SURVEY OF CHEMISTRY I CHEM 1151 CHAPTER 3

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SURVEY OF CHEMISTRY I CHEM 1151CHAPTER 3
DR. AUGUSTINE OFORI AGYEMAN Assistant professor
of chemistry Department of natural
sciences Clayton state university
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CHAPTER 3 ATOMIC STRUCTURE AND THE PERIODIC
TABLE
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THE ATOMIC THEORY OF MATTER
Daltons Atomic Theory 1. All matter (every
element) is made up of very small particles
called atoms - Atoms are indivisible and
indestructible 2. All atoms of a given element
are identical in mass and properties -
Atoms of a given element are different from atoms
of all other elements
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THE ATOMIC THEORY OF MATTER
Daltons Atomic Theory 3. A chemical reaction is
a rearrangement of atoms - Atoms are neither
created nor destroyed in a chemical reaction 4.
Compounds are formed from a combination of two or
more different kinds of atoms - A given
compound always has the same relative number and
kind of atoms
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THE ATOMIC THEORY OF MATTER
Modern atomic theory is more involved but based
on Daltons theory - Atoms can be destroyed by
nuclear reactions but not by chemical
reactions - There are different kinds of atoms
within an element (isotopes - different
masses, same properties)
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THE ATOMIC THEORY OF MATTER
Law of Constant Composition - The relative
numbers and kinds of atoms are constant in a
given compound - All samples of a given chemical
compound have the same elemental
composition Law of Conservation of Mass
(Matter) The total mass of materials after a
chemical reaction is equal to the total mass
before the chemical reaction
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THE ATOMIC THEORY OF MATTER

• Law of Multiple Proportions
• When two or more elements combine to form a
  compound, their masses in that
• compound are in a fixed and definite ratio
• Elements combine in a ratio of small whole
  numbers
• - If two elements form more than one compound,
  the ratios of the masses of the
• second element combined with a fixed mass of
  the first element will be in ratios
• of small whole numbers

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THE ATOMIC STRUCTURE
Atom - Is the smallest particle of an element
that retains the chemical identity of the
element - Is the basic building block of ordinary
matter - Made up of smaller particles (the
building blocks of an atom) called subatomic
particles Three Types of Subatomic
Particles Electron possesses a negative (-)
electrical charge Proton possesses a positive
() electrical charge Neutron has no charge (it
is neutral)
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THE ATOMIC STRUCTURE
Electronic Charge equals 1.602 x 10-19 C (C
coulombs) - Charges are usually expressed as
multiples of the electronic charge Charge of an
electron -1.602 x 10-19 C -1 Charge of a
proton 1.602 x 10-19 C 1 Atoms have no net
electrical charge since they have equal number
of electrons and protons
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THE ATOMIC STRUCTURE
- Protons and neutrons have very large masses
(about 2000 x) as compared to electrons - Atoms
generally have extremely small masses - Atomic
Mass Unit (amu) is used to express such small
masses 1 amu 1.66054 x 10-24 g or 1 g
6.02212 x 1023 amu
Mass (amu) 1.0073 1.0087 5.486 x 10-4
Relative Mass 1837 1839 1
Charge Positive (1) Neutral (0) Negative (-1)
Particle Proton Neutron Electron
Mass (g) 1.673 x 10-24 1.675 x 10-24 9.109 x
10-28
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THE ATOMIC STRUCTURE
- The center of an atom is small, dense, and
positively charged called the nucleus - The
nucleus contains all protons and neutrons and are
referred to as necleons - The nucleus is,
therefore, positively charged and contributes
about 99.9 of the mass of an atom
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THE ATOMIC STRUCTURE

• - The electrons move rapidly around the nucleus
• - Outer region called the extranuclear region
• - Account for most of the volume of an atom
• Electron Cloud
• - Volume occupied by electrons
• - Negatively charged

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ATOMIC NUMBER
Atomic Number (Z) The number of protons in the
nucleus of an atom Since atoms have no net
electrical charge number of protons number of
electrons Z number of protons number of
electrons
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MASS NUMBER

• Mass Number (A)
• - The sum of the number of protons and
• the number of neutrons in the nucleus of an atom
• The total number of subatomic particles in the
  nucleus of an atom
• - The number of nucleons of an atom
• A number of protons number of neutrons
• number of neutrons mass number - atomic number
  A - Z

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ATOMIC AND MASS NUMBERS
MASS NUMBER
CHEMICAL SYMBOL
ATOMIC NUMBER
A
SYMBOL
Z
16
40
12
O
Ca
C
20
8
6
Mass number is the superscript to the left Atomic
number is the subscript to the left
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ATOMIC AND MASS NUMBERS
An atom has an atomic number of 56 and a mass
number of 138. What are the numbers of protons,
electrons, and neutrons present in the atom? What
is the number of subatomic particles present in
the nucleus of the atom? Number of protons
atomic number 56 Number of electrons atomic
number 56 Number of neutrons mass number
atomic number 138-56 82 Number of subatomic
particles in the nucleus mass number 138
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CHEMICAL PROPERTIES OF ATOMS
- The number of protons (the atomic number)
characterizes an atom - Electrons determine the
chemical properties of an atom - Atoms with the
same atomic number have the same chemical
properties - Atoms with the same atomic number
are atoms of the same element
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CHEMICAL PROPERTIES OF ATOMS
An Element - Is a pure substance that cannot be
reduced to a simpler substance by normal chemical
means (from chapter 1) An Element - Is a pure
substance in which all atoms present have the
same atomic number (chapter 2)
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ISOTOPES
- Atoms of an element with the same atomic number
but different mass numbers - Atoms of an
element with the same number of protons and the
same number of electrons but different numbers
of neutrons - Isotopes of an element have the
same chemical properties but slightly different
physical properties - The atomic number is
usually omitted since it is the same for
isotopes of a given element
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ISOTOPES
11
12
13
14
C
C
C
C
Most abundant is carbon-12
6
6
6
6
1
2
3
H
H
H
Most abundant is hydrogen-1
1
1
1
28
29
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Si
Si
Si
Most abundant is silicon-28
14
14
14
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ATOMIC MASS
1 amu 1.66054 x 10-24 g or 1 g 6.02214 x 1023
amu amu atomic mass unit amu is defined by
assigning a mass of exactly 12 amu to an atom of
carbin-12 (reference point) Average Atomic Mass
- Determined by using the masses of an elements
various isotopes and their respective relative
abundances The average atomic mass of an element
(in amu) is the elements atomic weight
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ATOMIC MASS
For an element with n isotopes, which have atomic
masses or relative masses in amu (m1, m2,
m3,.., mn) and relative abundances expressed as
fractions (x1, x2, x3,,xn) Average Atomic
Mass m1x1 m2x2 m3x3 . mnxn
The relative abundance is usually expressed as a
percentage Divide by 100 to convert to the
decimal form (fractional abundance)
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ATOMIC MASS
Naturally occurring copper is 69.09 63Cu, which
has a relative mass of 62.93 amu, and 30.91
65Cu, which has a relative mass of 64.93 amu.
Calculate the average atomic mass of copper.
63Cu relative abundance 69.09
fractional abundance 69.09/100 0.6909
65Cu relative abundance 30.91
fractional abundance 30.91/100 0.3091
Average Atomic Mass (62.93)(0.6909)
(64.93)(0.3091) 63.5478
63.55 amu
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PERIODIC TABLE OF ELEMENTS
- 116 known elements - 91 naturally occurring
elements - 25 are found in nature but made in the
laboratory Periodic Table - Elements are
arranged in a tabular form (called the periodic
table) in order of increasing atomic number such
that elements with similar chemical properties
are positioned in vertical columns - A tool that
chemists use for organizing and remembering
chemical facts
Atomic number
SYMBOL
Atomic mass
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PERIODIC TABLE OF ELEMENTS
Period - The horizontal row of elements in the
periodic table - Labeled with Arabic numbers from
top to bottom - First row is period 1, second
row is period 2, etc Group - The vertical
column of elements in the periodic table - May
be labeled with Arabic numbers (1 through 18)
or Roman numerals with letters A and B
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PERIODIC TABLE OF ELEMENTS
Groups With Special Names Alkali Metals -
Elements in Group IA (excluding hydrogen) Li, Na,
K, Rb, Cs, and Fr - Properties soft, shiny,
react readily with water Alkaline Earth
Metals - Elements in Group IIA Be, Mg, Ca, Sr,
Ba, Ra - Properties soft, shiny, react
moderately with water
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PERIODIC TABLE OF ELEMENTS
Groups With Special Names Chalcogens - Elements
in Group VIA O, S, Se, Te, Po - Properties
commonly found as minerals Halogens - Elements
in Group VIIA F, Cl, Br, I, At - Properties
reactive, colored, gas at room temperature
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PERIODIC TABLE OF ELEMENTS
Groups With Special Names Noble Gases -
Elements in Group VIIIA He, Ne, Ar, Kr, Xe, Rn -
Properties unreactive gases
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PERIODIC TABLE OF ELEMENTS
Classification by Physical Properties Metals -
Elements on the left block of the periodic
table Characteristics - good conductors of
heat and electricity - ductile (capable of being
shaped or drawn into wire) - malleable (capable
of being rolled into sheets) - high luster
(shiny) - high melting points - high density -
solids at room temperature (except
mercury) (iron, aluminum, gold, silver, copper)
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PERIODIC TABLE OF ELEMENTS
Classification by Physical Properties Nonmetals -
Elements on the right block of the periodic
table Characteristics - poor conductors of
heat and electricity - good insulators (except
diamond) - no metallic luster - nonductile -
lower melting points - lower density - solids,
liquids or gases at room temperature (oxygen,
hydrogen, nitrogen, carbon, sulfur, bromine)
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PERIODIC TABLE OF ELEMENTS
Classification by Physical Properties Metals and
nonmetals on the periodic table are separated by
a bold steplike line running from Group IIIA
through Group VIA Metalloids - Some elements
that lie along the line separating metals from
nonmetals Characteristics - Properties fall
between those of metals and nonmetals (Si, Ge,
As, Sb, Te, Po, At)
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ELECTROMAGNETIC RADIATION
- Also known as radiant heat or radiant energy -
One of the ways by which energy travels through
space Examples heat energy in microwaves,
light from the sun, X-ray, radio waves The
properties of light is a key concept that helps
in understanding electronic structure
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ELECTROMAGNETIC RADIATION
Three Characteristics of Waves Wavelength (?) -
Distance between two consecutive peaks or troughs
in a wave Frequency (?) - The number of waves
(cycles) per second that pass a given point in
space Speed - All waves travel at the speed of
light in vacuum (3.00 x 108 m/s)
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ELECTROMAGNETIC RADIATION
?1
amplitude
?1 4 cycles/second
?2
?2 8 cycles/second
peak
?3
?3 16 cycles/second
trough
one second
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ELECTROMAGNETIC RADIATION
Wavelength (m)
10-11
103
Radio frequency FM Shortwave AM
Gamma rays
Ultr- violet
Infrared
Microwaves
Visible
X rays
Frequency (s-1)
104
1020
Visible Light VIBGYOR Violet, Indigo, Blue,
Green, Yellow, Orange, Red 400 750 nm - White
light is a blend of all visible wavelengths -
Can be separated using a prism
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ELECTROMAGNETIC RADIATION
- Inverse relationship between wavelength and
frequency ? a 1/? c ? ? ? wavelength
(m) ? frequency (cycles/second 1/s s-1
hertz Hz) c speed of light (3.00 x 108 m/s)
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ELECTROMAGNETIC RADIATION
An FM radio station broadcasts at 90.1 MHz.
Calculate the wavelength of the corresponding
radio waves c ? ? ? ? ? 90.1 MHz 90.1
x 106 Hz 9.01 x 107 Hz c 3.00 x 108 m/s ?
c/ ? 3.00 x 108 m/s/9.01 x 107 Hz 3.33 m
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ARRANGEMENT OF ELECTRONS
The space around a nucleus in which electrons
move are divided into - Shells -
Subshells - Orbitals
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ARRANGEMENT OF ELECTRONS
Electron Shells - Numbered from the nucleus
outward using 1, 2, 3, n - Electron energy
increases with distance from the nucleus - An
electron in shell 2 has higher energy than an
electron in shell 1 - An electron in shell 3 has
higher energy than an electron in shell 2
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ARRANGEMENT OF ELECTRONS
Electron Shells - The higher the shell number,
the more electrons the shell can contain - The
maximum number of electrons a shell can
accommodate is given by 2n2, where n is the
shell number - The first shell (n 1)
accommodates 2 electrons maximum - The second
shell (n 2) accommodates 8 electrons maximum -
The third shell (n 3) accommodates 18 electrons
maximum
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ARRANGEMENT OF ELECTRONS
Electron Subshells - Each electron shell is
subdivided into subshells containing electrons
that have the same energy - The shell number
indicates the number of subshells - Shell 1
contains 1 subshell - Shell 2 contains 2
subshells - Shell 3 contains 3 subshells Subshell
s differ in size and energy
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ARRANGEMENT OF ELECTRONS
Electron Subshells - The higher the energy of
electrons in a given subshell the larger the
subshell Subshells are designated in the order
of increasing size and energy as s, p, d, f
Subshell s p d f
Maximum Number of Electrons 2 6 10 14
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ARRANGEMENT OF ELECTRONS
Electron Subshells s sharp (spherical) p
principal (peripheral) d diffuse f
fundamental
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ARRANGEMENT OF ELECTRONS
Electron Subshells - Identified by the shell
number and the subshell letter (type)
Shell 1
1 subshell
1s
2 electrons
2p 2s
6 electrons 2 electrons
Shell 2
2 subshell
10 electrons 6 electrons 2 electrons
3d 3p 3s
3 subshell
Shell 3
14 electrons 10 electrons 6 electrons 2
electrons
4f 4d 4p 4s
4 subshell
Shell 4
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ARRANGEMENT OF ELECTRONS
Electron Orbitals - An orbital is a region of
space within an electron subshell - The
electron with a specific energy has a high
probability of being found - An orbital can
accommodate a maximum of 2 electrons s subshell
(2 electrons) contains 1 orbital p subshell (6
electrons) contains 3 orbitals d subshell (10
electrons) contains 5 orbitals f subshell (14
electrons) contains 7 orbitals
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ARRANGEMENT OF ELECTRONS
Electron Orbitals s orbital is spherical p
orbital looks like 8 (2 lobes) d orbital is
similar to two intercrossing 8 (4 lobes) f
orbital is more complex (8 lobes or something
similar)
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ELECTRON CONFIGURATION
- Elements in the periodic table are arranged in
order of increasing atomic number (number of
protons) - Similar to protons, electrons are
added one by one to the nucleus to build up
elements (Aufbau Principle)
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ELECTRON CONFIGURATION
Rules for assigning electrons - Electron
subshells are filled in order of increasing
energy (s, p, d, f) - All orbitals of a
subshell acquire single electrons before any
orbital acquire a second electron (Hunds
rule) - All electrons in singly occupied
orbitals must have the same spin - A maximum of
2 electrons can exist in a given orbital and must
have opposite spins (Pauli principle)
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ELECTRON CONFIGURATION
- Ordering of electron subshells is often
complicated due to overlaps For instance, the 3d
subshell has higher energy than the 4s subshell -
Use of mnemonic for subshell filling is essential
1s
The (n1) orbitals always fill before the nd
orbitals
2s
2p
3s
3p
3d
4s
4p
4d
4f
5s
5p
5d
5f
6s
6p
6d
7s
7p
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ELECTRON CONFIGURATION
- Subshells containing electrons are designated
using the sunshell numbers and letters (types)
- The number of electrons in a given subshell
is indicated by a superscript Carbon has 6
electrons 1s22s22p2 Nitrogen has 7 electrons
1s22s22p3 Sodium has 11 electrons 1s22s22p63s1
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ORBITAL DIAGRAMS
Hydrogen has electronic configuration written as
1s1 The orbital diagram is
1s
H
Helium has electronic configuration written as
1s2 The orbital diagram is
1s
He
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ORBITAL DIAGRAMS
Lithium has electronic configuration written as
1s22s1 The orbital diagram is
1s
2s
Li
Beryllium has electronic configuration written as
1s22s2 The orbital diagram is
2s
1s
Be
Boron has electronic configuration written as
1s22s22p1 The orbital diagram is
2p
2s
1s
B
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ORBITAL DIAGRAMS
Carbon has electronic configuration written as
1s22s22p2 The orbital diagram is
1s
2p
2s
C
Nitrogen has electronic configuration written as
1s22s22p3 The orbital diagram is
2s
1s
2p
N
Sodium has electronic configuration written as
1s22s22p63s1 The orbital diagram is
2p
2s
3s
1s
Na
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CLASSIFICATION OF THE ELEMENTS
- Elements in a given group have similar chemical
properties because the outer-shell electron
arrangements are similar Group IIA elements Be
1s22s2 Mg 1s22s22p63s2 Ca 1s22s22p63s23p64s2 Sr
1s22s22p63s23p64s23d104p65s2
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CLASSIFICATION OF THE ELEMENTS
- The last electron in an elements electron
configuration causes the difference in the
electron configuration of the preceding element
and is referred to as the distinguishing
electron
Homework Write notes (one page) on the different
classifications of the elements based on
electronic properties. Briefly describe the
s-area, p-area, d-area, and the f-area.
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CLASSIFICATION OF THE ELEMENTS

• Elements can be classified as
• Metals or Nonmetals
• Based on physical properties
• Elements can also be classified as
• Noble-gas, Representative,
• Transition, or Inner Transition
• - Based on electron configuration

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CLASSIFICATION OF THE ELEMENTS
Noble-gas Elements - Group VIIIA (18) elements
on the periodic table (far right column) -
Gases at room temperature - Little tendency to
form chemical compounds - Electron configuration
ends in p6 - Completes p subshell (except
Helium) - Nonmetals
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CLASSIFICATION OF THE ELEMENTS
Representative Elements - Elements in the
s-area (Groups IA and IIA) first five columns
of the p-area (Groups IIIA, IVA, VA, VIA, and
VIIA) - Metals and nonmetals
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CLASSIFICATION OF THE ELEMENTS
Transition Elements - Elements in the d-area of
the periodic table - Groups IIIB (3), IVB (4),
VB (5), VIB (6), VIIB (7), VIIIB (8, 9, 10), IB
(11), and IIB (12) - Distinguishing electron in
a d subshell - Metals
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CLASSIFICATION OF THE ELEMENTS
Inner Transition Elements - Elements in the
f-area of the periodic table - The two-row block
of elements below the main table -
Distinguishing electron in an f subshell -
Metals