1. Chapter 2 Atoms, Molecules and Ions
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2. Chapter 2 (p.49-68) Atomic number , mass number and isotopes.
The periodic table .
Molecules and ions .
Chemical formulas .
Naming compounds .
Tables – 2.3 – – 2.6 – 2.7
Examples – 2.3 – 2.4 – 2.5 – 2.6 – 2.7 – 2.8 – 2.9

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

4. 2.3 Atomic number , mass number and isotopes.

5. Atomic number, Mass number and Isotopes
Atomic number (Z) = number of protons+ number of electrons
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutron
Mass Number X A Z
Element Symbol
Atomic Number H 1
H (D) 2
H (T) 3 U
235 92
238
2.3

6. 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
Define the element X 63 29 ?
The element with atomic number 29 is cupper (Cu)
and its mass number is 63
2.3

7. Give the number of protons, neutrons, and electrons
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

8. Isotopes
Isotopes are atoms of the same element (X) with different numbers of neutrons (mass number)
hydrogen
deuterium
tritrium
2.3

10. Allotropes
Allotrope is one of tow or more distinct forms of an element as O2 , O3 .
O-O (O2) and O3
Diamond and Graphite

11. Example for Allotropes
Diamond and Graphite

12. Diamond and Graphite
Graphite
Diamond

13. 2.4 The periodic table .

14. Periodic Table Alkali Earth Metal Alkali Metal Noble Gas Group Halogen
2.4

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

16. 2.5 molecules and ions.

17. A diatomic molecule contains only two atoms
The monatomic molecules 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
A diatomic molecule contains only two atoms
H2, N2, O2, Br2, HCl, CO, NO, KCl
A polyatomic molecule contains more than two atoms
O3, H2O, NH3, CH4, NaOH
2.5

18. cation – ion with a positive charge
An ion is an atom, or group of atoms, that has a net positive or negative charge.
cation – ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation. Na
11 protons
11 electrons
Na+
11 protons
10 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.
Cl-
17 protons
18 electrons Cl
17 protons
17 electrons
2.5

19. A monatomic ion contains only one atom
Na+, Cl-, Ca2+, O2-, Al3+, N3-
A polyatomic ion contains more than one atom
OH-, CN-, NH4+, NO3-
2.5

20. 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
2.5

21. Different Ions of Some Elements
2.5

22. 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+

23. 2.6 chemical formulas.

24. 2.6 الصيغة الجزيئية الصيغة البنائية نموذج الكرة والعصا
نموذج ملء الفراغ
2.6

25. من الصيغة الجزيئية نستطيع إيجاد الصيغة الأولية والعكس غير صحيح
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
الصيغة الجزيئية
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
H2O
molecular
empirical
H2O
C6H12O6
CH2O O3 O
N2H4
NH2
2.6

27. 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

29. 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

30. The ionic compound NaCl
ionic compounds consist of a combination of cations and an anions
the formula is always the same as the empirical formula
the sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero
المركبات الأيونية
صيغتها الجزيئية مطابقة للصيغة الأولية
مجموع الكاتيونات + الأنيونات = صفر
The ionic compound NaCl
2.6

31. Formula of Ionic Compounds
2 x +3 = +6
3 x -2 = -6
Al2O3
Al3+
O2-
1 x +2 = +2
2 x -1 = -2
CaBr2
Ca2+
Br-
2 x +1 = +2
1 x -2 = -2
Na2CO3
Na+
CO32-
2.6

33. 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

34. 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

35. Answer Key 1-A 2-E 3-B 4-B 5-C 6-D
Problems
2.10 – 2.11 – 2.12 – 2.14 – 2.16 – 2.18
– 2.36 – 2.44 – 2.46 – 2.50

36. 2.7 naming compounds.

37. Chemical Nomenclature
المركبات الأيونية
يتكون الإسم من الفلز يلية اللافلز
يضاف ide لللافلز
Ionic Compounds
often a metal + nonmetal
anion (nonmetal), add “ide” to element name
Binary compounds are compounds formed from just two elements
BaCl2
barium chloride
K2O
potassium oxide
Ternary compounds are compounds formed from three elements.
Mg(OH)2
magnesium hydroxide
KNO3
potassium nitrate
2.7

38. Chemical Nomenclature of
Ionic Compounds
Metal (cation)
nonmetal (anion)

39. Metal (cation) Transition metals 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)

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

41. Some common oxygenated anions
(SO42-) sulphate ,
(SO32-) sulphite
(HSO4-) hydrogen sulphate or bisulphate
(PO43-) phosphate (PO33- ) phosphite
(HPO42-) hydrogen phosphate
(H2PO4-) dihydrogen phosphate
(NO3-) nitrate (NO2-) nitrite
(ClO4– ) chlorate (ClO3- ) chlorite
(CO32–) carbonate (HCO3– ) bicarbonate

42. 2.7

43. Transition metal ionic compounds
indicate charge on metal with Roman numerals
In the Stock system the different cations charge are designated with Roman numerals
FeCl2
iron(II) chloride
2 Cl- -2 so Fe is +2
FeCl3
3 Cl- -3 so Fe is +3
iron(III) chloride
Cr2S3
3 S-2 -6 so Cr is +3 (6/2)
chromium(III) sulfide
2.7

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

46. Potassium hydrogen phosphate K2HPO4
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 hydrogensulphate
Mercury(II) bromide
HgBr2
Strontium hydride
SrH2

47. Molecular Compounds 1- Consists of (metalloids + nonmetals)
Or (nonmetal + nonmetal)
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
بعضها له أسماء شائعه مثل
H2O, NH3, CH4
العنصر الأخير يضاف لنهايته ide
6- last element ends in -ide

48. 4- element closest to bottom of group is 1st (less electronegative)
3- 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
4- 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
5- if more than one compound can be formed from the same elements, use prefixes to indicate number of each kind of atom.
(NO) nitrogen monooxide
(NO2) nitrogen dioxide
(N2O) dinitrogen monooxide
2.7

49. 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

50. 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

51. 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

52. 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+

53. 7.
Which compound has the same empirical formula as C6H12O6? A)
C12H24O12 B)
C3H3O3 C)
CH2ON D)
CHO2 8.
Which of the following compounds is named lithium carbonate? A)
Na2CO3 B)
LiHCO3 C)
LiCO D)
Li2CO3 9.
What is the formula for ammonium sulfate? A)
NH4SO4 B)
NH4(SO4)2 C)
(NH4)2SO4 D)
NH4S

54. Answer Key 7-A D C
Problems
2.58 – 2.60 – 2.94