Which property of group 2 elements ( magnesium to barium) and their compounds increases with an increasing proton (atomic) number?
A)the magnitude of the enthalpy change of hydration of the metal ion
B)the pH of the aqueous chloride
C)the solubility of the sulphate in water
D)the stability of the carbonate to heat
E)the tendency to form complex ion ?
Kindly answer this , alongwith the explanation.
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To determine which property of group 2 elements and their compounds increases with an increasing proton (atomic) number, we need to examine the trends across the group.
The group 2 elements include magnesium (atomic number 12), calcium (atomic number 20), strontium (atomic number 38), and barium (atomic number 56).
A) The magnitude of the enthalpy change of hydration of the metal ion:
The enthalpy change of hydration refers to the energy released when water molecules surround and bond to individual metal ions. As we move down group 2, the enthalpy change of hydration generally decreases. This is because as the atomic number increases, the atomic radius and electron shielding also increase, leading to a weaker attraction between the metal cations and water molecules. Therefore, as the proton/atomic number increases, the magnitude of the enthalpy change of hydration decreases.
B) The pH of the aqueous chloride:
Group 2 elements form 2+ cations, and their chlorides are generally soluble in water. When these chlorides dissolve in water, they hydrolyze, resulting in the formation of hydroxide ions and a basic solution. Therefore, as we move down group 2, the pH of the aqueous chloride increases. Hence, as the proton/atomic number increases, the pH of the aqueous chloride increases.
C) The solubility of the sulfate in water:
The solubility of group 2 sulfates generally decreases down the group. This is due to the smaller size and higher charge density of the cation as the atomic number increases. The smaller and more highly charged cations will have a stronger electrostatic attraction to the sulfate ions, making it more difficult for the sulfate ions to dissolve in water. Thus, as the proton/atomic number increases, the solubility of the sulfate in water decreases.
D) The stability of the carbonate to heat:
Group 2 carbonates become less stable to heat with increasing atomic number. As we move down the group, the carbonates decompose more readily upon heating to form oxides and carbon dioxide. This trend occurs because the larger cations have weaker attractions to the carbonate ion, leading to easier decarbonation. So, as the proton/atomic number increases, the stability of the carbonate to heat decreases.
E) The tendency to form complex ions:
Complex ions are formed when metal cations interact with ligands that donate electron pairs. The tendency to form complex ions generally increases down group 2 because larger cations have more vacant orbitals available for bonding. Therefore, as the proton/atomic number increases, the tendency to form complex ions also increases.
In summary, the property of group 2 elements and their compounds that increases with an increasing proton (atomic) number is:
E) The tendency to form complex ions.