1
INTERNATIONAL UNVERSITY
FOR SCIENCE & TECHNOLOGY
Atoms, Molecules, and Ions
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
2
INTERNATIONAL UNVERSITY
FOR SCIENCE & TECHNOLOGY
‫قوانين االتحادات الكيميائية‬
The Combination Laws in Chemistry
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
3
The Conservation Law of Mass
‫قانون مصونية المادة‬
(Lavoiseir’s Law ‫(قانون الفوازييه‬
‫ ومجموع كتل المواد يبقى دون أي تغيير‬,‫المادة مصانة في التفاعل الكيميائي‬
)‫(المادة التفنى والتخلق وإنما هناك تحول من شكل إلى آخر‬. ‫خالل التفاعل‬
-The mass is conserved during the chemical reaction, and
the total masses remain unchanged.
‫ مجموع كتل المواد الداخلة في التفاعل يساوي مجموع كتل المواد الناتجة‬. ‫عن التفاعل‬
-The sum of reactant masses is equal to the sum of
product masses.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
4
The Conservation Law in
Chemistry
Lavoiseir’s Law
:‫قانون مصونية المادة بعد دالتون‬
‫ فإننا نستطيع ان نكتب قانون‬, ‫حيث ان التفاعل الكيميائي يحدث بين الذرات‬
:‫انحفاظ المادة بالشكل التالي‬
‫ مجموع عدد الذرات الداخلة في التفاعل يساوي مجموع عدد الذرات الناتجة‬. ‫عن التفاعل‬
The Conservation Law After Dalton's theory
Since the chemical reaction happens between the atoms,
we can write Lavoisier's law as:
The sum of reactant atoms is equal to the sum of
product atoms.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
5
The Conservation Law in
Chemistry
Lavoiseir’s Law
: ‫قانون انحفاظ المادة على ضوء نظرية اينشتاين‬
:‫ نستطيع أن نكتب قانون انحفاظ المادة بالشكل التالي‬, ‫بعد ظهور نظرية اينشتاين‬
‫مجموع كتل المواد الداخلة في التفاعل يساوي مجموع كتل المواد الناتجة عن‬
‫ آخذين بعين اإلعتبار تحول المادة إلى طاقة ( التفاعالت الناشرة‬, ‫التفاعل‬
) ‫للحرارة) وتحول الطاقة إلى مادة (في التفاعالت الماصة للحرارة‬
After the relativity theory of Einstein:
we can write the conservation law as the following:
The sum of reactant masses is equal to the sum of
product masses taking in consideration, the
transformation of heat to mass and vies versa
(according to Einstein equation E=mc²).
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
‫‪6‬‬
‫قانون النسب الثابتة (‪(Definite Proportions Law‬‬
‫قانون بروست )‪(Proust's Law‬‬
‫قانون النسب الثابتة ‪The definite proportions law‬‬
‫إذا اتحد عنصران معا لتشكيل مركب ما ‪ ,‬فإن اتحادهما يتم وفق نسبة وزنية‬
‫ثابتة ‪.‬‬
‫فالهيدروجين يتحد مع األوكسجين لتشكيل الماء‪ ,‬حيث يتحد ‪2‬غرام من‬
‫الهيدروجين مع ‪ 16‬غرام من األوكسجين ‪ ,‬والنسبة ‪ 16\2‬هي نسبة‬
‫وزنية ثابتة‪.‬‬
‫‪H₂ + O → H₂O‬‬
‫‪2g‬‬
‫‪16g‬‬
‫)‪2g/16g (definite ratio‬‬
‫أو يمكن القول بصورة عامة ‪:‬‬
‫في أي مركب ‪ :‬هناك نسبة وزنية ثابتة بين العناصر المشكلة لهذا المركب‬
‫مهما كانت طريقة الحصول عليه‬
‫‪Chapter Two‬‬
‫‪.‬‬
‫‪General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry‬‬
‫‪Prentice Hall © 2005‬‬
7
(Definite Proportions Law( ‫قانون النسب الثابتة‬
(Proust's Law) ‫قانون بروست‬
The definite proportions law ‫قانون النسب الثابتة‬
If tow elements combine to form a compound, their
combination will occur according to a fixed ratio of
masses , hydrogen combines with oxygen to form
water with a mass ratio 2grams/16grams
H₂ + O → H₂O
2g
16g
2g/16g (definite ratio)
in other wards:
In any compound there is a fixed ratio of masses between
the elements in this compound.
Example:
In H₂SO₄ compound 2/32/64 is a fixed mass ratio.
Prentice Hall
. © 2005
Chapter Two
General Chemistry 4 edition, Hill, Petrucci, McCreary, Perry
th
8
Proust's Law or Definite
Proportions Law
Example(1):
If the carbon combines with oxygen to form the carbon
dioxide compound, this happens always between 12
grams of carbon and 32 grams of oxygen and the ratio
12/32 is a fixed mass ratio.
C + O₂ → CO₂
12
32
12/32 is a fixed ratio.
Example(2):
In H₃PO₄ compound 3/31/64 is a fixed mass ratio.
.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
9
(Definite Proportions Law( ‫قانون النسب الثابتة‬
(Proust's Law) ‫قانون بروست‬
The mass ratio of oxygen to magnesium in the
compound magnesium oxide is 0.6583:1. What mass of
magnesium oxide will form when 2.000 g of magnesium
is completely converted to magnesium oxide by burning
in pure oxygen gas?
2MgO----------------- 2Mg + O2
1
0.6583
?
2
?
AThe mass of oxygen = 2x 0.6583 = 1.3166 g
The mass of magnesium oxide= 2 + 1.3166 = 3.3166 g
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
‫‪10‬‬
‫قانون النسب الثابتة (‪(Definite Proportions Law‬‬
‫قانون بروست )‪(Proust's Law‬‬
‫قانون النسب الثابتة على ضوء نظرية دالتون‪:‬‬
‫حيث أن التفاعل الكيميائي يحدث بين الذرات ‪ ,‬فإنه يمكن القول‪:‬‬
‫في أي مركب هناك نسبة عددية ثابتة بين الذرات المشكلة لهذا المركب ‪.‬‬
‫مثال ‪:‬‬
‫في حمض الكبريت ‪H₂SO₄‬هناك نسبة عددية ثابتة بين العناصر المشكلة له‬
‫‪ ,‬هي ‪2/1/4‬‬
‫‪After Dalton‬‬
‫‪We say: There is a fixed ratio of the atoms in any‬‬
‫‪compound, In H₂SO₄ compound 2/1/4 is a fixed atomic‬‬
‫‪ratio.‬‬
‫‪.‬‬
‫‪Chapter Two‬‬
‫‪General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry‬‬
‫‪Prentice Hall © 2005‬‬
‫‪11‬‬
‫‪Law of Multiple Proportions‬‬
‫)‪ (cont’d‬قانون النسب المضاعفة أو البسيطة‬
‫قانون النسب البسيطة أو المضاعفة ‪Law of Multiple proportions‬‬
‫إذا اتحد عنصران معا ‪ ,‬لتشكيل أكثر من مركب ‪ ,‬فإن نسبة أوزان أحدهما‬
‫الالزمة لالتحاد مع وزن ثابت من العنصر اآلخر هي نسبة بسيطة أو‬
‫مضاعفة‪.‬‬
‫مثال‪:‬يتحد الكربون مع األوكسجين لتشكيل مركبين ‪ ,‬ثنائي أوكسيد الكربون‬
‫‪ CO₂‬وأول اوكسيد الكربون ‪.CO‬‬
‫‪C + O → CO‬‬
‫‪Ratio of oxygen-to-carbon in CO2 is‬‬
‫‪1216‬‬
‫‪exactly twice the ratio in CO.‬‬
‫‪C + O₂ → CO₂‬‬
‫‪12 32‬‬
‫‪the 16/32=1/2 is a simple ratio‬‬
‫‪Chapter Two‬‬
‫‪General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry‬‬
‫‪Prentice Hall © 2005‬‬
12
Law of Multiple Proportions
‫( قانون النسب المضاعفة أو البسيطة‬cont’d)
Law of Multiple Proportions:
If two elements combine to form more than one
compound , the masses of one element that combine with
a fixed mass of the second element are in the ratio of
small whole numbers.
C + O → CO
1216
Ratio of oxygen-to-carbon in CO2 is
C + O₂ → CO₂
exactly twice the ratio in CO.
12 32
the 16/32=1/2 is a simple ratio
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
13
Law of Multiple Proportions
‫قانون النسب المضاعفة أو البسيطة‬
• Four different oxides of nitrogen can be formed by
combining 28 g of nitrogen with:
• 16 g oxygen, forming Compound I
• 48 g oxygen, forming Compound II
• 64 g oxygen, forming Compound III
• 80 g oxygen, forming Compound IV
What is the ratio 16:48:64:80
expressed as small whole numbers?
1:3:4:5
• Compounds I–IV are N2O, N2O3, N2O4, N2O5
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Daltons' Atomic Theory
John Dalton and his Atomic Theory
Introduction:
Dalton was the first to distinguish between
two types of substance:
-Elements
-Compounds
Prentice Hall © 2005
14
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Daltons' Atomic Theory
1-Atom is the smallest unit of the element and cannot be
broken down by ordinary chemical operations
2-All atoms of an element are alike in the physical
and chemical properties.
3-Molecule is smallest unit of the compound and it is
composed of 2 atoms or more.
4-All molecules of the same compound are alike in
physical and chemical properties.
5-Atoms are conserved during the chemical reaction
and the chemical reaction is a new rearrangement of
the atoms to produce new compounds.
Prentice Hall © 2005
15
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms in Chemistry
1-atom:
It s the smallest distinctive unit of element and
cannot be broken down by ordinary chemical
operations.
2-: molecule
It is the smallest distinctive unit of compound and
it is composed of 2 atoms or more.
3-Ion:
It is an atom or a group of atoms having positive or
negative charges.
Prentice Hall © 2005
16
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms in Chemistry
Q-Determine which of the following
represent elements and which do not.
C, CO, Cl, CaCl2, Na, KI
Q-Determine which of the following
represent molecules and which do not.
N , N₂ , No , NO , O , O₂ , O₃ , Os
Prentice Hall © 2005
17
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms in Chemistry
4-Atomic Mass:
It is the mass of the atom given by the atomic
mass unit (u).
5-Atomic Mass Unit ( a.m.u.):
It is 1/12 of the mass of the ¹²₆C atom
6-Molculer Mass:
It is the mass of molecule by the a.m.u. and
equals the sum of all the masses of atoms in
the formula.
Prentice Hall © 2005
18
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms in Chemistry
7- Gram Atomic Mass:
It is the mass of atom in grams, and it is called the
mole.
8- Gram Molecular Mass:
It is the mass of molecule in grams, and it is called
the mole.
9-Mole(Molar Mass):
It is the mass of atom or molecule using gram as
unit and it contains Avogadro's number of atoms
or molecules.
Prentice Hall © 2005
19
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms in Chemistry
10-Avogadro's number:
It is the number of atoms or molecules in
the mole of atoms or molecules, and
equals 6.023x10²³.
11-Avogadro's mole volume:
At the standard conditions of pressure and
temperature, the mole of any gas
occupies a volume of 22.4 lit.
Prentice Hall © 2005
20
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms in Chemistry
Q-Calculate the molecular mass of each of the
following:
Li2O, C3H7Br, (CH3CH2CH2)2O, KHSO3,
N2O5, KNO2
Q-Calculate the number of moles of CO present in a
125 g sample of the gas.
Q-Calculate the number of sodium atoms Na in 4.6 g
of sodium metal?
Q-Calculate the number of ammonium ions in
0.26 g of ammonium sulphate (NH₄)₂SO₄
Prentice Hall © 2005
21
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms in Chemistry
12-Atomic Number(Z):
-It is the number of protons or number of
electrons in neutral atom.
-It is the identity card of the element.
-It is the number of box of the element in the
periodic table.
13-Mass Number(A):
It is the sum of protons and neutrons in the
nucleus.
Prentice Hall © 2005
22
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms
in Chemistry
Isotopes
14-The Isotopes:
Are atoms of the same element with the same
atomic number and different mass number.
-Each element has isotopes, some are stable and
some are radioactive, for example carbon has
three isotopes:
¹³₆C, ¹⁴₆C ¹²₆C,
The isotope ¹⁴₆C , is radioactive.
Prentice Hall © 2005
23
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Atomic
Isotopes
Mass (cont’d)
Question: do all isotopes of an element have
the same mass? Why or why not?
The atomic mass given on the periodic table
is the weighted average of the masses of the
naturally occurring isotopes of that element.
Prentice Hall © 2005
24
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Example 2.4
Use the data cited above to determine the weighted
average atomic mass of carbon.
ATo find the weighted average , we have to multiply the
fractional abundance of each isotope with it’s atomic
mass :
Carbon-12=12x0.98892=11.86704
Carbon-13=13x0.01108=0.1534
The weighted average=12.02044
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
25
Chapter Two
Example:
Which of the following pairs of symbols represent
isotopes?
Example:
Indicate the numbers of protons, neutrons and electrons
in the following atoms:
Prentice Hall © 2005
26
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Keys and Terms in Chemistry
15-Standard conditions of pressure and
temperature:
P=1 atm.= (76 cm/Hg) =(760 mm/Hg)
T=273° deg. ( K°)
At the sea level
Prentice Hall © 2005
27
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Atomic Weights
Average Atomic Masses
• Relative atomic mass: average masses of isotopes:
– Naturally occurring C: 98.892 % 12C + 1.108 % 13C.
• Average mass of C:
• (0.98892)(12 amu) + (0.0108)(13.00335) = 12.011 amu.
• Atomic weight (AW) is also known as average atomic
mass (atomic weight).
• Atomic weights are listed on the periodic table.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Electrons
Electrons:
J. Thompson used vacuum tube ( crocks tube ) with
two electrodes , he applied a high voltage current
between the electrodes about 3000 v and a low
pressure of inert gas about 10ˉ⁵ Torr,he noticed
that a beam of gluing rays comes from the
cathode to the anode , he called it the cathodic
rays.
Thompson found that the cathodic rays are
composed of tiny small particles with a mass and
negative charge, called later electrons.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Radiations
• Hennery Becquerel discovered the radiation activity in elements and
found three types of rays :
• Alfa Rays (α):
• A beam of particles with a mass and positive charge ( He⁺⁺
nuclei ) with high energy and small penetration power.
• Beta Rays (β):
• A beam of particles with a mass and negative charge ( high
speed electrons) with high energy and high penetrating
power.
• Gamma Rays (γ):
• A beam of electromagnetic waves ( light) with very
high energy and very high penetrating power.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
31
Subatomic Particles
• Protons and neutrons are located at the center of
an atom (at the nucleus).
• Electrons are dispersed around the nucleus.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
32
Mendeleev’s Periodic Table
• Mendeleev arranged the known elements in order of
increasing atomic weight from left to right and from top to
bottom in groups.
• Elements that closely resembled one another were arranged
in the same vertical group.
• He found the chemical and physical properties are
weight dependent .
• Gaps were left where undiscovered elements should
appear.
• From the locations of the gaps, he was able to predict
properties of some of the undiscovered elements.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
33
The Modern Periodic Table
Except for H,
elements left of
the zigzag line
are metals.
To the right of
the line we find
nonmetals,
including the
noble gases.
Some elements
adjacent to the
line are called
metalloids.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
34
The Modern Periodic Table
• In the modern periodic table , the known
elements are arranged in order of increasing
atomic numbers from left to right and from top
to bottom in groups.
• Elements in the same vertical group are closely
resembled one another .
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
35
The Modern Periodic Table
• The modern Periodic Table consists of :
• - Seven horizontal lines( rows ) of elements called
Periods.
• - Eight vertical columns called Groups or Families.
• - About 37 transition elements of the type(d), in ten
groups at the middle of table.
• - 28 transition elements of the type (f) , in two series
each with 14 elements : Lanthanide series and Actinide
series are located at bottom of the table.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
36
Main Elements and Transition Elements
• The elements of the periodic table are two types:
• - Main Elements :where the electron fill the outer shell
orbitals of the types s and p .
• The Aqueous solutions of the compounds of the main
elements are colorless .
• - Transition Elements: where the electrons fill inner shell
orbitals of the types d and f .
• The Aqueous solutions of the transition elements
compounds have distinguish colors and form metal
complexes.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
37
Metals , Nonmetals and Metalloids
The Octet Rule in Elements
All Elements tend to have eight electrons in their outer
shell , or the outer shell electron configuration of the
nearest noble gas , either by losing one electron (or more)
or by gaining one electron (or more) , or by sharing
electrons.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
38
Metals , Nonmetals and Metalloids
- Metals :
Are the elements which tend to lose one electron or
more to form positive ions .
Na → Na⁺ + e
Ca → Ca⁺⁺ + 2e
Metals form about 75% of elements.
Metallic properties: increase when we move from right
to left , and from top to the bottom in the periodic table.
Metals have a characteristic luster and generally are
good conductors of heat and electricity , metals are
malleable.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
39
Metals , Nonmetals and Metalloids
-Nonmetals :
Are the elements which tend to gain one electron or
more to form negative ions.
Cl + e → Cl⁻
O + 2e → O⁻⁻
The nonmetallic properties: increase when we move
in the periodic table ,from left to right and from bottom
to the top.
Nonmetals are generally are poor conductors of heat
and electricity , some are gasses and some are brittle
solids.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
40
Metals , Nonmetals and Metalloids
• -Metalloids :
• Are the elements which display the properties of metals
and nonmetals.
• The metalloids located :at the center of the periodic
table , between the metals and nonmetals elements.
• In some groups: we can find metals and nonmetals in the
same column , and the metalloids in between.
Example:
In group 4 , carbon C and silicon Si at the top of the
group , are nonmetals , while tin Sn and lead Pb in the
bottom are metals, germanium Ge in between is a
metalloid.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
41
Ions and Ionic Compounds
The Ion: Is an atom or a group of atoms having
negative or positive charges.
The Positive ions are called: CATIONS
The negative ions are called: ANIONS
Atoms that lose
electrons form cations
Na  Na+ + e–
Atoms that gain
electrons form anions
Cl + e–  Cl–
EOS
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
42
Ions and Ionic Compounds
The Ionic Compounds :
Are the compounds formed by oppositely charged
ions , linked by the electrical attractive forces.
(in the ionic compounds there is no net charge)
Ionic Bond:
It is the bond which is formed by the electrostatic
attraction forces between two oppositely charged
ions.
Binary Ionic Compound:
It is the ionic compound which is composed of two
kinds of atoms.
EOS
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Ions and ionic compounds
Binary Ionic Compounds:
Sodium chloride :NaCl
Potassium Bromide: KBr
Calcium Iodide: CaI₂
Barium Oxide: BaO
Cobalt(lll) fluoride: CoF₃
Sodium sulphide: Na₂S
Aluminum Phosphide: AlP
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Ions and ionic compounds
Polyatos Ionic Compounds:
Polyatoms ionic compound are composed of more
than two kinds of atoms.
Sodium perchlorate :NaClO₄
Potassium chlorate: KClO₃
Calcium sulphate: CaSO₄
Barium Nitrate: Ba(NO₃)₂
Magnesium Nitrite: Mg(NO₂)₂
Sodium sulphite: Na₂SO₃
Potassium Cyanide: KCN
Ammonium Chloride: NH₄Cl
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Molecular compounds
Binary Molecular Compounds:
Binary molecular compounds are composed of two
kinds of nonmetal atoms.
Carbon monoxide :CO
Carbon dioxide: CO₂
Carbon sulphide: CS₂
Nitrogen monoxide: NO
Nitrogen dioxide: NO₂
Dinitrogen trioxide : N₂O₃
Dinitrogen tetra oxide: N₂O₄
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Molecular compounds
Binary Molecular Compounds:
Carbon tetra chloide :CCl₄
sulphur dioxide: SO₂
sulphur tetra fluoride: SF₄
Sulphur hexa fluoride: SF₆
Diphosphor trioxide: P₂O₃
phosphor trichloride : PCl₃
Phosphor penta chloride: PCl₅
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Molecular compounds
Polyatoms Molecular Compounds:
Poly atoms molecular are the composed of more
than two kinds of non metal atoms.
Carbon dihydro dichloride :CH₂Cl₂
Carbon difluoro dichloride : CF₂Cl₂
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
48
Symbols and Periodic Table Locations
of Some Monatomic Ions
Copper forms either
copper(I) or copper(II) ions.
Titanium forms both
titanium(II) and
titanium(IV) ions.
What is the charge on a
zirconium(IV) ion?
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
49
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
50
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
51
-The acetate ion is also presented as CH₃COO⁻ .
-The prefix “ bi “ means that the ion contains a replaceable
H atom, this should not be confused with the prefix “ di “
which means two ( usually used to represent a doubling of
simpler unit ).
-The prefix “ thio- “ means that sulfur atom has replaced
an oxygen atom.
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
52
Hydrates
A hydrate is an ionic compound in which the
formula unit includes a fixed number of water
molecules associated with cations and anions
Examples:
BaCl2 . 2 H2O
CuSO4 . 5 H2O
EOS
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
53
Hydrates (cont’d)
How many atoms are in one
formula unit of copper(II)
sulfate pentahydrate?
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
54
Example 2.6
Write the molecular formula and name of a compound
for which each molecule contains six sulphor atoms and
four phosphorus atoms.
Aa) P₄S₆
b) tetra phosphorous hexa sulphide
Example 2.7
Write (a) the molecular formula of phosphorus
pentachloride and (b) the name of S2F10.
Aa) PCl₅
b) S2F10 disulphorous decaflouride
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
55
Example 2.8
Determine the formula for (a) calcium chloride
and (b) magnesium oxide.
Aa) CaCl₂
b) MgO
Example 2.9
What are the names of (a) MgS and (b) CrCl3?
Aa)MgS magnesium sulphide
b)CrCl₃ chromium trichloride
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
56
Example 2.10
Write the formula for (a) sodium sulfite and (b)
ammonium sulfate.
Aa) Na₂SO₃
b) (NH₄) ₂SO₄
Example 2.11
What is the name of (a) NaCN and (b) Mg(ClO4)2?
Aa)Sodium cyanide
b)Magnesium di-perchlorate
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
57
Cumulative Example
Show that the following experiment is consistent with the
law of conservation of mass (within the limits of
experimental error): A 10.00-g sample of calcium
carbonate was dissolved in 100.0 mL of hydrochloric
acid solution (d = 1.148 g/mL). The products were
120.40 g of solution (a mixture of hydrochloric acid and
calcium chloride) and 2.22 L of carbon dioxide gas (d =
0.0019769 g/mL).
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
58
Introduction to Compounds
Q1- What is the mole ( molar mass ) of the
following compounds :
Na₂SO₄, HNO₃, P₂O₅
Q2- How many moles are in 200 g. of potassium
permanganate KMnO₄.
Q3- How many sodium atoms (Na) in 460 grams of
this metal.
EOS
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two
Example 3.5 An Estimation Example
Which of the following is a reasonable value for the
number of atoms in 1.00 g of helium?
(a) 4.1 × 10–23
(c) 1.5 × 1023
(b) 4.0
(d) 1.5 × 1024
AThe molar mass of Helium is 4 g. , so the actual
value is 0.25 x 6.023x10²³ and the reasonable value is
answer ( c) .
Prentice Hall © 2005
General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry
Chapter Two