NTA Abhyas JEE Main2020ChemistryClassification of Elements and Periodicity in PropertiesPractice
Which of the following orders is incorrect with respect to the property indicated ?
Options
- ANH 3 < PH 3 < AsH 3 (acidic behaviour)
- BLi < Be < B < C (first ionisation energy)
- CAl 2 O 3 < MgO < Na 2 O < K 2 O (basic character)
- DLi + < Na + < K + < Cs + (ionic radius)
Correct answer
B. Li < Be < B < C (first ionisation energy)
Step-by-step solution
(i) Bond angle of NH 3 = 107 o PH 3   >   AsH 3 = 90 o According to bond angle the %s character of lp in NH 3 = 22 % while in PH 3 & AsH 3 having approximately 100%, so the donation of lp in PH 3 & AsH 3 are difficult. Hence, the acidic character increases and the order of acidic character is NH 3 < PH 3 < AsH 3 is correct (ii) On moving left to right in a period ionisation energy increases. Li < Be < B < C but the first ionisation potential of Be is higher than that of B because Be has fulfill