Question

The atomic number of two elements a and b are 19 and 20 respectively which element exhibit highest metallic property why write the molecular formula of the compound formed element element x having atomic number 17

Answer 1

calcium(atomic number-19) is less active than potassium(atomic number-20).
reason:metals are less reactivethan the neighboring alkali metal. 

when Ca is reacted with chlorine(atomic number-17) then CaCl2 is formed
whereas,when K is reacted with chlorine(atomic number-17) then KCl is formed.

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