1

JEE Main 2019 (Online) 10th January Evening Slot

The 71st electron of an element X with an atomic number of 71 enters into the orbital;
A
4f
B
6s
C
6p
D
5d

Explanation

In lutetium (71Lu) the 71st electron enters in 5d-orbital.

Electron configuration is [Xe]4f145d16s2
2

JEE Main 2019 (Online) 11th January Morning Slot

The correct order of the atomic radii of C, Cs, Al, and S is :
A
S < C < Al < Cs
B
S < C < Cs < Al
C
C < S < Al < Cs
D
C < S < Cs < Al

Explanation

Atomic radii increase by moving down the group and decrease across a period.

Hence, the correct order of atomic radii is : C < S < Al < Cs.
3

JEE Main 2019 (Online) 11th January Evening Slot

The correct option with respect to the Pauling electronegativity values of the element is :
A
Ga < Ge
B
Si < Al
C
Te > Se
D
P > S

Explanation

Electronegativity increases from left to right in a period and decreases down the group. The correct orders are

Si > Al, Ga < Ge, Te < Se and P < S.
4

JEE Main 2019 (Online) 11th January Evening Slot

The relative stability of +1 oxidation state of group 13 elements follows the order :
A
Tl < In < Ga < Al
B
Al < Ga < TI < In
C
AI < Ga < In < TI
D
Ga < AI < In < TI

Explanation

Inert pair effect gradually increases down the group. Hence, stability of lower oxidation state increases down the group.

$\therefore$ AI < Ga < In < TI