The document provides information about atoms, molecules, and ions. It discusses: - Atomic number and mass number - Isotopes and examples of isotopes of hydrogen - Molecular and empirical formulas - Ionic compounds and how their formulas are determined - Naming common compounds and ions - Acids, bases, and naming acid anions and hydrate compounds

1. Atoms, Molecules,
and Ions
Chapter 2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Dr. Mohammed Tariq Saeed
Office # 138/ 142-A

2. Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Isotopes are atoms of the same element (X) with different
numbers of neutrons in their nuclei
XA
Z
H1
1 H (D)2
1 H (T)3
1
U235
92 U238
92
Mass Number
Atomic Number
Element Symbol
2.3: Atomic Number, Mass Number,
and Isotopes

3. The Isotopes of Hydrogen
Give the number of protons, neutrons, and electrons
in each of the following species:
(a)
(b)
(c)
(d) Carbon-14
Example 2.1

4. 2.4: The Modern Periodic Table
Period
Group
AlkaliMetal
NobleGas
Halogen
AlkaliEarthMetal

5. 2.5: Molecules and Ions:
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
diatomic elements

6. 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
O3, H2O, NH3, CH4
A polyatomic molecule contains more than two atoms:

7. A monatomic ion contains only one atom:
A polyatomic ion contains more than one atom:
Na+, Cl-, Ca2+, O2-, Al3+, N3-
OH-, CN-, NH4
+, NO3
-
Cl-
17 protons
18 electronsCl
17 protons
17 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.

8. Common Ions Shown on the Periodic Table

9. Formulas and Models2.6: Chemical Formulas

10. A molecular formula shows the exact number of
atoms of each element in the smallest unit of a
substance.
An empirical formula shows the simplest
whole-number ratio of the atoms in a substance.
H2OH2O
molecular empirical
C6H12O6 CH2O
O3 O
N2H4 NH2

11. Example 2.2
Write the molecular formula of methanol, an organic solvent
and antifreeze, from its ball-and-stick model, shown below.

12. Example 2.3
Write the empirical formulas for the following molecules:
(a) acetylene (C2H2), which is used in welding torches
(b) glucose (C6H12O6), a substance known as blood sugar
(c) nitrous oxide (N2O), a gas that is used as an anesthetic gas
(“laughing gas”) and as an aerosol propellant for whipped
creams.

13. Ionic compounds consist of a combination of cations
and anions.
• The formula is usually 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

14. The most reactive metals (green) and the most reactive
nonmetals (blue) combine to form ionic compounds.

15. Formulas of Ionic Compounds
Al2O3
2 x +3 = +6 3 x -2 = -6
Al3+ O2-
CaBr2
1 x +2 = +2 2 x -1 = -2
Ca2+ Br-
Na2CO3
2 x +1 = +2 1 x -2 = -2
Na+ CO3
2-

16. Example 2.4
Write the formula of magnesium nitride, containing the
Mg2+ and N3− ions.
Strategy: Compound is electrically Neutral, Total charge on
cations = total charge on anions
.

17. 2.7: Naming Compounds
Chemical Nomenclature
• Binary Ionic Compounds Type-I
– The name of the cation is written first (Metal + non
metal)
– In the name of the anion (nonmetal) add “-ide” to
root element name(in the last)
BaCl2 Barium chloride
K2O Potassium oxide
Mg(OH)2 Magnesium hydroxide
NaCl Sodium chloride

18. Cont’d
• Binary Ionic Compounds Type-II
– Metals have more than one charge, Add numeral
number to indicate the charge on these ions.
– In the name of the anion (nonmetal) add “-ide” to
root element name(in the last)
• Binary Ionic Compounds Type-I
Example:
Compound Ions present Name
NaI Na+, I- Sodium iodide
CaS
Li3N
MgO

19. 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
Example: FeCl2 (Fe has +2 charge) written as
Iron(II) chloride
Ex. Compound Cations Name
FeO
Cr2O4
CuCl2
Al(OH)3

22. Example 2.5
Name the following ionic compound with poly atomic ions:
(a) Cu(NO3)2
(a) KH2PO4
(a) NH4ClO3

23. Example 2.6
Write chemical formulas for the following compounds:
(a) Mercury(I) nitrite
(b) Cesium sulfide
(c) Calcium phosphate

24. • Binary molecular covalent
compounds Type-III: Non-metal-
Nonmetal(Use prefix and suffix)
− The first element in the compound is
named first using the name of the
element.
− The second element is named as
though it were an anion (using the root
name of the element and adding the
suffix (-ide).
− Prefixes are used to denote the
numbers of each atom present.
− Prefix mono- never used for naming
the first element. Ex. CO Carbon
monoxide not mono carbonmonoxide

25. HI Hydrogen iodide
NF3 Nitrogen trifluoride
SO2 Sulfur dioxide
N2Cl4 Dinitrogen tetrachloride
NO2 Nitrogen dioxide
N2O Dinitrogen monoxide
Molecular Compounds: Nonmetal-nonmetal

26. Example 2.7
Name the following molecular compounds and chemical
formula:
(a) SiCl4
(b) P4O10
(c) CO
(d) N2O4
(e) Carbon disulfide
(f) Disilicon hexachloride

27. Example
Learning Check
• Rules: Often drop o and a from the prefix when element begin
with vowel
– Mono – monoxide, tetra - tetroxide
• Example: Systematic name Common name
• N2O Dinitrogen monoxide Nitrous oxide
• NO Nitrogen monoxide Nitric oxide
• NO2
• N2O3
• N2O4
• N2O5
Note: Some compound always referred to by their common names
not systematic names
Ex. H2O:water; NH3: Ammonia; and H2O2 : Hydrogen peroxide

29. An acid can be defined as a substance that yields
hydrogen ions (H+) when dissolved in water.
For example: HCl gas and HCl in
water
• Pure substance, hydrogen
chloride dissolved in water
(H3O+ and Cl−), aqueous
hydrochloric acid is formed
Acid and Base

30. If anion of an acid does not contain oxygen
Use prefix hydro—and suffix –ic attached to the
root name of the element and anion contain ide
in last, It means -ic (acid) -ide (anion)
Non oxy Acid

31. The acids containing oxygen:
The rules for naming oxoanions, anions of
oxoacids, are as follows:
1. When all the H ions are removed from the
“-ic” acid, the anion’s name ends with “-ate.”
2. When all the H ions are removed from the
“-ous” acid, the anion’s name ends with “-ite.”
3. The names of anions in which one or more
but not all the hydrogen ions have been
removed must indicate the number of H ions
present. For example:
– H2PO4
- dihydrogen phosphate
– HPO4
2- hydrogen phosphate
– PO4
3- phosphate

32. An oxoacid is an acid that contains hydrogen,
oxygen, and another element. Anion –ate change
to suffix ic, -ite change to -ous
HNO3 -NO3
1- nitrate nitric acid
H2CO3 -CO3
2- carbonate carbonic acid
H3PO4 -PO4
3- phosphate phosphoric acid
Acid -ate -ic
Acid -ite -ous
HNO2 -NO2
1- nitrite nitrous acid
H2SO3 -SO3
2- sulfite sulfurous acid

33. Example 2.9
Name the following oxo-acid and oxo-anion:
(a)H3PO3
(b)

34. Naming Oxo-acids and Oxo-anions
4 O
3 O
2 O
O

35. A base can be defined as a substance that yields
hydroxide ions (OH-) when dissolved in water.
NaOH sodium hydroxide
KOH potassium hydroxide
Ba(OH)2 barium hydroxide

36. Hydrates are compounds that have a specific
number of water molecules attached to them.
BaCl2•2H2O
LiCl•H2O
MgSO4•7H2O
Sr(NO3)2 •4H2O
barium chloride dihydrate
lithium chloride monohydrate
magnesium sulfate heptahydrate
strontium nitrate tetrahydrate
CuSO4•5H2O CuSO4

38. Organic Chemistry?
A branch of chemistry involving the study of
carbon-containing chemical compounds.
Why is carbon so special?
• Carbon atoms connect with one another
through strong and stable covalent bonds.
• Carbon atoms also readily form bonds with
many other types of atoms. This provides
for a near infinite number of different kinds
of organic compounds.

39. Hydrocarbons
A chemical compound containing only hydrogen and carbon.
Two types of hydrocarbon
A. Saturated Hydrocarbon:
The molecular formula is (Single bond)
The simplest aliphatic compound is alkane
Alkane CnH2n+2
CH4 Methane
CH3-CH3 Ethane
CH3- CH3-CH3 Propane
B. Unsaturated Hydrocarbon : They contain double / triple bonds in the
compounds.
. Alkene CnH2n
Ethylene C2H4 CH2=CH2 ,
Propylene C3H6 CH2=CH-CH3
- Alkynes CnH2n-2
Acetylene,

40. Structural Isomer
Molecules having the same molecular formula but different
structures.

41. Structural Isomer
Formula Number of possible isomers
C5H12 3
C6H14 5
C7H16 9
C8H18 18
.
.
.
C20H42
366,319

42. What is the chemical formula for the following structure?
A. C3H8
B. C4H10
C. C5H12
D. C6H14
Line formula for: C3H8

43. Organic chemistry is the branch of chemistry that
deals with carbon compounds.
C
H
H
H OH C
H
H
H NH2 C
H
H
H C OH
O
methanol methylamine acetic acid
Functional Groups: