Advanced level chemistry lesson notes
Advanced level chemistry lesson notes
Periodicity of Physical and Chemical Properties
Brief history of the periodic table
a) Johann Döbereiner
Early in the nineteenth century (1817) Johann Döbereiner pointed out that the known elements at
the time could be arranged in groups of three similar elements called “triads” two of the Döbereiner
triads were lithium sodium, and potassium (alkali metals) and chlorine, bromine, and iodine
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Various Blocks of the Periodic Table
The periodic table is divided into distinct blocks based on electron configurations. Namely, these are the s-block, the p-block, the d-block, and the f-block.
1. The s-block
The elements of Group I (alkali metals) and Group II (alkaline earth metals) are classified as s-block elements.
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Why are they called the s-block?
Because their outermost (valence) electrons are in the s-sub-shell.
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Key Characteristics:
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The s-block elements are the most reactive metals (most electropositive metals).
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They have lower melting and boiling points than other metals, as well as low ionization energy.
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The maximum number of electrons in the s-orbital is 2.
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2. The p-block
Elements from Group III, IV, V, VI, VII, and VIII make up the p-block.
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Why are they called the p-block?
Because their outermost electrons are in the p-sub-shell.
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Key Characteristics:
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The p-block constitutes mostly non-metals.
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The reactivity of p-block elements changes from moderately active metals in Group III to highly reactive non-metals in Group VII.
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The maximum number of electrons in the p-sub-shell is 6.
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3. The d-block
The d-block elements are positioned between Group II and Group III of the periodic table.
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Why are they called the d-block?
This is because electrons are being added to the inner d-sub-shell across this series of elements.
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Key Characteristics:
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The first row of d-block elements spans from scandium to zinc.
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The d-block elements are significantly less reactive than the metals in Groups I and II.
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The maximum number of electrons in the d-sub-shell (orbital) is 10.
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4. The f-block
The lanthanide and actinide series form the f-block. These elements are also commonly referred to as the inner transition elements.
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Why are they called the f-block?
Because electrons are being added to the f-sub-shell.
Metals, Non-Metals, and Metalloids
The periodic table is broadly divided into metals, non-metals, and metalloids by a distinct, thick step-like line.
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Metals: Elements located to the left of the thick step line.
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Non-Metals: Elements located to the right of the thick step line.
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Metalloids: Elements situated directly next to the thick step line—such as boron, silicon, germanium, arsenic, and antimony.
Note on Metalloids: They are classified as such because they display physical and chemical properties intermediate between those of metals and non-metals. Notably, silicon and germanium function as semiconductors.
