Periodic classification questions | form five Chemistry

State the reason(s) for the following facts;

1. Although Na⁺, Mg²⁺ and Al³⁺ ions have the same electronic configuration, they have different radii.
2. At ordinary temperature , phosphorus pentachloride (PCl₅) is a white solid with unexpected high melting point.
3. Sodium chloride (NaCl) and unhydrous aluminium chloride (AlCl₃) are both chlorides of metals of period (III). Molten sodium chloride can be electrolysed while molten unhydrous aluminium chloride can not.
4. The first ionization energy increases from left to right across a period but the first ionization energy of magnesium is larger than that of aluminium.
5. Lithium and potassium are metals of group (I). In aqueoues solution, lithium is a poor conductor of electricity while potassium is a good conductor.
6. Boiling point of water (H₂O) is higher than that of hydrogen sulphide (H₂S). All are hydrides of group (IV) elements.

Answer / Solution

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