Write the names and symbols of two most reactive metals belonging to group I of the periodic table. Explain by drawing electronic structure how either one of the two metals reacts with a halogen. With which name is the bond formed between these elements known and what is the class of the compound so formed known? State any four physical properties of such compounds.

Most reactive metals belonging to group I of the periodic table are Sodium and Potassium. Their symbols are “Na” and “K”.


Electron dot structure – valence electrons are represented by dots placed around the chemical symbol. Electrons are placed up to two on each side of the elemental symbol for a maximum of eight, which is the number of electrons in a filled s and p shell. We place a single electron on each side before pairing them up (this is related to Hund’s rule). Period one (hydrogen and helium) represents an exception where only a maximum of two electrons are placed on one side of the element.


Electron dot structure for sodium:


Reaction of Na with halogen (eg: Chlorine)


Formation of sodium chloride:


STEP 1: Formation of cation-


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STEP 2: Formation of anion-


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STEP 3: Formation of NaCl-


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Properties of NaCl:


• This compound is a solid and is somewhat hard because of strong force of attraction between the positive- positive ions. It is generally brittle and breaks into pieces when pressure is applied.


• NaCl has high melting and boiling point because a considerable amount of energy is required to break the strong inter-ionic attraction.


• It is generally soluble in water.


• It conducts electricity in molten state because the movement of ions is possible.


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