all r not absolutely right .........................

now look,

1) inert pair effect  is reluctance of ELECTRONS of s orbital to move out of the shell ,

this is because of 2 options :

   a) s orbitals is very close to nucleus and therefore due to higher coulombic charge , they r very difficult to remove

b) higher SCREENING EFFECT CAUSED BY Selectrons than others

( understood)

 

2)

 N(SiH3)3 is planar  because SI IS PRESENT IN SECOND PERIOD , THEREFORE IT HAS D ORBITALS LEFT AND THEREFORE

LONE PAIR OF N2 r transferred to Si,

therefore planar

but in N(ch3)3  u know CARBON HAS NO D-ORBITALS LEFT...........................THERFORE PYRAMIDAL ...............

NOW U SHOULD HAVE UNDERSTOOD ..

THANKU