STPM Inorganic Group 2 elements

The carbonate of a Group 2 element (beryllium to barium) in the Periodic Table, MCO₃, decomposes on heating. Which of the following explains why the thermal stability of MCO₃ increases down Group 2? [2005, Q25]

• The radius of M²⁺ ion increases

• The lattice energy of MCO₃ decreases

• The charge density of M²⁺ ion decreases

• The distance between M²⁺ and CO₃^2- ions increases.

Strontium is an element in Group 2 of the Periodic Table which is situated between calcium and barium. Which statement is true?

• The strontium ion has a higher charge density than the calcium ion

• Strontium sulphate is less soluble in water than calcium sulphate.

• Strontium carbonate is more difficult to decompose than barium carbonate when heated

• Strontium nitrate is more difficult to decompose than barium nitrate when heated

Which statement best explains why the thermal stability of the carbonates of Group 2 metals of the Periodic Table increases going down the group? [2009, Q20]

• The polarisation power of the metal ion towards the CO₃^2- ion decreases.

• The strength of ionic bond in the metal carbonate increases.

• The radius of the metal ion increases.

• The electronegativity of the metal decreases.

When aqueous solutions of barium nitrate and sodium sulphate are mixed, a white precipitate of barium sulphate is formed. Which statement explains why barium sulphate is precipitated from the reaction mixture? [2013 U2, Q10]

• Its ions are large

• It is an ionic compound with covalent character

• Its enthalpy of hydration is lower than its lattice energy

• It has a high solubility product

Which element has a value of electronegativity closer to aluminium? [2013 U2, Q11]

• Beryllium

• Magnesium

• Strontium

• Barium