CHEMISTRY
Chapter 2
Atoms, Molecules, and
Ions
‫‪Daltons' Atomic Theory‬‬
‫نظرية دالتون في الذرة‬
‫نظرية دالتون في الذرة‪:‬‬
‫فرق بين نوعين من المادة وحيدة التكوين‬
‫يعتبرالعالم دالتون أول من ّ‬
‫‪.substance‬‬
‫‪ -1‬عناصر ‪Elements‬‬
‫‪ -2‬مركبات ‪Compounds‬‬
‫ووضع الفرضيات التالية‪:‬‬
‫‪ -1‬الذرة أصغر جزء من العنصر والتتجزأ بالوسائل االعتيادية ‪.‬‬
‫‪ -2‬ذرات العنصر الواحد تتشابه في الخواص الفيزيائية والكيميائية ‪.‬‬
‫‪ -3‬الجزيء أصغر جزء من المركب ‪ ,‬ويتكون من اتحاد ذرتين أو أكثر‬
‫‪2‬‬
‫‪Daltons' Atomic Theory‬‬
‫نظرية دالتون في الذرة‬
‫‪ -4‬جزيئات المركب الواحد متشابهة في الخواص الفيزيائية والكيميائية ‪.‬‬
‫‪ -5‬الذرة مصانة في التفاعل الكيميائي ‪.‬‬
‫‪ -6‬التفاعل الكيميائي ‪ ,‬يحدث بين الذرات ‪ ,‬وما هو في الحقيقة سوى إعادة‬
‫لترتيب الذرات‪.‬‬
‫‪.‬‬
‫‪3‬‬
Daltons' Atomic Theory
‫نظرية دالتون في الذرة‬
John Dalton and his Atomic Theory
Introduction:
Dalton was the first to distinguish between two
types of substance:
-Elements
-Compounds
1-Atom is the smallest unit of the element and
cannot be broken down by ordinary
chemical operations.
4
Daltons' Atomic Theory
‫نظرية دالتون في الذرة‬
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-Aoms are conserved during the chemical
reaction.
6- the chemical reaction takes place between the
atoms, and the chemical reaction is a new
rearrangement of the atoms to produce new
compounds.
5
INTERNATIONAL UNVERSITY
FOR SCIENCE & TECHNOLOGY
‫قوانين االتحادات الكيميائية‬
The Combination Laws in
Chemistry
6
‫قانون انحفاظ المادة‬
‫‪The Conservation Law in Chemistry‬‬
‫‪Lavoisier's Law‬‬
‫المادة مصانة في التفاعل الكيميائي ‪ ,‬ومجموع كتل المواد يبقى ثابتا اليتغ ّيرقبل التفاعل وبعد‬‫التفاعل ‪.‬‬
‫‪-The mass is conserved during the chemical reaction, and the‬‬
‫‪total masses remain unchanged.‬‬
‫تحول من شكل إلى شكل آخر ‪.‬‬
‫المادة التفنى والتخلق من عدم ‪ ,‬وإنما هناك ّ‬
‫‪- Mass is neither created nor destroyed‬‬
‫ مجموع أوزان المواد الداخلة في التفاعل ‪ ,‬يساوي مجموع أوزان المواد الناتجة عن‬‫التفاعل ‪.‬‬
‫‪-The sum of reactant masses is equal to the sum of product‬‬
‫‪masses.‬‬
‫‪7‬‬
‫قانون انحفاظ المادة‬
The Conservation Law in Chemistry
Lavoisier's Law
-The mass is conserved during the
chemical reaction, and the total masses
remain unchanged.
- Mass is neither created nor destroyed
-The sum of reactant masses is equal to the
sum of product masses.
8
‫‪The Conservation Law in‬‬
‫‪Chemistry‬‬
‫‪Lavoisier's Law‬‬
‫قانون مصونية المادة على ضوء نظرية دالتون ‪: After Dalton's theory‬‬
‫حيث أن التفاعل الكيميائي يحدث بين الذرات ‪ ,‬فإن قانون المصونية يكتي بالشكل ‪:‬‬
‫إن مجموع أعداد الذرات الداخلة في التفاعل ‪ ,‬يساوي مجموع أعداد الذرات الناتجة عن‬
‫التفاعل ‪.‬‬
‫قانون مصونية المادة على ضوء نظرية النسبية آلينستاين ‪:‬‬
‫بعد أفكار تحول المادة إلى طاقة ‪ ,‬فأن قانون المصونية و يكتب بالشكل ‪:‬‬
‫إن مجموع أوزان المواد الداخلة في التفاعل ‪ ,‬يساوي مجموع أوزان المواد الناتجة عن‬
‫التفاعل و مع األخذ بعين االعتبار ‪ ,‬تحول المادة إلى طاقة في التفاعالت الناشرة للحرارة‬
‫‪ ,‬وتحول الطاقة إلى مادة في التفاعالت الماصة للحرارة ‪.‬‬
‫‪9‬‬
The Conservation Law in
Chemistry
Lavoisier's 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.
10
‫قانون النسب الثابتة أو قانون بروست‬
‫‪Proust's Law or Definite Proportions Law‬‬
‫قانون النسب الثابتة ‪: definite proportions law‬‬
‫إذا اتحد عنصران معا لتشكيل مركب ما ‪ ,‬فإن اتحادهما يتم وفق نسبة وزنية ثابتة ‪.‬‬
‫فالهيدروجين يتحد مع األوكسجين لتشكيل الماء ‪ ,‬وتكون النسبة ‪2grams/16grams‬‬
‫هي نسبة وزنية ثابتة ‪.‬‬
‫‪H₂O‬‬
‫)‪2g/16g (definite ratio‬‬
‫→ ‪H₂ + O‬‬
‫‪2g‬‬
‫‪16g‬‬
‫قانون النسب الثابتة بشكل عام ‪: Proust 'Law in general‬‬
‫في أي مركب هناك نسبة وزنية ثابتة بين أوزان العناصر المشكلة لهذا المركب ‪.‬‬
‫فحمض الكبريت ‪ ,H₂SO₄‬تكون نسبة أوزان الهيدروجين للكبريت لألوكسجين ‪ ,‬مساوية‬
‫‪2g/32g/64g‬‬
‫‪11‬‬
‫قانون النسب الثابتة أو قانون بروست‬
Proust's Law or Definite Proportions Law
If tow elements combine to form a compound, their
combination will occur according to a fixed mass
ratio, hydrogen combines with oxygen to form
water with a mass ratio 2grams/16grams
H₂ + O → H₂O
2g
16g
2g/16g (definite ratio)
Proust 'Law:
In any compound, there is a fixed ratio of masses
between the elements of this compound.
in other wards:
All samples of the same compound have the same
composition and the same properties.
12
‫قانون النسب الثابتة أو قانون بروست‬
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
12g/32g is a fixed ratio.
Example(2):
In H₂SO₄ compound 2g/32g/64g is a fixed mass
ratio.
.
13
‫قانون النسب الثابتة أو قانون بروست‬
Proust's Law or Definite Proportions Law
Example
The mass ratio of oxygen to carbon in the compound
carbon monoxide is 12/16. What mass of oxygen which
is needed to react with 0.3 g of carbon, and what is
mass of produced CO?
Solution:
C
+
O ----------------- CO
12
16
0.3
x
The mass of oxygen = 0.3x 16/12 = 0.4 g
The mass of carbon monoxide= 0.3 + 0.4 = 0.7 g
14
‫قانون النسب الثابتة أو قانون بروست‬
‫‪Proust's Law or Definite Proportions Law‬‬
‫قانون النسب الثابتة على ضوء نظرية دالتون ‪:‬‬
‫حيث أن التفاعل الكيميائي يحدث بين الذرات ‪ ,‬يمكن‬
‫صياغة قانون بروست بالشكل التالي ‪:‬‬
‫في أي مركب هناك نسبة عددية ثابتة بين ذرات العناصر‬
‫المشكلة لهذا المركب ‪.‬‬
‫ففي حمض الكبيرت و تكون نسبة ذرات الهيدروجين‬
‫للكبريت لألوكسجين مساوية ‪2/1/4‬‬
‫‪15‬‬
Law of Multiple Proportions (cont’d)
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
1612
C + O₂ → CO₂
12 32
Ratio of oxygen-to-carbon in CO2
is exactly twice the ratio in CO.
the 16/32=1/2 is a simple ratio
16
Law of Multiple Proportions
(cont’d)
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?
Compounds I–IV are N2O, N2O3, N2O4, N2O5
•
1:3:4:5
17
The Discovery of Atomic Structure
• Atoms are the building blocks of matter.
• The ancient Greeks were the first to postulate that matter
consists of indivisible constituents.
• Later scientists realized that the atom consisted of
charged entities.
The Atom
Class Practice Problem
• The diameter of a U.S. penny is 19mm. The diameter of
a copper atom, by comparison, is only 2.6 angstroms (Å).
How many copper atoms could be arranged side by side
in a straight line across the diameter of a penny?
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.
21
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
22
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.
23
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.
24
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.
25
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
26
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.
27
Elements and Symbols
-Usually for the simplicity, we represent the elements
by symbols, using the initial letter of the name in
capital form, starting by the old known elements,
so Carbon is represented by the letter C, but
Calcium is represented by the symbol Ca and Cobalt
by the symbol Co, ……, Nitrogen is represented by
the symbol N and Nickel by the symbol Ni, etc….
In general we represent the elements by one capital
letter or by two letters, the first is in capital form,
while the second letter suppose to be in small
form.
Keys and Terms
Isotopes
in Chemistry
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:
¹²₆C, ¹³₆C, ¹⁴₆C
The isotope ¹⁴₆C , is radioactive.
29
Isotopes
Atomic
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.
30
Example :
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
31
Example:
Which of the following pairs of symbols represent
isotopes?
Example:
Indicate the numbers of protons, neutrons and
electrons in the following atoms:
32
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
33
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.
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.
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.
37
Subatomic Particles
Protons and neutrons are located at the center of
an atom (at the nucleus).
Electrons are dispersed around the nucleus.
38
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.
39
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.
40
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 .(elements in the same
vertical group are alike in the physical and
chemical properties)
41
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.
- more than 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.
42
Main Elements and Transition
Elements
The elements of the periodic table are two types:
- Main Elements :where the electrons 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.
43
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.
44
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.
45
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.
46
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.
47
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
48
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
49
Nomenclature
Nomenclature: is the method for naming compounds
and writing formulas for compounds.
We could have a specific name for each compound—
but we would have to memorize each one!
-Can you imagine having to memorize the names of
half a million different inorganic compounds?
Twenty million organic compounds??
-Instead we have a systematic method— conventions
and rules—for naming compounds and writing
formulas.
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
Ions and ionic compounds
Polyatoms 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
52
Binary Molecular Compounds
Binary Molecular Compound: is formed by two
kinds of nonmetal atoms:
e.g., CO, NO, HF, NO₂, SF₄
Molecular formulas are usually written with the
more “metallic” first – “metallic” means farther
left in the period and lower in the group
EOS
53
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
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
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
57
Acids Nomenclature
Notice that the acid name is related to the anion name.
HCl: Hydrochloric acid (chloride ion)
HBr:Hydro bromic acid (bromide ion)
H₂S: Hydrosulfuric acid (sulfide ion)
In the oxyacids:
H₃PO₄: Phosphoric acid, phosphate ion
HNO₃: Nitric acid, nitrate ion
H₂SO₄: Sulphoric acid, sulphate ion
HClO₃: Chloric acid, chlorate ion
HClO₄: Perchloric acid, per chlorate ion
HNO₂: Nitrous acid, nitrite ion
58
Formulas and Names for
Acids
Binary acids start with
hydro and end with
“ic” plus the word acid
Ternary acids simply
use the polyatomic
anion name with “ate”
changing to “ic” plus
the word acid
EOS
59
Example :
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 :
Write (a) the molecular formula of phosphorus
pentachloride and (b) the name of S2F10.
Aa) PCl₅
b) S2F10 disulphorous decaflouride
60
Example :
Determine the formula for (a) calcium chloride
and (b) magnesium oxide.
Aa) CaCl₂
b) MgO
Example :
What are the names of (a) MgS and (b) CrCl3?
AMgS magnesium sulphide(a
Cr(lll)Cl₃ chromium trichloride (b
61
Example :
Write the formula for (a) sodium sulfite and (b)
ammonium sulfate.
ANa₂SO₃(a
(NH₄) ₂SO₄(b
Example :
What is the name of (a) NaCN and (b) Mg(ClO4)2?
ASodium cyanide (a
Magnesium di-perchlorate(b
62
Propane, used in gas grills,
is an alkane with three
carbon atoms
Butyric acid, which gives
rancid butter its “fragrance,”
contains four carbon atoms.
Octane, a component of
gasoline, is a(n) ______ which
contains _____ carbon atoms.
63
Examples
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
Example:
Determine the volume of 1,2,3-propanetriol (glycerol, d
= 1.261 g/mL) that contains 1.00 mol O atoms.
AThe formula of glycerol= C₃H₈O₃The molar mass = 92 g.The number of moles of the glycerol is 1/3 of the number of moles of the oxygen, so we write:
The number of moles of glycerol=1/3 mol.The mass of glycerol= 1/3 x 92 = 30.66 gThe volume = 30.66/1.261 = 24.31 ml.-
Example : An Estimation Example
Which of the following is a reasonable value for the
number of atoms in 1.00 g of helium?
(c) 1.5 × 1023
(a) 4.1 × 10–23
(d) 1.5 × 1024
(b) 4.0
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) .