Test: JEE Main 35 Year PYQs- Classification of Elements & Periodicity in Properties - JEE MCQ

According to modern periodic law, the properties of the elements are repeated after certain regular intervals when these elements are arranged in order of their increasing atomic numbers.

Na₂O (basic), SO₂ and B₂O₃ (acidic) and Zn O is amphoteric.

O^{– –} and F^– are isoelectronic. Hence have same number of shells, therefore greater the nuclear charge smaller will be the size i.e.
O^{– –} > F^–
further Li⁺ and B³⁺ are isoelectronic. therefore Li⁺  >  B³⁺ Hence the correct order of atomic size is.
O^-- > F^– > Li⁺ > B³⁺

As the size increases the basic nature of oxides changes to acidic nature i.e., acidic nature increases.

SO₂ and P₂O₃ are acidic as their corresponding acids H₂SO₃ and H₃PO₃ are strong acids.

O^– ion exerts a force of repulsion on the incoming electron. The energy is required to overcome it.

CaO is basic as it form strong base Ca(OH)₂ on reaction with water.
CaO + H₂O –––––→ Ca(OH)₂ CO₂ is acidic as it dissolve in water forming unstable carbonic acid.
H₂O + CO₂ –––––→ H₂CO₃
Silica (SiO₂) is insoluble in water and acts as a  very weak acid.
SnO₂ is amphoteric as it reacts with both acid and base.
SnO₂ + 2H₂SO₄–––––→ Sn(SO₄)₂ + 2H₂O SnO₂ + 2KOH–––––→ K₂SnO₃ + H₂O

In a period the value of ionisation potential increases from left to right with breaks where the atoms have some what stable configuration. In this case N has half filled stable orbitals. Hence has highest ionisation energy. Thus the correct order is
B < C < O < N
and not as given in option (c)

The alkali metals are highly reactive because their first ionisation potential is very low and hence they have great tendency to loses electron to form unipositive ion.
NOTE : On moving down group- I from Li to Cs ionisation enthalpy decreases hence the reactivity increases. The halogens are most reactive elements due to their low bond dissociation energy, high electron affinity and high enthalpy of hydration of halide ion.
However their reactivity decreases with increase in atomic number

(a,c) As we move from top to bottom in a group, the acidic strength of hydrides increases. Therefore, order of acidic strength of hydrides of VA and VII A group elements is

NH₃ < PH₃ < AsH₃< SbH₃
HF<HCl < HBr <HI
 

b) As we move from top to bottom in a group acidic nature (K_a) increases. Therefore, pK_a decreases. Thus, order of pK_a value of hydrides of VI A group  elements is
H₂O > H₂S >H₂Se > H₂Te

d) On moving from top to bottom, oxidising power of oxides increases. Thus, order of oxidising power of oxides of IVA group elements is 
CO₂ < SiO₂ < SnO₂ < PbO₂

(a,c) As we move from top to bottom in a group, the acidic strength of hydrides increases. Therefore, order of acidic strength of hydrides of VA and VII A group elements is

NH₃ < PH₃ < AsH₃< SbH₃
HF<HCl < HBr <HI
 

b) As we move from top to bottom in a group acidic nature (K_a) increases. Therefore, pK_a decreases. Thus, order of pK_a value of hydrides of VI A group  elements is
H₂O > H₂S >H₂Se > H₂Te

d) On moving from top to bottom, oxidising power of oxides increases. Thus, order of oxidising power of oxides of IVA group elements is 
CO₂ < SiO₂ < SnO₂ < PbO₂

A ll the given species con tain s 10 e^– each i . e. isoelectronic.
For isoelectronic species anion having high negative charge is largest  in size and the cation having high positive charge is smallest.

On moving across a period ionisation energy increases hence the electropositive nature of metals decreases therefore the ease of formation of ion also decreases and hence the basic character decreases. Further basic character of alkali metals oxides increases from Li₂O to Cs₂O. Hence the correct order will be Al₂O₃ < MgO < Na₂O < K₂O

Among isoelectronic species ionic radii increases as the charge increases.
Order of ionic radii Ca²⁺ < K⁺ < Cl^– < S^2– The number of electrons remains the same but nuclear charge increases with increase in the atomic number causing decrease in size.

On moving along a period from left to r ight I.E. increases and on moving down a group I.E. decreases. hence correct order is : Ba < Ca < Se < S < Ar

(because the reaction is reverse)

For isoelectronic species, size of anion increases as negative charge increases. Thus the correct order is