281.

Which of the following has largest atomic radii ?

• Al

• Al⁺

• Al²⁺

• Al³⁺

Ionisation potential is lowest for :

• alkali metals

• inert gases

• halogens

• alkaline earth metals

Maximum number of unpaired electrons are present in

• Gd³⁺

• Yb²⁺

• Tb²⁺

• Pm³⁺

Which of the following is correct?

• Ionic radius is proportional to atomic number.

• Ionic radius is inversely proportional to atomic mass.

• Ionic radius is inversely proportional to effective nuclear charge.

• All are correct.

Beryllium and aluminium exhibit many properties which are similar. But the two elements differ in

• maximum covalency in compounds

• exhibiting amphoteric nature in their oxides

• forming covalent halides

• forming polymeric hydrides

Assertion : Helium is used in diving apparatus.

Reason : Solubility of helium is less in blood.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.

Assertion : The position of an element in periodic table after emission of one $\mathrm{\alpha }-$ and two $\mathrm{\beta }$- particles remains unchanged.

Reason : Emission of one $\mathrm{\alpha }-$ and two $\mathrm{\beta }-$particles give isotope of the element which acquires same position in periodic table

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Mercurous chloride exists in the form of

• Hg⁺

• Hg₂²⁺

• Hg²⁺

• Hg₃²⁺

Incorrect statement about Ge is

• GeO₂ is weakly acidic

• Ge(OH)₂ is amphoteric

• GeCl₂ is more stable than GeCl₄

• Ge-Ge bond energy is lesser than that of Si - Si.

Among third row elements , the IP value :

• irregularly changes from left to right across the third row

• increases from left to right across the third row

• decrease for Na to Ar

• remains constant