
Chapter 3
Liquids
• The particles in a liquid are closely packed,
but they have some ability to move around.
• The close packing results in liquids being
incompressible.
• The ability of the particles to move allows
liquids to take the shape of their container
and to flow. However, they don’t have
enough freedom to escape and expand to
fill the container.
٦۳
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Matter: is it pure or impure
Matter
Mixture
Pure Substance
Constant Composition
Variable Composition
Heterogeneous
Homogeneous
• Pure Substance = All samples are made of the same
pieces in the same percentages.
– Salt
• Mixtures = Different samples may have the same pieces in
different percentages.
– Salt water
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Mixtures
Heterogeneous
Homogeneous
1. Made of multiple
substances,
whose presence
can be seen.
2. Portions of a
sample have
different
composition and
properties.
1. Made of multiple
substances, but
appears to be one
substance.
2. All portions of a
sample have the
same composition
and properties.
Tro's "Introductory Chemistry",
Chapter 3
٦٦
Matter Summary
٦۷
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General Chemistry – Chem 101
Prof.H.A.Mohammed
Prof.H.A.Mohammed
General Chemistry – Chem 101
22
General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
• Matter has PropertiesPhysical Properties are the
characteristics of matter that can be changed without
changing its composition.
A.Characteristics that are directly observable.
• Chemical Properties are the characteristics that determine
how the composition of matter changes as a result of
contact with other matter or the influence of energy.
A.Characteristics that describe the behavior of matter.
Matter has Properties, Matter can also go through
Changes
• Changes that alter the state or appearance of the matter
without altering the composition are called physical
changes.
• Changes that alter the composition of the matter are called
chemical changes.
A.During the chemical change, the atoms that are present
rearrange into new molecules, but all of the original
atoms are still present.
Is it a Physical or Chemical Change?
– A physical change results in a different form of the same
substance.
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
– The kinds of molecules don’t change.
– A chemical change results in one or more completely new
substances.
– Also called chemical reactions.
– The new substances have different molecules than the
original substances.
You will observe different physical properties because
the new substances have their own physical properties
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Chapter :2
Atoms, Molecules and Ions
1-Fundamental Chemical Laws
1-Conservation of Mass
2-Definite Composition
3-Law of Multiple Proportions
2-Early Experiments To Characterize Atom
3-The Periodic Table
4-Naming Simple Compounds
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Lecture :1
1-Fundamental Chemical Laws :
Three Laws that Led to the Atomic Theory
• Law of Mass Conservation: The total mass of substances does not
change during a chemical reaction (Lavoisier).
• Law of Definite ( or Constant ) Composition: No matter what its
source, a particular chemical compound is composed of the same
elements in the same parts (fractions) by mass (Proust).
• The Law of Multiple Proportions: When two elements form a
series of compounds, the masses of one element that combine
with a fixed mass of the other element are in the ratio of small
integers to each other (Dalton).
1-Conservation of Mass
• Matter is neither created nor destroyed in a chemical reaction.
• In every chemical operation an equal quantity of matter exists
before and after the operation.
• Mass is conserved in a chemical reaction.
• Moreover, in chemical change, the mass of the elements is
conserved, element by element.
• Development of this law was made possible by the analytical
balance.
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Problem
• Potassium chlorate (KClO 3 ) decomposes to potassium chloride
(KCl) and oxygen (O 2 ) when heated. In one experiment 100.0
g of KClO 3 generated 36.9g of O 2 and 57.3 g of KCl. What
mass of KClO 3 remained unreacted?
• Mass of KClO 3 before reaction = mass of KCl + mass of O 2
+ mass of unreacted KClO 3
• 100.0 g of KClO 3 = 57.3 g KCl + 36.9g O 2 + g unreacted KClO 3
• g unreacted KClO 3 = 100.0 g - 57.3 g - 36.9 g = 5.8 g
2-Definite Composition
Chemical analysis of a 9.07 g sample of calcium phosphate shows
that it contains 3.52 g of Ca.
How much Ca could be obtained from a 1.000 kg
sample?
Mass fraction Ca = 3.52 g Ca / (9.07 g total) = 0.388
(i.e., 38.8% Ca by mass in any sample of compound)
Mass Ca in 1.000 kg =
(1.000 kg total)x(0.388 g Ca/ g total) = 0.388 kg C
= 388 g Ca
2-Law of Definite Proportions
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
In a given chemical compound, the proportions by mass of the
elements that compose it are fixed, regardless of the source of the
compound.
The ratio of elements in a compound is fixed regardless of the source
of the compound.
Water is made up of 11.1% by mass of hydrogen and 88.9% oxygen.
3-Law of Multiple Proportions
If elements A and B react to form two compounds,the different
masses of B that combine with a fixed mass of A can be expressed as
a ratio of small whole numbers.
Example: Nitrogen Oxides I & II
Cmpd
Mass %
N
Mass %
O
Mass Ratio
O/N
Ratio of
Ratios
I
46.68
53.32
1.142
1
II
30.45
69.55
2.284
2
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Law of Multiple Proportions (Dalton)
•
If elements A & B react to form more than one compound, the different
masses of “B” that combine with a fixed mass of “A” can be expressed as a
ratio of SMALL WHOLE NUMBERS.
Ex. Assume two compounds containing just Carbon (C) and Oxygen (O)
with the following relative compositions
Carbon Oxide (I): 57.1 % Oxygen and 42.9 % Carbon
Carbon Oxide (II): 72.7 % Oxygen and 27.3 % Carbon
Mass Ratios: Oxide (I)
= 57.1 / 42.9 C = 1.33 g O / g C
Oxide (II) = 72.7 / 27.3 C = 2.66 g O / g C
Ratio Oxide (I) / Oxide (II) = 1.33 / 2.66 = 1/2
Expressing the relative mass fractions as “small whole numbers”, the ratio of
oxygen atoms to carbon atoms in Oxide I is 1:1 (CO)
The ratio of oxygen atoms to carbon atoms in Oxide II is 2:1 (CO2)
14
Dalton’s Atomic Theory
• Matter is composed of (indivisible) atoms.
• All atoms of a given chemical element are identical in mass and in
all other properties.
• Different chemical elements are composed of different atoms of
different masses.
• Atoms are indestructible. They retain their identities in a chemical
reaction.
• A compound forms from its elements through the combination of
atoms of unlike elements in small whole number ratios.
• Matter is composed of (indivisible) atoms.
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
• All atoms of a given chemical element are identical in mass and in
all other properties.
• Different chemical elements are composed of different atoms of
different masses.
• Atoms are indestructible. They retain their identities in a chemical
reaction.
• A compound forms from its elements through the combination of
atoms of unlike elements in small whole number ratios.
• Matter is composed of (indivisible) atoms.
• All atoms of a given chemical element are identical in mass and in
all other properties.
• Different chemical elements are composed of different atoms of
different masses.
• Atoms are indestructible. They retain their identities in a chemical
reaction.
• A compound forms from its elements through the combination of
atoms of unlike elements in small whole number ratios.
Early Experiments To Characterize The Atom
Experiencing Atoms
1. There are about 91 elements found in nature.
– Over 20 have been made in laboratories.
(a) Each kind of atom is unique
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
a. Carbon is not Hydrogen
b. They have different properties
i. Structure, magnetic meaning they can attract and repel
other atoms, melting, boiling, electrical, stability,
reactivity (attract and repel), etc…
The Atom Is Divisible
• Work done by J. J. Thomson and others proved that the atom had
pieces(subatomic particles) called electrons.
• Thomson found that electrons are much smaller than atoms and
carry a negative charge.
– The mass of the electron is 1/1836th the mass of a hydrogen
atom.
– The charge on the electron is the fundamental unit of charge
that we call –1 charge unit.
The Electron
1- A Glass tube from which most of the air has been evacuated.
2-When two metal plates are connected to a high –voltage source, the
negatively charged plate, called the cathode, emits an invisible ray.
3- The cathode ray is drawn to the positively charged plate, called the
anode, where it passes through a hole and continues travelling to the
other of the tube
4-When the ray strikes the specially coated surface, it produces a
strong fluorescence, or bright light
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
5-The cathode ray is attracted by the plate bearing +ve charges and
repelled by the plate bearing –ve charges so it must consists of
negatively charged particles called electrons
A cathode-ray tube: the fast-moving electrons excite the gas in the
tube, causing a glow between the electrodes(see fig.)
Millikan’s Experiment :Mass of Electron
1. Measured rate of droplet’s fall without voltage: obtained droplet’s
mass.
2. Voltage across plates influenced speed, due to charge on droplet.
3. Quantitative effect of voltage w/ laws of physics -> amt. of charge on
droplet.
4. RESULT: Different droplets had different charge, but always a
multiple of same number ->
elementary charge on electron:
e = 1.602x10-19 coulombs (negative).
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
5- e/m (charge/mass)= - 1.76x108 c/g (Thomson experiments)
5. (Mass/charge) x e- = mass of e-
Rutherford's Experiment On α -Particle Bombardment
of Metal foil :
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Rutherford’s Interpretation— The Nuclear Model
The atom contains a tiny dense center called the nucleus.
– The amount of space taken by the nucleus is only about 1/10
trillionth the volume of the atom.
Prof.H.A.Mohammed
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General Chemistry – Chem 101
Prof.H.A.Mohammed
2.
General Chemistry – Chem 101
The nucleus has essentially the entire mass of the atom.
– The electrons weigh so little they contribute practically no
mass to the atom.
3.
The nucleus is positively charged.
• The amount of positive charge balances the negative charge
of the electrons.
4.The electrons are dispersed in the empty space of
the atom surrounding the nucleus.
• Like water droplets in a cloud.
Some Problems:
• How could beryllium have 4 protons stuck together in the nucleus?
• Shouldn’t they repel each other?
• If a beryllium atom has 4 protons, then it should weigh 4 amu, but
it actually weighs 9.01 amu! Where is the extra mass coming
from?
• Each proton weighs 1 amu.
• Remember: The electron’s mass is only about 0.00055 amu
and Be has only 4 electrons—it can’t account for the extra 5
amu of mass.
• There Must Be Something Else
ThereTo answer these questions, Rutherford proposed that there
was another particle in the nucleus—it is called a neutron.
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General Chemistry – Chem 101
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General Chemistry – Chem 101
• Neutrons (are discovered by Schadwick upon bombarding a thin
sheet of Be with α –particles : high energy radiation was emitted:
neutrons)
have no charge and a mass of 1 amu.
– The masses of the proton and neutron are both
– approximately 1 amu.
Mass and Charge of subatomic particles
Subatomic
Mass
Mass
Location
particle
g
amu
in atom
Proton
1.67262
1.0073
nucleus
Charge
Symbol
1+
p, p+, H+
x 10-24
Electron
empty
space
e, e• The
Modern0.00091
Atom we0.00055
know atoms
are composed
of three main
1−
x 10-24
pieces—protons,
neutrons, and electrons.
0
Neutron
1.67493
1.0087
nucleus
0
n, n
-24
10
• The nucleus xcontains
protons and neutrons.
• The nucleus is only about 10-13 cm in diameter.
P
P
• The electrons move outside the nucleus with an average distance of
about 10-8 cm.
P
P
– Therefore, the radius of the atom is about 105 times larger
than the radius of the nucleus.
P
P
Some Notes on Charges
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General Chemistry – Chem 101
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General Chemistry – Chem 101
– There are two kinds of charges, called positive and negative.
– Opposite charges attract : + attracted to –.
Like charges repel : (+) repels( +)
(–) repels( –).
To be neutral, something
must have no charge or equal
amounts of opposite charges
– Elements:
– Each element has a unique number of protons in its nucleus.
– All carbon atoms have 6 protons in their nuclei.
– The number of protons in the nucleus of an atom is called the
atomic number.
– Z is the short-hand designation for the atomic number.
– Because each element’s atoms have a unique number of
protons, each element can be identified by its atomic number.
– The elements are arranged on the Periodic Table in order of
their atomic numbers.
– Each element has a unique name and symbol.
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General Chemistry – Chem 101
– The symbol is either one or two letters
One capital letter or one capital letter + one lower case letter
Atomic Definitions
A
Z
X
The Nuclear Symbol of the Atom, or Isotope
X = Atomic symbol of the element, or element symbol
A = The Mass number; A = Z + N
Z = The Atomic Number, the Number of Protons in the
Nucleus
(All atoms of the same element have
the same no. of protons.)
N = The Number of Neutrons in the Nucleus
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General Chemistry – Chem 101
Periodic law : Mendeleev
– Ordered elements by atomic mass.
– Saw a repeating pattern of properties.
– Periodic law —When the elements are arranged in order of
increasing relative mass, certain sets of properties recur
periodically?
– Used pattern to predict properties of undiscovered elements.
– Where atomic mass order did not fit other properties, he reordered
by other properties.
Te & I
Periodicity
= Metal
= Metalloid
= Nonmetal
٥۰
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General Chemistry – Chem 101
The Modern Periodic Table
– Elements with similar chemical and physical properties are in the
same column.
– Columns are called Groups or Families.
– Designated by a number and letter at top.
– Rows are called Periods.
– Each period shows the pattern of properties repeated in the next
period.
– Main group = representative elements = “A” groups.
– Transition elements = “B” groups.
– All metals.
– Bottom rows = inner transition elements = rare earth elements.
– Metals
– Really belong in periods 6 and 7.
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General Chemistry – Chem 101
= Alkali metals
= Halogens
= Alkali earth metals
= Lanthanides
= Noble gases
= Actinides
= Transition metals
٥۳
Important Groups—Hydrogen
• Nonmetal.
• Colorless, diatomic gas.
– Very low melting point and density.
• Reacts with nonmetals to form molecular compounds.
– HCl is an acidic gas.
– H 2 O is a liquid.
• Reacts with metals to form hydrides.
– Metal hydrides react with water to form H 2 .
hydrogen halides dissolve in water to form acids
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General Chemistry – Chem 101
Atom Happiness:
• The number of electrons determines the physical and chemical
properties of an atom
• When the protons=electrons atoms are electrically neutral
• But Atom Happiness only comes about when the atom has the
same number of Electrons as a noble gas
• Atoms will not gain and loose protons because protons are at the
center of atoms, very far away from outside, in an electrical shroud
of negative charge
• Atoms will gain and loose electrons, which are on the outside
surface of atoms
• When an atom gains or looses an electron the electrical balance is
lost
• But, atoms are happier with a charge
Ions:
– Ions with a positive charge are called cations.
– More protons than electrons.
– Form by losing electrons.
– Ions with a negative charge are called anions.
– More electrons than protons.
– Form by gaining electrons.
– Chemically, ions are much different than the neutral atoms.
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General Chemistry – Chem 101
– Because they have a different structure.
Atomic Structures of Ions
• Nonmetals form anions.
• For each negative charge, the ion has 1 more electron than the
neutral atom.
o F = 9 p+ and 9 e− ; F─ = 9 p+ and 10 e−.
o P = 15 p+ and 15 e− ; P3─ = 15 p+ and 18 e−.
• Anions are named by changing the ending of the name to –ide.
fluorine
F + 1e− → F─
oxygen
O + 2e− → O2─ oxide ion
fluoride ion
• The charge on an anion can often be determined from the group
number on the periodic table.
– Group 7A ⇒ 1−, Group 6A ⇒ 2−.
• Metals form cations.
• For each positive charge the ion has 1 less electron than the neutral
atom.
• Na atom = 11 p+ and 11 e−; Na+ ion = 11 p+ and 10 e−.
• Ca atom = 20 p+ and 20 e−; Ca2+ ion = 20 p+ and 18 e−.
• Cations are named the same as the metal.
sodium
Prof.H.A.Mohammed
Na → Na+ + 1e−
43
sodium ion
General Chemistry – Chem 101
Prof.H.A.Mohammed
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calcium
Ca → Ca2+ + 2e−
calcium ion
• The charge on a cation can often be determined from the group
number on the periodic table.
 Group 1A ⇒ 1+, Group 2A ⇒ 2+, (Al, Ga, In) ⇒ 3+.
Valence Electrons and Ion Charge
• The highest energy electrons in an atom are called the valence
electrons.
• Metals form cations by losing their valence electrons to get the
same number of electrons as the previous noble gas.
• Main group metals.
• Li+ = 2 e− = He; Al3+ = 10 e− = Ne.
• Nonmetals form anions by gaining electrons to have the same
number of electrons as the next noble gas.
• Cl− = 18 e− = Ar; Se2− = 36 e− = Kr.
Ion Charge and the Periodic Table
• The charge on an ion can often be determined from an elements
position on the periodic table.
• Metals are always positive ions, nonmetals are negative ions.
• For many main group metals, the cation charge = the group
number.
• For nonmetals, the anion charge = the group number – 8.
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General Chemistry – Chem 101
1A
2A
3A
Li+ Be2+
5A 6A 7A
N3− O2− F−
Na+ Mg2+
Al3+
P3− S2− Cl−
2+
K+ Ca
Ga3+
As3− Se2− Br−
Rb+ Sr2+
In3+
Te2− I−
Cs+ Ba2+
٦۲
Structure of the Nucleus
• Soddy discovered that the same element could have atoms with
different masses, which he called isotopes.
– There are two isotopes of chlorine found in nature, one that
has a mass of about 35 amu and another that weighs about 37
amu.
• The observed mass is a weighted average of the weights of all the
naturally occurring atoms.
– The atomic mass of chlorine is 35.45 amu.
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General Chemistry – Chem 101
Isotopes
• All isotopes of an element are chemically identical.
– Undergo the exact same chemical reactions.
• All isotopes of an element have the same number of protons.
• Isotopes of an element have different masses.
• Isotopes of an element have different numbers of neutrons.
• Isotopes are identified by their mass numbers.
– Protons + neutrons.
Neon:
Order of Elements in a Formula
• Metals are written first.
• NaCl
• Nonmetals are written in order from Table 5.1.
• CO 2
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General Chemistry – Chem 101
• There are occasional exceptions for historical or
informational reasons.
• H 2 O, but NaOH .
Ionic Compounds
• Metals + nonmetals.
• No individual molecule units, instead have a 3-dimensional array
of cations and anions made of formula units. Ionic compounds are
made of ions called cations and anions.
• Cations = + charged ions; anions = − charged ions.
• The sum of the + charges of the cations must equal the sum of the
− charges of the anions.
• If Na+ is combined with S2-, you will need 2 Na+ ions for every S2ion to balance the charges, therefore the formula must be Na 2 S.
•
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General Chemistry – Chem 101
Prof.H.A.Mohammed
Prof.H.A.Mohammed
General Chemistry – Chem 101
48
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General Chemistry – Chem 101
Naming Binary Compounds (Type I; Ionic)
• The cation is always named first and the anion
second.
• A monatomic cation takes its name from the
name of the element, e.g. Na+ is called sodium in
the names of compounds containing this ion.
• A monatomic anion is named by taking the first
part of the element and adding –ide, e.g. Cl- is
chloride.
Naming Binary Compounds (Type I; Ionic)
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General Chemistry – Chem 101
Naming Binary Compounds
(Type II; Ionic)
• Applies to cations that can take on
alternate charge states
• Using the principle of charge balance
determine the cation charge.
• Include in the cation name a Roman
numeral indicating the charge.
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General Chemistry – Chem 101
Type II
Tro's "Introductory Chemistry", Chapter
4
Ionic Compounds with Polyatomic
Ions
• Polyatomic ions are assigned special names
that must be memorized.
• Special rules apply to anions that contain
an atom of a given element and different
numbers of oxygen atoms. These anions are
called oxyanions.
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General Chemistry – Chem 101
Prof.H.A.Mohammed
General Chemistry – Chem 101
Tro's "Introductory Chemistry", Chapter
4
Start learning these boldface ones.
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General Chemistry – Chem 101
Rules for Families of Oxoanions
Families with Two Oxoanions
The ion with more O atoms takes the nonmetal root and the
suffix “-ate”.
The ion with fewer O atoms takes the nonmetal root and the
suffix “-ite”.
Families with Four Oxoanions (usually a Halogen)
The ion with most O atoms has the prefix “per-”, the nonmetal
root and the suffix “-ate”.
The ion with one less O atom has just the suffix “-ate”.
The ion with two less O atoms has the just the suffix “-ite”.
The ion with three less O atoms has the prefix “hypo-” and the
suffix “-ite”.
Binary Compounds
(Type III; Covalent – Contain Two Nonmetals:
• The first element in the formula is named first, using the full
element name.
• The second element is named as if it were an anion.
• Prefixes are used to denote the numbers of atoms present.
• The prefix mono- is never used for naming the first element, e.g.
CO is carbon monoxide.
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General Chemistry – Chem 101
NAMING OXOANIONS - EXAMPLES
Prefixes
hypo
Suffixes
Chlorine
Bromine
Iodine
“
”
ate
perchlorate perbromate periodate
[ BrO4-]
[ IO4-]
[ ClO4-]
“
”
ate
chlorate
[ ClO3-]
bromate
[BrO3-]
iodate
[ IO3-]
“
”
ite
chlorite
[ ClO2-]
bromite
[ BrO2-]
iodite
[ IO2-]
“
”
ite
No. of O atoms
per
Root
hypochlorite hypobromite hypoiodite
[ ClO -]
[ BrO -]
[ IO -]
Tro's "Introductory Chemistry", Chapter
4
Binary Compounds
(Type III; Covalent – Contain Two Nonmetals
• The first element in the formula is named first, using the full
element name.
• The second element is named as if it were an anion.
• Prefixes are used to denote the numbers of atoms present.
The prefix mono- is never used for naming the first element, e.g. CO is
carbon monoxide
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General Chemistry – Chem 101
Binary Molecular Compounds
of Two Nonmetals
1. Name first element in formula first.
–
Use the full name of the element.
2. Name the second element in the formula with an
−ide, as if it were an anion.
–
However, remember these compounds do not contain
ions!
3. Use a prefix in front of each name to indicate the
number of atoms.
–
Never use the prefix mono- on the first element.
Tro's "Introductory Chemistry", Chapter
4
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General Chemistry – Chem 101
Subscript—Prefixes
• 1 = mono– Not used on first nonmetal.
• 2 = di• 3 = tri• 4 = tetra• 5 = penta• 6 = hexa• 7 = hepta• 8 = octaDrop last “a” if name begins with vowel
Example—Naming Binary Molecular, BF 3 , Continued
R
R
4. Name the first element.
boron.
4. Name the second element with an –ide.
Fluorine ⇒ fluoride.
4. Add a prefix to each name to indicate the subscript.
monoboron, trifluoride.
4. Write the first element with prefix, then the second element with
prefix.
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Prof.H.A.Mohammed
General Chemistry – Chem 101
– Drop prefix mono- from first element.
boron trifluoride.
Formula-to-Name Acids
• Acids are molecular compounds that often behave like they are
made of ions.
• All names have acid at end.
• Binary Acids = Hydro- prefix + stem of the name of the nonmetal
+ -ic suffix.
• Oxyacids:
– If polyatomic ion ends in –ate = Name of polyatomic ion
with –ic suffix.
– If polyatomic ion ends in –ite = Name of polyatomic ion with
–ous suffix.
Naming Oxyacids:
• If polyatomic ion name ends in –ate, then change ending to –ic
suffix.
• If polyatomic ion name ends in –ite, then change ending to –ous
suffix.
Write word acid at end of all names
Example—Naming Oxyacids, H 2 SO 4 ,Continued
R
R
R
R
4. Identify the anion.
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Prof.H.A.Mohammed
General Chemistry – Chem 101
SO 4 = SO 4 2- = sulfate.
4. If the anion has –ate suffix, change it to –ic. If the anion has –ite
suffix, change it to –ous.
SO 4 2- = sulfate ⇒ sulfuric.
4. Write the name of the anion followed by the word acid.
sulfuric acid
(This is kind of an exception, to make it sound nicer!)
Writing Formulas for Acids
• When name ends in acid, formulas starts with H.
• Write formulas as if ionic, even though it is molecular.
• Hydro- prefix means it is binary acid, no prefix means it is an
oxyacid.
• For an oxyacid, if ending is –ic, polyatomic ion ends in –ate; if
ending is –ous, polyatomic ion ends in –ous.
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