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. {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
Atom consist of:
Electron (e) (-ve charge)
Proton (p) (+ve charge)
Neutron (n) (neutral)
Out of the nucleus
Inside the nucleus

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

5. Cathode Rays Experiment for Discovering Electrons By Joseph John Thomson (1856-1940)

6. Anode Rays Experiment for Discovering Protons By Goldshtien

7. Atomic number, Mass number and Isotopes
Atomic number (Z) = number of protons or electrons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons A
Mass Number X
Element Symbol Z
Atomic Number
Examples: C 12 6 Kr 83 36

8. 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

9. Isotopes
Isotopes are atoms of the same element (X) with different numbers of neutrons (mass number)
Examples of Isotopes

10. Do You Understand Isotopes?
How many protons, neutrons, and electrons are in C 14 6 ?
6 protons, 6 electrons, 8 (14 - 6) neutrons
How many protons, neutrons, and electrons are in C 11 6 ?
6 protons, 6 electrons, 5 (11 - 6) neutrons
Define the element X 63 29 ?
The element with atomic number 29 is cupper (Cu)
and its mass number is 63
2.3

11. Allotropes
Allotrope is one of two or more distinct forms of an element as O2 , O3
Examples of Allotropes
* Oxygen O=O (O2) and Ozone O3
* Diamond and Graphite

12. Allotropes
Allotropes are different structural forms of the same element and can exhibit quite different physical properties and chemical behaviors.

13. Diamond and Graphite
Graphite
Diamond

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

15. increasing in atomic number
Periodic Table
is a chart in which elements having similar chemical properties are grouped together in this table the elements are arranged by
increasing in atomic number
Alkali Earth Metal
Noble Gas
Halogen
Alkali Metal
Group
Period
2.4

16. Periodic Table in Latin1 H
1.0
Hydrogenium 2 He
4.0
Helium 3 Li
6.9
Litium 4 Be
9.0
beryllium
ATOMIC
MASS
NUMBER 5 B
10.8
Borum 6 C
12.0
Carboneum 7 N
14.0
Nitrogenium 8 O
15.9 Oxygenium 9 F
18.9
Fluorum 10 Ne
20.1
Neon 11 Na
22.9
Natrium 12 Mg
24.3
Magnesium 13 Al
27.0
Aluminium 14 Si
28.0
Silicium 15 P
30.9
Phosphorus 16 S
32.0
Sulphur 17 Cl
35.4
Chlorum 18 Ar
39.9
Argon 19 K
39.0
Kalium 20 Ca
40.0
Calcium 21 Sc
44.9
Scandium 22 Ti
47.8
Titanium 23 V
50.9
Vanadium 24 Cr
51.9
Chromium 25 Mn
54.8
Manganum 26 Fe
55.8
Ferrum 27 Co
58.9
Cobaltum 28 Ni
58.6
Niccolum 29 Cu
63.5
Cuprum 30 Zn
65.3
Zincum 31 Ga
69.7
Gallium 32 Ge
72.6
Germanium 33 As
74.9
Arsenicum 34 Se
78.9
Selenium 35 Br
79.9
Bromum 36 Kr
83.8
Krypton 37 Rb
85.4
Rubidium 38 Sr
87.6
Strontium 39 Y
88 .9
Yttrium 40 Zr
91.2
Zirconium 41 Nb
92.9
Niobium 42 Mo
95.9
Molybdaenum 43 Tc
98.9
Technetium 44 Ru
101.0
Uthenium 45 Rh
102.9
Rhodium 46 Pd
106.4
Palladium 47 Ag
107.8 Argentum 48 Cd
112.4
Cadmium 49 In
114.8
Indium 50 Sn
118.7
Stannum 51 Sb
121.7
Stibium 52 Te
127.6
Tellurium 53 I
126.9
Iodium 54 Xe
131.2
Xenon 55 Cs
132.9
Caesium 56 Ba
137.3
Barium 71 Lu
174.9
Lutetium 72 Hf
178.4
Hafnium 73 Ta
180.9
Tantalum 74 W
183.8
Wolframium 75 Re
186.2
Rhenium 76 Os
190.2
Osmium 77 Ir
192.2
Iridium 78 Pt
195.0
Platinum 79 Au
196.9
Aurum 80 Hg
200.5
Hydrargyrum 81 Tl
204.3
Thallium 82 Pb
207.2
Plumbum 83 Bi
208.9
Bismuthum 84 Po
Polonium 85 At
209.9
Astatium 86 Rn
222.0
Radon 87 Fr
223.0
Francium 88 Ra
226.0
Radium
103 Lr
261.1
Lawrencium
104 Rf
Rutherfordium
105 Db
262.1
Unnilpentium
106 Sg
263
Unnilhexium
107 Bh
264.1
Unnilseptium
108 Hs
265.1
Unniloctium
109 Mt
268
Unnilennium
110
Uun
269
Ununnilium
111
Uuu
272
Unununium
112
Uub
277
Ununbium
114
Uuq
289
Ununquadium
116
Uuh
Ununhexium
118
Uuo
293
Ununoctium
Periodic Table in Latin 1 2A 3A 4A 5A 6A 7A 2 3 8B 3B 4B 5B 6B 7B 1B 2B 4 5 6 7 57 La
138.0
Lanthanum 58 Ce
140.1
Cerium 59 Pr
140.9
Praseodymium 60 Nd
144.9
Neodymium 61 Pm
Promethium 62 Sm
150.3
Samarium 63 Eu
151.2
Europium 64 Gd
157.2
Gadolinium 65 Tb
158.9
Terbium 66 Dy
162.9
Dysprosium 67 Ho
164.9
Holmium 68 Er
168.2
Erbium 69 Tm
168.9
Thulium 70 Yb
173.0
Ytterbium 89 Ac
232
Actinium 90 Th
121.0
Thorium 91 Pa
231.0
Protactinium 92 U
238.0
Uranium 93 Np
237.0
Neptunium 94 Pu
244.0
Plutonium 95 Am
243.0
Americium 96 Cm
247.0
Curium 97 Bk
Berkelium 98 Cf
251.0
Californium 99 Es
252.0
Einsteinium
100 Fm
257.0
Fermium
101 Md
258.0
Mendelevium
102 No
259.1
Nobelium
Metals
Metalloids
Nonmetals

17. 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

18. An ion is an atom, or group of atoms, that has a net positive or negative charge.
ion with a negative charge.
If a neutral atom gains one or more electrons it becomes an anion.
Cation:
ion with a positive charge. If a neutral atom loses one or more electrons it becomes a cation.
Monoatomic cation
Polyatomic cation
Monoatomic anion
Cl-, Br-,S2-
N3-
Polyatomic anion
OH-, PO43-
Na+, K+, Mg2+
Al3+
NH4+

19. Cation Anion 11Na 17Cl 11 protons 11 protons 11 electrons 10 electrons

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. Complete the following table:3- 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+

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

23. 2.6

24. molecular empirical An empirical formula tells us which elements are
present and the simplest whole-number ratio of the
atoms in a substance.
A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance.
molecular
empirical
H2O, N2O, CH4, CH3OH, NH3, CO2
C6H12O6
CH2O O3 O
N2H4
NH2 CH
C6H6
2.6

25. 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

26. 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

27. 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
The ionic compound NaCl
2.6

28. SALT - a Cation and an Anion held together by an ionic bond.
opposites attract

29. Write the chemical formula of the following ionic compounds
2 x +3 = +6
3 x -2 = -6
Aluminum Oxide
Al2O3
Al3+
O2-
1 x +2 = +2
2 x -1 = -2
Calcium bromide
CaBr2
Ca2+
Br-
2 x +1 = +2
1 x -2 = -2
Aluminum Oxide
Na2CO3
Na+
CO32-

31. 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 √
C. 208
D. 290
E. none of them

32. 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

33. 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

34. Chemical Nomenclature of
Ionic Compounds
Metal (cation)
nonmetal (anion)
The most reactive metals (green) and the most reactive nonmetals (blue) combine to form ionic compounds.

35. Metal (cation) nonmetal (anion)
Ionic Compounds
Consists of
Metal (cation)
nonmetal (anion)

36. Ionic bond
Li F 2 1 2 1

37. Ionic bond
Li F 2 1 2 1

38. The attraction between
Ionic bond
Li F-1 2 1 2 1
The attraction between
a cation and an anion.

39. Chemical Nomenclature
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
Binary compounds are compounds formed from just two kinds of elements
BaCl2
barium chloride
K2O
potassium oxide
Ternary compounds are compounds formed from three kinds of elements.
Mg(OH)2
magnesium hydroxide
KNO3
potassium nitrate
2.7

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

41. Metal (cation) Transition metals
Monovalent elements
Divalent elements
trivalent elements
Transition metals
Lithium (Li+)
Sodium (Na+)
Potassium (K+)
Robidium (Rb+)
Cesium (Cs+)
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

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

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

44. 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
(ClO3– ) chlorate (ClO2- ) chlorite
(BrO3– ) bromate (BrO2- ) bromite
(CO32–) carbonate (HCO3– ) bicarbonate

45. 2.7

46. Name the following ionic compounds:
Cu(NO3)2
Copper(II)nitrate
KH2PO4
Potassium dihydrogen phosphate
NH4SCN
Ammonium thiocyanate
Cs2O2
Cesium peroxide
Li2SO3
Lithium sulphite
Ca3(PO3)2
Calcium phosphite
KMnO4
Potassium permenganate
Hg2Cl2
Mercury(I)chloride
K2CrO4
Potassium chromate

47. Write formulas for the following ionic compounds:
Manganese(II)oxide
MnO
Potassium hydrogen phosphate
K2HPO4
Ammonium chlorate
NH4ClO3
Lead hydroxide
Pb(OH)2
Sodium bicarbonate
NaHCO3
Barium cyanide
Ba(CN)2
Rubidium hydrogensulphate
RbHSO4
Mercury(II)bromide
HgBr2
Strontium hydride
SrH2

48. Molecular Compounds 1- Consists of (metalloids + nonmetals) Ex. SiC
Or (nonmetal + nonmetal) Ex. PCl3
2- Many molecular compounds are Binary Compounds
3- common names of some molecular compounds
Diborane
B2H6
Methane
CH4
Silane
SiH4
Ammonia
NH3
Phosphine
PH3
Water
H2O
Hydrogen sulfide
H2S
4- last element ends in -ide

49. 5- 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
6- 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
7- 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

50. Second Element (anion)
Naming of Elements
Element’s symbol
First Element
Second Element (anion) H
Hydrogen
hydride C
Carbon
carbide Si
Silicon
silicide N
Nitrogen
nitride P
Phosphorus
phosphide O
Oxygen
oxide S
Sulpher
sulphide F
fluorine
fluoride Cl
Chlorine
chloride Br
Bromine
bromide I
Iodine
iodide

51. 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

52. 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

53. 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

54. 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+