Consider the following statements for Allred-Rochow electronegativity (XAR):

(i) XAR is directly proportional to Z_eff.

(ii) XAR is inversely proportional to Zeff.

(iii) XAR is inversely proportional to r(covalent).

(iv) XAR is inversely proportional to r² (covalent).

The correct statements are

The correct answer is ​(i) and (iv)

Concept:

• The Allred-Rochow scale is used for the measurement of electronegativity between two covalently bonded atoms.
• In the Allred-Rochow scale, the electronegativity of an atom is measured in terms of the electrostatic force F exerted by the nucleus of the atom on an electron at a distance of the covalent radius (r_cov) from the nucleus and the effective nuclear charge (Z_eff) of the atom by using the slaters rule for all the electrons in that atom.

Explanation:

• The electrostatic force F can be expressed in terms of effective nuclear charge (Zeff) and the covalent radius (rcov) from the nucleus as follows: 

​.

• Thus, from the Allred-Rochow scale, we get the following statements for Allred-Rochow electronegativity (X_AR): X_AR is directly proportional to Zeff and X_AR is inversely proportional to r2 (covalent).

Conclusion:

• So, the correct statement is ​(i) and (iv).