Test: Anomalous Behaviour: s-Block Elements (Old NCERT) - JEE MCQ

Due to the formation of a protective oxide layer on the surface of Be, its reactivity with acids decreases.

The electronic configuration of Be is 1s²2s². We can see that there are only 4 orbitals in its valence shell( they are s and p). In other words, d orbital is absent. So, Be shows ccoordination no 4 and not 6 as like other members of its group.

Be and Al compounds are largely covalent because of high charge density leading to high polarizing power of the cations.

Chlorides of both Li and Mg are deliquescent (absorb moisture from surroundings) and soluble in alcohol and pyridine. Lithium chloride, like magnesium chloride (MgCl₂.6H₂O) separates out from hydrated crystal LiCl.2H₂O.

Due to diagonal relationship, Li resembles Mg.

Be shows anomalous behaviour because of small size, high ionization enthalpy and non availablilty of d orbitals.

Be and Al forms compound with Cl as BeCl

Correct option is C. Due to high polarisation power of Li, it takes oxygen atom from going CO₃^2- to form Li₂O. However. The reaction of Na is a general reaction. Rest other GI forms Nitrite on heating of their Nitrate.

Fluorine forms molecules with fourteen metals because its small size and single charge as an ion allows surrounding metal atoms with more fluorines than oxygen.

BeO is amphoteric as it can react with both acids and base
BeO₊₂NaOH = Na₂BeO₂
BeO+H₂SO₄ + BeSO₄ + H₂O
On the other hand, MgO and Cao are metallic oxides and act as a base only.