Periodic Properties of the Elements. Magnetic Properties. Reducing Ability of Group 1 and 2 Metals. Acid Base Nature of Element Oxides

1. Periodic Properties of the Elements
Dr. K. Shahzad Baig
Memorial University of Newfoundland (MUN)
Canada
Petrucci, et al. 2011. General Chemistry: Principles and Modern Applications. Pearson Canada Inc., Toronto, Ontario.
Tro, N.J. 2010. Principles of Chemistry. : a molecular approach. Pearson Education, Inc

2. Periodic Properties of the Elements
The atomic radius of Sr is
greater than that of Mg;
both elements are in group 2
The first ionization energy of
P is greater than that of Mg;
both elements are in
3rd period
However, comparing elements
that are not within the same
group or period can be
difficult.(e.g. Mg vs I)

3. Magnatic Properties
• Paramagnetic atoms or ions:
– Unpaired e-.
– Attracted to an external magnetic field.
• Diamagnetic atoms or ions:
– All e- are paired.
– Weakly repelled by a magnetic
field.

4. Paramagnetism

5. Boiling Point
The value of a property often changes uniformly
from the top to the bottom of a group of
elements in the periodic table.
Cl Br I

6. Melting Points of Elements
Sometimes the trend in a property reverses
direction within a period, For example
Melting point
The metals Na, Mg, and Al have
good thermal and electrical
conductivities. The metalloid Si is
only a fair conductor of heat and
electricity, while the nonmetals P,
S, Cl, and Ar are poor conductors.

7. Melting Points of Compounds
The property of hardness also depends on forces
between atoms and molecules in a solid. So the
hardness of the solid third-period elements varies in
much the same way as their melting points.
The bonds between atoms within molecules are
strong, but intermolecular forces, the attractive
forces between molecules, become progressively
weaker across the period, and the melting points
decrease
Ar atoms do not form molecules, and the forces
between Ar atoms in solid argon are especially
weak. The melting point of Ar is the lowest for the
entire period (84 K).

8. Reducing Ability of Group 1 and 2 Metals
2 K(s) + 2 H2O (l) → 2 K+ (aq) + 2 OH- (aq) + H2(g)
I1, K = 419 kJ
Ca(s) + 2 H2O(l) → Ca2+ + 2 OH- + H2(g)
The lower the energy requirement for extracting electrons the lower the ionization energy
the better the metal is as a reducing agent and the more vigorous its reaction with water.
For example: Potassium and Calcium
I1, Ca = 590 kJ
I2, Ca = 1145 kJ
Potassium reacts more vigorously with water than Calcium

9. Oxidizing Abilities of the Halogens
2 Na + Cl2 → 2 NaCl
Cl2 + 2 I- → 2 Cl- + I2

10. Acid Base Nature of Element Oxides
• Na2O and MgO yield basic solutions [metal oxides at the left of the 3rd period]
• Cl2O, SO2 and P4O10 yield acidic solutions [nonmetal oxides at right of period]
• SiO2 dissolves in strong base, acidic oxide. [where the changeover occur]
Some metal oxides, such as react with water to produce the metal hydroxide
𝐿𝑖2 𝑂 𝑠 + 𝐻2 𝑂 𝑙 → 2 𝐿𝑖+
𝑎𝑞 + 2𝑂𝐻−
𝑎𝑞
Basic oxide Lithium hydroxide
Moving from top to bottom down a group, the elements become more metallic, and their
oxides become more basic.
Some nonmetal oxides react with water to produce an acidic solution. These are acidic
oxides or acid anhydrides
𝑆𝑂2 𝑔 𝑛𝑛𝑛 + 𝐻2 𝑂 𝑙 → 𝐻2 𝑆𝑂3 𝑎𝑞
Acidic oxide Sulfurous acid

11. Aluminum, can act as either an acidic or a basic oxide.
𝐴𝑙2 𝑂3 𝑠 + 6𝐻𝐶𝑙 𝑎𝑞 → 2𝐴𝑙𝐶𝑙3 𝑎𝑞 + 3 𝐻2 𝑂 𝑙
Base Acid
𝐴𝑙2 𝑂3 𝑠 + 2𝑁𝑎𝑂𝐻 𝑎𝑞 + 3𝐻2 𝑂 𝑙 → 2 𝑁𝑎 𝐴𝑙 𝑂𝐻 4 𝑎𝑞
Acid Base Sodium aluminate
The amphoterism of 𝐴𝑙2 𝑂3 signifies the point at which a changeover from basic to
acidic oxides occurs in the 3rd period of elements.

12. Focus on The Periodic Law and Mercury
• Should be a solid.
• Relativistic shrinking
of s-orbitals affects all
heavy metals but is
maximum with Hg.