Ionic radii vary with respect to the following factors:

a. Inversely proportional to the effective nuclear charge.
b. Directly proportional to the effective nuclear charge.
c. Directly proportional to the screening effect.
d. Inversely proportional to the screening effect.

Which of the following pairs of statements is/are correct?
1. a and c
2. c and d
3. a and b
4. b and d

The order of screening effect of electrons of s, p, d and f orbitals of a given shell of an atom on electrons in its outer shell is :

1. s > p > d > f

2. f > d > p > s

3. p < d < f < s

4. f > p > s > d

Which of the following correctly represents the order of electron gain enthalpy
(energy released on gaining an electron) among halogens?

In the modern periodic table, the period number directly signifies which of the following characteristics for the elements belonging to that period?

The elements in which electrons are progressively filled in 4f-orbitals are called:

The correct order of size of the given species is: 

Which of the following represents the valence shell electronic configuration of the last element of p-block, located in the 6th period?

1. $7{\mathrm{s}}^{2}7{\mathrm{p}}^6$

2. $5{\mathrm{f}}^{14}6{\mathrm{d}}^{10}7{\mathrm{s}}^{2}7{\mathrm{p}}^0$

3. $4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}6{\mathrm{s}}^{2}6{\mathrm{p}}^6$

4. $4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}6{\mathrm{s}}^{2}6{\mathrm{p}}^4$

The elements with atomic numbers 35, 53, and 85 are: