Periodic Table & Periodicity JEE Main PYQs, 2020 to 2025

The atomic number of the element from the following with lowest 1^st ionisation enthalpy is :

Choose the incorrect trend in the atomic radii (r) of the elements.

Electronic configuration of four elements A, B, C and D are given below :

(A) $1 s^2 2 s^2 2 p^3$

(B) $1 s^2 2 s^2 2 p^4$

(C) $1 s^2 2 s^2 2 p^5$

(D) $1 s^2 2 s^2 2 p^2$

Which of the following is the correct order of increasing electronegativity (Pauling's scale)?

Given below are two statements :

Statement (I) : The radii of isoelectronic species increases in the order.

Mg²⁺ < Na⁺ < F^$-$ < O^2-

Statement (II) : The magnitude of electron gain enthalpy of halogen decreases in the order.

Cl > F > Br > I

In the light of the above statements, choose the most appropriate answer from the options given below :

Given below are two statements :

Statement I : According to the Law of Octaves, the elements were arranged in the increasing order of their atomic number.

Statement II : Meyer observed a periodically repeated pattern upon plotting physical properties of certain elements against their respective atomic numbers.

In the light of the above statements, choose the correct answer from the options given below :

Number of elements from the following that CANNOT form compounds with valencies which match with their respective group valencies is ________. B, C, N, S, O, F, P, Al, Si