1. Atoms, Molecules and Ions
Chapter 2
Atoms, Molecules and Ions

2. Chapter 2 (p.49-68) Atomic number , mass number and isotopes.
The periodic table .
Molecules and ions .
Chemical formulas .
Naming compounds

4. {لاَ يَعْزُبُ عَنْهُ مِثْقَالُ ذَرَّةٍ فِي السَّمَاوَاتِ وَلاَ فِي الأَرْضِ وَلاَ أَصْغَرُ مِن ذَلِكَ وَلاَ أَكْبَرُ إِلاَّ فِي كِتَابٍ مُّبِينٍ} (سبأ: 3).
Atomic Structure
Elements: are composed of extremely small particles called atoms.
Atom: is the basic unit of an element that can enter into chemical combination

5. Electron (e) (-ve charge) Proton (p) (+ve charge)
Atom consists of:
Electron (e) (-ve charge)
Proton (p) (+ve charge)
Neutron (n) (neutral)
Subatomic Particles

6. mass p = mass n = 1840 x mass e-
2.2

7. 2.3 Atomic number , mass number and isotopes.

8. No. of neutron= mass No. (A)- atomic No. (Z)
Atomic number (Z) = number of protons in nucleus.
In the neutral atom: the No. of protons is equal the No. of electrons.
So the atomic number also= No. of electrons.
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutron
No. of neutron= mass No. (A)- atomic No. (Z)
Mass Number X A Z
Element Symbol
Atomic Number
Examples: 4 H 1 C 12 6 Kr 83 36 He 2
2.3

9. Define the element X ? Example 2.1
Give the number of protons, neutrons, and electrons in each of the following species:
elements
Atomic Number (Z) 11 8 6 80
Mass Number (A) 20 22 17 14
200
No. of electrons (e)
No. of protons (p)
No. of neutrons (n) 9
120 Na 20 11 Na 22 11 O 17 8 C 14 6 Hg
200 80
Define the element X 63 29 ?
The element with atomic number 29 is cupper (Cu) and its mass number is 63

10. Do You Understand Isotopes?
How many protons, neutrons, and electrons are in C 14 6 ?
6 protons, 8 =(14 - 6) neutrons, 6 electrons
How many protons, neutrons, and electrons are in C 11 6 ?
6 protons, 5 =(11 - 6) neutrons, 6 electrons

11. Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei1
H (D) 2
H (T) 3
Isotopes of
Hydrogen
1 P P P
0 n n n C 12 6 13 14
examples: U
235 92
238
Isotopes of an atom have essentially the same chemical behavior.

12. C 12 6 13 14
Isotopes of an atom have essentially the same chemical behavior.

13. U
235 92
238
uranium-235
uranium-238

14. Practice Exercise:
How many protons, neutrons, and electrons are in the following isotopes

15. P=29 n=34 e=29 Practice Exercise:
How many protons, neutrons, and electrons are in the following isotope of copper: 63Cu?
How can I get the atomic number: look at the periodic table → then find the number of p, n & e.
P=29
n=34
e=29

16. Allotropes
Allotrope is one of tow or more distinct forms of an element as O2 , O3 .
O-O (O2) and O3
Allotropes are different structural forms of the same element and can exhibit quite different physical properties and chemical behaviors.

17. Allotropes
Graphite
Diamond
the carbon atoms are bonded together in a tetrahedral lattice arrangement.
the carbon atoms are bonded together in sheets of a hexagonal lattice arrangement.

18. The Difference between Allotropes and Isotopes
allotropes of an element differ on the structure of the same atoms, (i.e. how the atoms are arranged).
isotopes of the element differ on the number of neutrons of the atoms (i.e. the composition of subatomic particles in an atom).

19. 2.4 The periodic table

20. Periodic Table Alkaline Earth Metal Noble Gases Halogen Alkali Metal
Group
Period
2.4

21. The periodic Table: is a chart in which elements having similar chemical and physical properties are grouped together.
The elements in the modern periodic table are arranged by atomic number

22. Metal .
Nonmetal .
Metalloid .

23. Positive ions are called: positrons. anions. cations. nucleons.
The elements located in group 7A of the periodic table are called:
alkali metals.
noble gases.
chalcogens.
halogens.
What are the ions present in the compound (NH4)2SO4 ?
NH3, H2, and SO2
N3–, H+, S2–, O2–
NH42+ and SO4–
NH4+ and SO42– (3 IONS)
(NH4+)2 and SO42–

24. 1- Selenium (34Se) element is: (a) a nonmetal (b) found in group 6A
(c) both a and b
2- Gallium (Ga) element is found in the periodic table in
(a) period 3, group 1B
(b) period 3A, group 4
(c) period 4, group 1A
(d) period 4, group 3A
3- Which of the following sets of elements is expected to have similar chemical properties?
a) Sulfur and phosphorous
b) Sulfur and oxygen
c) Sulfur and argon
4- Which of these elements is most likely to be a good conductor of electricity? 
Which of the following is metal?
A. N
B. S
C. He
D. Fe
السؤال الثاني حددي موقع العنصر ثم حددي رقم المجموعة و الدوره لاتنسي أن تقومي بعد الدوره الاولى التي فيها الهيدروجين, السؤال 3 العناصر التي تقع في نفس المجموعه هي العناصر التي لها نفس الخواص الكيميائية و الفيزيائية , سؤال 4 العنصر الموصل الجيد للكهرباء و الحراره كانه يسأل عن الفلز .... غيري السؤالين الى غير الفلز و لاحظي الفرق

25. Chemistry In Action Natural abundance of elements in Earth’s crust
Natural abundance of elements in human body
2.4

26. 2.5 molecules and ions.

27. The monatomic gases are the single atoms of noble gases; He, Ne, Ar, Kr, Xe, Rn.
A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical forces. H2
H2O
NH3
CH4
Molecule
Polyatomic molecule: contains more than two atoms
Diatomic molecule: contains only two atoms
H2, N2, O2, Br2, HCl, CO,
NO, KCl
O3, H2O, NH3, CH4 ,NaOH

28. Ion is an atom, or group of atoms, that has a net positive or negative charge.
Cation
an ion with a +ve charge
(lose electron/s)
Anion
an ion with a -ve charge
( Gain electron/s)
Monoatomic cation
Polyatomic cation
Monoatomic anion
Cl-, Br-,S2-
Polyatomic anion
OH-, PO43-
Na+, K+, Mg2+
Al3+, N3-
NH4+

29. Which of the following is an example of monatomic anion?
A) Mg+2
B) NH4+1
C)O-2
D) SO4-2
Which of the following is an example of polyatomic cation?
A) Mg+2
B) NH4+1
C)O-2
D) SO4-2

30. Cation anion 11Na 17Cl 11 protons 11 protons 11 electrons 10 electrons

31. Cation anion 11Na 17Cl 11 protons 11 protons 11 electrons 10 electrons

33. Do You Understand Ions? How many protons and electrons are in ? Al27 13 3+
13 protons, 10 (13 – 3) electrons
How many protons and electrons are in ? Se 78 34 2-
34 protons, 36 (34 + 2) electrons

34. Different Ions of Some Elements
Metals tend to form cations
Nonmetals tend to form anions
2.5

35. Metals are on the left side of the chart (green color)
Nonmetals are on the right side of the periodic table (with the exception of H) (blue).
Metalloids border the stair-step line (with the exception of Al, Po, and At).
Metals are on the left side of the chart (green color)

36. B 11 5 P 31 15 3- Au
196 79 Rn
222 86 26
18-3=15
54-26=28
26-2=24 86 2+

37. 2.6 chemical formulas.

38. 2.6 الصيغة الجزيئية الصيغة البنائية نموذج الكرة والعصا
نموذج ملء الفراغ
2.6

39. من الصيغة الجزيئية نستطيع إيجاد الصيغة الأولية والعكس غير صحيح
تحتوي على العدد الصحيح من ذرات كل عنصر يدخل في تركيب أصغر وحده في المادة (الجزئ)
من الصيغة الجزيئية نستطيع إيجاد الصيغة الأولية والعكس غير صحيح
A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance
الصيغة الأولية
أبسط صورة للجزئ تعطي نسب وجود الذرات المكونة للجزئ بأصغر نسبة وليس من الضروري أن تعطي العدد الصحيح للذرات
An empirical formula shows the simplest whole-number ratio of the atoms in a substance
H2O
molecular
empirical
H2O
C6H12O6
CH2O O3 O
N2H4
NH2

40. It must be noted that:
The Empirical Formula may the same or different from the Molecular Formula
How can we get the Empirical Formula?
Answer: Divide all the numbers by the largest Common devisor.
e.g. The empirical formula of H2O is H2O
e.g. the empirical formula of C6H12O6 is CH2O (divide the numbers 6, 12 and 6 by the largest common devisor 6)

41. EXAMPLE 2.3 Write the Empirical formulas for the following molecules
Acetylene C2H2 divided by 2 CH
Glucose C6H12O6 divided by 6 CH2O
Nitrous oxide N2O , the Empirical formulas is same as molecular formula N2O
Caffeine C8H10N4O2 divided by 2 C4H5N2O

42. Examples Which of the following is molecular formula
CO2
H2SO4 S8
CH4O
المطلوب الصيغة التي يمكن تبسيطها
الاجابة الثالثة هي الوحيده التي يمكن تبسيطها هي الاجابة الصحيحة
Which of the following is empirical formula
O3 >>>>>> O
H2SO4
S8 >>>>>>> S
C6H12O6 >>>> CH2O
المطلوب الصيغة التي لايمكن تبسيطها
الاجابة الثانية لايمكن تبسيطها هي الاجابة الصحيحة

43. Write the Molecular formula of Methanol and Chloroform, using the structural formulas below:Cl H
Molecular formula
of Methanol
Molecular formula
of Chloroform
CH4O
CHCl3 or
CH3OH

44. acetylene C2H2 CH glucose C6H12O6 CH2O nitrous oxide N2O caffeine
Write the empirical formulas for the following molecules if possible:
Compounds Name
Molecular Formula
Empirical Formula
acetylene
C2H2 CH
glucose
C6H12O6
CH2O
nitrous oxide
N2O
caffeine
C8H10N4O2
C4H5N2O

45. consist of a combination of cations and an anions
Ionic compounds
consist of a combination of cations and an anions

46. the sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero

48. Formula of Ionic Compounds

49. Write the formula of a)chromium sulfate , b)titanium oxide?
Write the formula of magnesium nitride?
Cr 2(SO4)3
2 × +3 = +6
3 × -2 = -6
Cr 3+
SO42-
Mg 3N2
3 × +2 = +6
2 × -3 = -6
Mg 2+
N3-
Ti 2O 4
2 × +4 = +8
4 × -2 = -8
Ti 4+
O 2-

50. 1. An anion is defined as 
A. a charged atom or group of atoms with a net negative charge.
B. a stable atom.
C. a group of stable atoms.
D. an atom or group of atoms with a net positive charge.
2. Atoms of the same element with different mass numbers are called 
A. ions.
B. neutrons.
C. allotropes.
D. chemical families.
E. isotopes.
3. How many neutrons are there in an atom of lead 82Pb whose mass number is 208? 
A. 82
B. 126
C. 208
D. 290
E. none of them

51. 4. An atom of the isotope sulfur-31 consists of how many protons, neutrons, and electrons? (p = proton, n = neutron, e = electron) 
A. 15 p, 16 n, 15 e
B. 16 p, 15 n, 16 e
C. 16 p, 31 n, 16 e
D. 32 p, 31 n, 32 e
E. 16 p, 16 n, 15 e
5. A magnesium ion, Mg2+, has 
A. 12 protons and 13 electrons.
B. 24 protons and 26 electrons.
C. 12 protons and 10 electrons.
D. 24 protons and 22 electrons.
E. 12 protons and 14 electrons.
6. A sulfide ion, S2- , has: 
A. 16 protons and 16 electrons
B. 32 protons and 16 electrons
C. 16 protons and 14 electrons
D. 16 protons and 18 electrons
E. 32 protons and 18 electrons

52. 2.7 naming compounds.

53. Page 64
((+1
((+2

54. Naming Ionic compounds
Metals
Positive ion
Cation
Non metals
Negative ion
Anion
( 1A , 2A ,3A & transition metals)
monoatomic anions
Polyatomic anions
Variable charge metals
Fixed charge metals
(STOCK SYSTEM)
If the metal can form more than 1 cation, the charge is indicated by a Roman numeral in parenthesis after the metal name.
Cations have same name as the metal element
Ag+ silver ion ,Zn2+ zinc ion , Al3+ Aluminum ion , Li+ lithium ion , Ca2+ calcium ion
Fe2+ iron(II) ,Au+ gold(I), Cu+ copper(I) , Fe3+ iron(III) Au3+ gold(III) Cu2+ copper (II) Hg2 +2mercury(I) Hg2+ mercury (II)
Dr. LAILA AL-HARBI

55. Naming Ionic compounds

56. 2. Variable charge metals:
If the metal has more than one oxidation state, the charge is indicated by a Roman numeral in parenthesis after the metal name.
Most of the transition metals are variable charge metals.
E.g. Common metals which exist in more than one positive state:
Fe2+ iron(II) ,Au+ gold(I), Cu+ copper(I) , Fe3+ iron(III) Au3+ gold(III) Cu2+ copper (II) Hg2 +2mercury(I) Hg2+ mercury (II)
3. Polyatomic cations: consist of nonmetals:
H3O+ hydronium ion NH4+ ammonium
Dr. LAILA AL-HARBI

57. Variable charge metals
Dr. LAILA AL-HARBI

58. Metal (cation) Common name of metal cation: NH4+ ammonium
Monovalent elements
Divalent elements
trivalent elements
Transition metals
Lithium (Li+)
Sodium (Na+)
Potassium (K+)
Robidium (Rb+)
Silver (Ag+)
Magnisium (Mg2+)
Calcium (Ca2+)
Strontium (Sr2+)
Barium (Ba2+)
Lead (Pb2+)
Zinc (Zn2+)
Aluminium (Al3+)
Galium (Ga3+)
(Fe2+) iron(II)
(Fe3+) iron(III)
(Cr3+) chromium (III)
(Cu2+) cupper (II)
(Cu+) cupper (I)
(Mn2+) manganese(II)
(Mn3+) manganese(III)
(Mn4+) manganese(IV)
(Mn7+) manganese(VII)
(Sn2+) stannous or tin(II)
(Hg22+) mercury(I)
(Hg2+) mercury(II)
Common name of metal cation: NH4+ ammonium

59. NOTE The cation of two positive charges has the formula Hg2+
Some Cations of variable charge have name for each oxidation state
Example
Fe2+ iron(II) ferrous , Fe3+ iron(III) ferric
Cu+ copper(I) cuprous , Cu2+ Copper (II) cupric
Hg2 +2mercury(I) mercurous
Hg2+ mercury (II) mercuric
Mercury (Hg) is the only metal has this formula when it form cation with only one positive charge :
Hg22+ NOT Hg+
The cation of two positive charges has the formula Hg2+
Dr. LAILA AL-HARBI

62. nonmetal (anion) Hydrogen hydride (H-) Oxygen oxide (O2-)
Nitrogen nitride (N3-)

63. Metals form only type of cation
Nonmetals
Metals form more than one type of cation (Transition Metals)
Group 1A (alkaline Metals): +1
Group 2A (alkaline Earth Metals): +2
Group 3A: +3
Group 5A: -3 (= 5-8)
Group 6A: -2 (= 6-8)
Group 7A (halogens): -1 (= 7-8)

64. B. Naming Anions 1. monoatomic anions: change ending to -ide
E.g. Oxygen→ Oxide Sulfur → Sulfide
Hydrogen →Hydride chlorine → Chloride
Florine → Floride Bromine → Bromide
Polyatomic anions: most end in -ate or -ite; usually contain O (oxy)
Know polyatomic anions on handout.
Carbonate CO3-2 , Nitrate NO3- , Sulfate SO4-2 ,
Phosphate PO4-3
Cyanide CN- , Hydroxide OH- , Oxide O2-2
See table 2.3

65. Nonmetal polyatomic anions
كبريتات ات
كبريتيت يت
(SO42-) sulfate ,
(SO32-) sulfite
(HSO4-) hydrogen sulfate or bisulfate
(PO43-) phosphate (PO33- ) phosphite
(HPO42-) hydrogen phosphate or biphosphate
(H2PO4-) dihydrogen phosphate
(NO3-) nitrate (NO2-) nitrite
(ClO4– ) perchlorate (ClO3- ) chlorate
(CO32–) carbonate (HCO3– ) hydrogen carbonate or bicarbonate

66. Ionic compounds names start with the positive ion (metal) (include Roman numeral in parenthesis ONLY IF metal has variable charge) followed by the negative ion (nonmetal).
NaCl Sodium Chloride
BaCl Barium Chloride
K2O Potassium oxide
KNO Potassium Nitrate
Na2CO Sodium Carbonate
FeCl Iron(II) Chloride → ferrous Chloride
FeCl Iron(III) Chloride → ferric Chloride
Cr2S Chromium(III) Sulfide
(NH4)3PO4 Ammonium Phosphate
Cu(NO3)2 Cupper(II)nitrate
PbO Lead(II) oxide

69. Name the following compounds: (a) Cu(NO3)2
Example 2.5 p61:
Name the following compounds:
(a) Cu(NO3)2
1. Cation: Copper cation (can form two
types of cation →Stock system) →
Copper (II)
2. Anion: NO3- anion has a common name
Nitrate
Thus: the name of the compound is:
Copper (II) nitrate
قاعدة تبادل التكافؤات
Dr. LAILA AL-HARBI

70. Potasium dihydroen phosphate
(b) KH2PO4
1. Cation: K form only one type of cation
→ Potassium Note: not potassium (I)
2. Anion: H2PO4- has a common name
dihydrogen phosphate
Thus: the name of the compound is:
Potasium dihydroen phosphate

71. Write the chemical formula for the following compounds
Mercury(I)nitrite
Hg2 (NO2)2
Cesium sulfide
Ce2S
Calcium phosphate
Ca3 (PO4)2
Write the chemical formula for the following compounds
Rubidium sulfate
Rb 2 SO4
Barium hydride
BaH 2
Dr. LAILA AL-HARBI

72. Name the following ionic compounds:
Cu(NO3)2
Cupper(II) nitrate
KH2PO4
Potassium dihydrogen phosphate
NH4SCN
Ammonium thiocyanate
H2O2
Hydrogen peroxide
Li2SO3
Lithium sulfite
Ca3(PO3)2
Calcium phosphite
KMnO4
Potassium permenganate
Hg2Cl2
Mercury(I) chloride
K2CrO4
Potassium chromate
Br2O7
Dibromine heptoxide

73. Write formulas for the following ionic compounds:
Manganese(II) oxide
MnO
Potassium hydrogen phosphate
K2HPO4
NH4ClO2
Ammonium chlorite
Lead hydroxide
Pb(OH)2
Sodium bicarbonate
NaHCO3
Barium cyanide
Ba(CN)2
RbHSO4
Rubidium hydrogensulfate
Mercury(II) bromide
HgBr2
Strontium hydride
SrH2

74. يتكون الإسم من الفلز يليه اللافلز
Ionic Compounds
often a metal (cation) + nonmetal (anion)
The cation is always named first and the anion second
anion (nonmetal), add “ide” to element name
المركبات الأيونية
يتكون الإسم من الفلز يليه اللافلز
يضاف ide لللافلز

75. Ionic compounds
Binary compounds are compounds formed from just two elements
BaCl2
barium chloride
K2O
potassium oxide
2. Ternary compounds are compounds formed from three elements.
Mg(OH)2
magnesium hydroxide
KCN
potassium cyanide
2.7

76. Molecular Compounds 1- Consists of (metalloid + nonmetal)
or (nonmetal + nonmetal)
Many molecular compounds are binary compounds
2- common names of some molecular compounds
Diborane
B2H6
Methane
CH4
Silane
SiH4
Ammonia
NH3
Phosphine
PH3
Water
H2O
Hydrogen sulfide
H2S
المركبات الجزيئية
تتكون من أشباه فلزات + لا فلزات
لا فلزات + لا فلزات
معظم المركبات الجزيئية تكون ثنائية العنصر (تتكون من عنصرين فقط)
بعضها له أسماء شائعه مثل
H2O, NH3, CH4
العنصر الأخير يضاف لنهايته ide
3- last element ends in -ide

77. (HCl) H(1A) and Cl(7A), so hydrogen is 1st, the name is
4- element further left in periodic table is 1st (less electronegative)
(HCl) H(1A) and Cl(7A), so hydrogen is 1st, the name is
hydrogen chloride
تكتب العناصر الموجوده يسار الجدول الدوري أو الأقرب لليسار أولا.
المركبات المحتوية على أكثر من ذرة من نفس العنصر يعبر عن عدد الذرات للعنصر لها باستخدام البادئات اليونانية
5- element closest to bottom of group is 1st (less electronegative)
(SiC) Si(4A) and C also belongs to (4A) ,but (Si) is closest to bottom of the group, so silicon is 1st ,
the name is silicon carbide

78. 6- if more than one compound can be formed from the same elements, use prefixes to indicate number of each kind of atom.
Examples

79. Note Note that mono- is never used for the first element
For oxides, the ending “a” in the prefix is omitted.
N2O4 dinitrogen tetroxide not (dinitrogen tetraoxide)
For oxides, the ending “o” in the prefix is omitted.
N2O dinitrogen monoxide not (dinitrogen monooxide )
Dr. LAILA AL-HARBI

80. Examples of Molecular CompoundsHI
hydrogen iodide
PF3
phosphorus trifluoride
H2O2
Hydrogen peroxide
N2O4
dinitrogen tetraoxide
TOXIC!
NO2
nitrogen dioxide
N2O
dinitrogen monooxide
Laughing Gas
ICl3
Iodine trichloride
2.7

81. Name the following molecular compounds:
SO2
Sulpher dioxide
SiCl4
Silicon tetrachloride
BrF7
Bromine heptaflouride
P4O10
Tetraphosphorus decoxide
Cl2O7
Dichlorine heptoxide
CH4
Methane
CS2
Carbon disulphide
Br2O7
Dibromine heptoxide

82. Sulphur tetraflouride SF4
Write formulas for the following molecular compounds:
Sulphur tetraflouride
SF4
Dinitrogen pentoxide
N2O5
Sulfur trioxide
SO3
Disilicon hexabromide
Si2Br6
Phosphorus pentachloride
PCl5
Tetraphosphorus decasulphide
P4S10
Nitrogen peroxide
N2O2
Carbon monoxide CO
Iodine heptaflouride
IF7

83. Fill the blanks in the following table
name
formula
anion
cation
Barium bicarbonate
Ba(HCO3)2
HCO3-
Ba2+
Iron(III)nitrite
Fe (NO2)3
NO2-
Fe3+
Hyrdogen flouride HF F- H+
Manganise(IV)oxide
MnO2
O2-
Mn4+
Sodium peroxide
Na2O2
O22-
Na+
Cesium chlorate
CsClO3
ClO3-
Cs+
Lithium nitride
Li3N
N3-
Li+

84. Which of these pairs of elements would be most likely to form an ionic compound? 
(a) P and Br
(b) Cu and K
(c) C and O
(d) O and Zn
(e) Al and Rb
Which of these pairs of elements would be most likely to
form a molecular compound?
Na and Br (b) C and O
Ca and O (d) Zn and O
Mg and Cl

85. Which of the following compounds is named lithium carbonate?8.
Which of the following compounds is named lithium carbonate? A)
Na2CO3 B)
LiHCO3 C)
LiCO D)
Li2CO3 9.
What is the name of KClO? A)
potassium chlorite B)
potassium chloride C)
potassium hypochlorite D)
potassium oxide
10.
What is the formula for ammonium sulfate? A)
NH4SO4 B)
NH4(SO4)2 C)
(NH4)2SO4 D)
NH4S