Group 2

The group 2 elements each have...

• 2 e- in an outer s-orbital

• 2 e- each in outer s- and p-orbitals

• 2 e- in an outer p-orbital

• 2 e- in an outer d-orbital

Group 2 melting points...

• increases down the group as atomic size increases

• decreases down the group as atomic size decreases

• decreases down the group as atomic size increases

• increases down the group as atomic size decreases

Magnesium reacts slowly with cold water as follows...

• Mg + H2O → MgO + H2

• 2Mg + 2H2O → 2MgOH + H2

• Mg + 2H2O → MgO2 + 2H2

• Mg + 2H2O → Mg(OH)2 + H2

The most insoluble hydroxide in group 2 is...

• Ca(OH)2

• Ba(OH)2

• Sr(OH)2

• Mg(OH)2

Which one of these is not a medical use of group 2 compounds...

• Barium meal

• Scrubbing SO2

• Antacid

• Radium radiotherapy

Which group 2 ion is used in the standard test for sulphates?

• Mg2+

• Sr2+

• Ca2+

• Ba2+

Which reaction shows the strong heating of magnesium nitrate?

• Mg(NO₃)₂ --> Mg(NO₂)₂ + O₂

• Mg(NO₃)₂ -->MgO₂ + 2NO₂

• Mg(NO₃)₂ --> MgO + N₂O + 2O₂

• 2Mg(NO₃)₂ --> 2MgO + 4NO₂ + O₂

The table shows the decomposition temperature of the carbonates of Group 2 elements.

Why is BeCO₃ unstable thermally?

• The electron cloud of the Be²⁺ ion is polarised by the CO₃^2– ion.

• The electron cloud of the CO₃^2– ion is polarised by the Be²⁺ ion.

• Going down Group 2, the size of the cation increases and the polarisation of the anion by the cation becomes greater.

• A small cation absorbs energy more efficiently and can be excited to a higher energy level which is unstable.

The solubilities of the sulphates of Group 2 metals decrease down the group because

• the cation size increases from Mg²⁺ to Ba²⁺

• the hydration energy of the cations becomes less exothermic from Mg²⁺ to Ba²⁺

• the sulphates ion very much smaller than these cations.

The carbonates, nitrates and hydroxides of Group 2 elements decompose to their respective oxides when heated. Hence, it can be concluded that

• all compounds of Group 2 elements are unstable to heat

• Group 2 elements are strong reducing agents

• the oxide is energetically more stable than the carbonates, nitrates and hydroxides

• the metallic properties of the elements increases down the Group