Class 11th

(a) P (Z=15) : [Ne]¹⁰3s²3p³  No. of unpaired electrons = 3
(b) Si (Z=14) : [Ne]¹⁰3s²3p²  No. of unpaired electrons = 2
(c) Cr (Z=24): [Ar]¹⁸4s¹3d⁵  No. of unpaired electrons = 6
(d) Fe (Z=26): [Ar]¹⁸4s²3d⁶  No. of unpaired electrons = 4
(e) Kr (Z=36) : [Ar]¹⁸4s²3d¹⁰4p⁶  No. of unpaired electrons = Nil.

Configuration of the two elements are:

Al (Z = 13): [Ne]¹⁰3s²3p¹

Si (Z = 14): [Ne]¹⁰3s²3p²
The unpaired electrons in silicon (Si) will experience more effective nuclear charge because the atomic number of the element Si is more than that of Al.

This is a short answer type question as classified in NCERT Exemplar

Greater the penetration of the electron present in a particular orbital towards the nucleus more will be the magnitude of the effective nuclear charge. Based upon this

(i) 2s orbital is closer to the nucleus than 3s orbital and hence it will experience more effective nuclear charge.

(ii) 4d orbital will experience more effective nuclear charge due to its closer proximity to 4f orbital.

(iii) 3p orbital will experience more effective nuclear charge as it is closer to the nucleus

This is a short answer type question as classified in NCERT Exemplar

The nitro group strongly deactivate the benzene towards the electrophilic substitution reaction due to the -R and -I effect

The nuclear charge experienced by electrons depends on the distance between the nucleus and orbital. The greater is this distance, the lesser is the effective nuclear charge. Among all the p orbitals, 4p orbital lies the farthest from the nucleus and thus experiences the lowest effective nuclear charge because of the maximum magnitude of screening or shielding effect.

This is a short answer type question as classified in NCERT Exemplar

Due to the +R effect halogens are ortho and para directing groups.

The electrons may be assigned to the following orbitals :
(i) 4d
(ii) 3d
(iii) 4p
(iv) 3d
(v) 3p
(vi) 4p.
The increasing order of energy is :
(v) < (ii) = (iv) < (vi) = (iii) < (i)

Since actual momentum is smaller than the uncertainty in measuring momentum, therefore, the momentum of electron cannot be defined

This is a short answer type question as classified in NCERT Exemplar

The electron donating group increases the reactivity in electrophilic substitution reaction whereas the electron withdrawing group decreases the reactivity in electrophilic substitution.

Thus, the order of reactivity